The rapid development of the industries requires adequate changes on the part of the management models in the construction industry. Open international markets for goods and labor are generally changing the environment in which business is growing. In this regard, in addition to the traditional managerial qualities directly related to construction activities, more and more attention is being paid to personal ones. At the forefront in compiling and implementing the goals of management structures are balanced work between participants in the investment process, motivational forms to increase productivity, rapidly changing conjuncture, dynamic competition, complex organizational systems at the company level.

Attributes of construction management

The main attributes for achieving a successful business model can be grouped into three groups:

  • correctness;
  • ability to communicate between high level participants;
  • clear vision of the current state of the company and the industry on the basis of which a good business plan is set

Correctness applies to all industries. In construction, it is the most sought after among the leaders in the process and is considered a major difficulty that needs to be addressed in the future.
Communication between the participants has always played a key role in the successful implementation of the project. In the presence of high competition, it is wrong to rely solely on the advertising business and communication technologies. Personal contact remains a key tool for building trust between the parties. Underestimation of this element leads to very negative consequences.
The last element is poorly represented in the scientific literature in construction. Despite its fundamentality, it is often overlooked in practice. The management staff of the companies has the ability to often focus and adapt to the needs of the specific client. Those who follow this principle have a better chance of long-term success.

The face of the building manager is changing and seems to lag slightly behind the dynamic environment in construction.

Its traditional qualities lose or diminish their significance at the expense of others. As part of the main problems that need to be addressed, the following can be mentioned:

  • the last 50 years, worldwide, have seen the entry of new figures in the management of the construction process. Often their positions are opposing. For the successful completion of the project, the construction manager can resolve the situation through many techniques, such as: through direct confrontation, a balanced solution or as a mediator between the parties to the dispute. A good construction manager should circumvent the initial confrontation and guide the participants to a balanced solution. The need for good communication skills in this case is key.

  • the focus of the activities performed by the construction manager is gradually shifting. In the past, his main responsibilities have been focused on short-term and long-term site planning and needs. Subsequently, the purely communicative qualities of the individual, his ability to deal with different in nature and interests investors, architects, engineers, financial and government institutions, etc. begin to take precedence. Linguistic, interpersonal and intrapersonal intelligence are increasingly in demand, as the main qualities of project managers.

  • the lack of collaboration between the business part and higher education institutions. Underestimation of opportunities on both sides, lack of trust between them, poor funding of universities, cumbersome education system, low starting salaries are part of the prerequisites for a lack of synchronicity between the training of future civil engineers and the required qualities in the labor market. Episodic attempts to overcome this barrier are not enough. A comprehensive and long-term concept needs to be created aimed at updating the curriculum and the methodologies for its teaching. The evaluation of this concept should be based on clear and measurable criteria.

Despite the highly changing situation in the construction industry, it should not be assumed that all the traditional qualities of management staff are obsolete and have no place in the modern look of the profession. Rather, it is appropriate to talk about a change of focus and the addition of future skills and competencies. Some of the necessary changes are related to:

  • reducing the importance of a clear idea of ​​the capabilities and appetites of competing companies in the industry;

  • lack of opportunity for development of staff from the initial level to the highest positions in the company. The average duration of employment in construction is about 1.5 years;

  • impossibility for close specialization of the companies and construction managers. Companies and specialists offering the realization of the construction undertaking from the phase of the research activities to the full completion of the investment project are increasingly sought;

  • for small companies and sites there is more effort to improve the quality of the final product, stable partnerships between companies performing various types of activities with the idea of ​​comprehensive implementation of complex projects;

  • in addition to the necessary broad knowledge, the requirement to go into details regarding materials, technologies, applicability, expediency is added;

  • insight into the "big picture" uniting the project, its participants and possible obstacles in the implementation of each stage;

  • there are less and less "mandatory" knowledge, skills and experience of managers, at the expense of their balanced qualities - a guarantee of a successful end.

What are the global trends in the industry?

Management companies worldwide are constantly increasing their requirements for project managers. Realizing the need for knowledge not only in the depth of the problems, but also in a wide range of types of construction activities, they purposefully choose specialists with different interests. Of particular importance is the insight into the profile of the individual staff, its proper positioning in the company and determining the direction of its career development.
The staff that best fits the changing environment has significant advantages over their competitors in the market. Due to their insufficient number, there is a serious struggle to attract, retain and develop them. The business in Bulgaria lags behind these trends, which leads to an outflow of quality specialists to work abroad or other, better financially secured industries.

What can / should be done at the company level?

The setting of long-term goals in each construction company must correspond to its presentation to the client. In this regard, the persons of the company, namely its staff, should be familiar with the strategy and share the views of management. Despite the many benefits of such an approach, it is not always applicable, mainly due to the need for an adequate, individual company system for staff selection, commitment to each employee, his understanding, development and inclusion in the common goal.

Author: Dr. Eng. Teodor Todorov



The owners of an abandoned farm in the Netherlands decided to breathe new life into the old building. Preserving entirely the external facade and the surrounding spaces, they focus on the transformation of the internal areas of the building built in 1893. construction.



The main challenge in the reconstruction of the old farm is to achieve a complete symbiosis in architectural terms between an office and a family home in the volume of a large building. Following the needs of the family business, they rely on simple solutions and open spaces, leaving 220 square meters. open office space without internal partitions.


An example of the full utilization of the materials from the original construction is the transformation of floorboards into naturally aged wall elements. Concealing the newly built partition walls for the second floor, they are combined with the old masonry from the interior of the farm.


The large original south-facing wooden doors have also been preserved, with automatic sliding glass partitions added on the inside. Thus, the architects, owners of the building, provide natural light during the cold Dutch months. Prior to the reconstruction, the old farm did not have thermal insulation coatings. In the renovated building, they are placed entirely on the inside of the premises, and the original masonry can only be seen behind the sliding doors and the inner wall of the staircase.



The biggest structural changes were made with the horizontal separation of the two residential floors from the one-storey farm. The total built-up area remains 330 square meters, and the additional division adds another 110 square meters. designed for bedrooms, living room and three wet rooms on the second floor. The stairs and the wet rooms are inserted as a separate volume separating the architectural studio and the living areas, giving an additional feeling of autonomy to the occupants.


The sloping roof of the old farm completely renovated and additionally equipped with dormers and thermal insulation create coziness in the four bedrooms.



The lower living floor, consisting of a kitchen, living room and bathrooms, features a combination of visible trim and modern design. The walls are completely new, allowing the solution of a modern layout and full functionality of the premises. The office areas and the bathrooms for them are completely separated from those intended for the inhabitants of the farm.




"Architecture begins where engineering ends"

The famous quote by the German architect Walter Gropius is just one of the many points of view related to the intersection or absence of such between two key professions in the construction industry. Over the years, the relationship between architects and engineers has often been strained. While architects unleash their creative nuances and strive to bring the environment to their physical limit, it is the engineers who "cut the projects." Structural and technological constraints, as well as financial pragmatism, have often led to misunderstandings.

Left: Jørn Utzon's initial proposal for the Sydney Opera House; Right: The finished building, designed in collaboration with engineers at Ove Arup

In reality, however, it turns out that people from both professions rely on each other to realize their ideas. When they work together, we witness the emergence of unusual construction projects that have become emblems of entire cities. Sometimes even for countries. The construction of the Sydney Opera House, with its bizarre "shells", became possible only after the joint work of architect Jorn Utzon and the engineers of Ow Arup.
It was also entirely possible for a tower in the heart of Paris not to leave the drawing board. It became a fact thanks to the precise design adaptations of Gustav Eiffel.

Left: original design by Maurice Coeschlin; Right: Gustav Eiffel's final design

Although the relationship between architects and engineers is always accompanied by very strong positive and negative feelings between them, the best staff in these two professions understand and appreciate the qualities and strengths of their colleagues. Beyond these two iconic projects in Sydney and Paris, in this article we will introduce you to eight impressive projects that became possible after the symbiosis between the two seemingly opposite professions. These projects show how behind every spectacular architectural project are civil engineers, ensuring its seemingly impossible realization.

Busan Cinema Center during construction

Finished the glowing "flying roof" of Busan Cinema Center 

The Austrian company Coop Himmelb is working with civil engineers at Bollinger § Grohmann to build the huge "flying roof" of the Busan cinema. The mysterious "canopy", which houses much of the cultural program for mixed use of the building, is widely known as the largest structural console in the world.

architects: Coop Himmelb (l) au
engineers: Bollinger + Grohmann

Beginning of construction for Canton Tower

In the evening, Canton Tower serves as a starting point for the entire city 

The tower offers a unique experience
At 610 meters high, Canton Tower is currently the fifth tallest building in the world. It is also the main attraction in the skyline of Guangzhou, China. The twisted steel structure of the building, called "Supermodel" by the locals, was designed by Mark Hemel in collaboration with the engineering giants from Arup.
Canton Tower, Guangzhou, China
architects: Information Based Architecture
engineers: Arup Associates

Interlace during construction

The completed project in Singapore

Ole Scherence's remarkable residential building consists of a series of huge, multi-storey volumes arranged in a chaotic composition, allowing a wide variety of outdoor amenities suitable for Singapore's tropical climate. The large support distances required for this unusual configuration were jointly designed between Arup in Beijing and the well-known local company RSP.

architects: OMA
engineers: Arup Associates and RSP Architects Planners Engineers

Princess Alia International Airport during construction

The airport is in operation
The modular roof panels of the new Foster & Partners terminal at Queen Alia International Airport were designed in collaboration with the civil engineers of the international company BuroHappold. These shallow concrete domes, combined with the supporting columns, are reminiscent of the local palm trees. Thus designed, the bizarre construction has a natural strength that allows large openings to be left for natural light to pass to the heart of the terminal.

architects: Foster & Partners and Maisam Architects and Engineers
engineers: BuroHappold

Kingdom Tower at the beginning of the construction process in 2013

Preview of the completed tower in Jeddah, Saudi Arabia, towering over the clouds
To surpass the Burj Khalifa as the tallest building in the world after 2020, the Royal Tower is being built thanks to the close relationship of the architects with the engineers from Langan International, responsible for site planning and the engineers from Thornton Tomasetti, who were entrusted with the task of the constructive design of the Mega-tall building.

architects: Adrian Smith and Gordon Gill Architecture
engineers: Langan International and Thornton Tomasetti

The Mercedes-Benz stadium is under construction

3D visualization of the completed stadium, Atlanta, USA
The HOK project, which won the Atlanta Falcons new home competition, includes a retractable roof. Its gear shape consists of eight huge, sliding ETFE segments resembling the wings of a bird. The stadium designed in this way remains unaffected by the climatic conditions and thus provides comfort to players and visitors. At the moment, the unique design of the roof is in the process of completion, and the elements are delivered in cooperation with civil engineers from the international company BuroHappold.

architects: HOK
engineers: BuroHappold

Construction of Heydar Aliyev Center, Baku, Azerbaijan

The final vision of the project

The wavy shape of the Heydar Aliyev Center is one of the most emblematic projects of Zaha Hadid's architectural office to date. The distorted shape of the building was made possible by the famous engineering companies Werner Sobeck, AKT and Tuncel Engineers, which together with the architects developed a steel frame. The challenge for constructions is the balance between constructive integrity and dynamic, overflowing aesthetics.

Architect: Zaha Hadid Architects
Engineer: Werner Sobek, AKT and Tuncel Engineers

Embassy Gardens under construction, London, UK

3D visualization of the finished pool
Currently under construction, the London Development Center of Embassy Gardens will take water architecture to new heights - literally. HAL Architects has teamed up with Arup Associates, Eckersley O’Callaghan and aquarium designers Reynolds to design the world’s first fully transparent pool between two buildings. The nearly 25 meter long structure will be made of acrylic panels with a thickness of 3.3 cm. Thus, while pedestrians look up, swimmers will look down on them.

architects: HAL Architects
engineers: Arup Associates and Eckersley O’Callaghan


Concrete is the most widely used building material on earth with an annual production of over 10 billion tons! Its main qualities are high compressive strength and its excellent compatibility with steel.

Steel reinforcement is necessary due to one of its main disadvantages - extremely low tensile strength. Or more precisely, about 10 times less than that of pressure. Thus, standard concrete, without reinforcement, does not withstand high tension, therefore it cannot be bent. For years we have been working on the development of concretes that take more tension. The combination of microfiber fiberspolymers and cement are the main technologies for concrete, bearing significant bending. The second major drawback is the environmental footprint of cement production. In 2020, concrete production generated about 1500 000 000 tons of CO2 emissions.

Now, researchers at Swinburne University have developed a new type of concrete. Not only can it bend better, but it doesn't need cement. This feature significantly reduces its environmental footprint. The improved recipe of the concrete mix requires significantly less energy for the production of materials, as well as reduction of carbon dioxide emissions during production.

The biggest pollutant in concrete production is cement, the "glue" in the concrete mix. The preparation of cement requires extremely high temperatures, of the order of 1450 ⁰C. The production process absorbs huge amounts of energy and releases a lot of greenhouse gases. Of course, the production process of new concrete also requires a certain amount of energy.

Instead of cement, industrial waste products such as fly ash extracted from exhaust gases in coal-fired power plants are used to make it. This geopolymer composition can solidify at room temperature.
The use of such waste products in concrete has been practiced for a long time. With the new technology, however, the team claims that this is the first time it has been used in concrete, allowing significant tension and bending. The resulting material reduces energy consumption and greenhouse gas emissions during production, while being far more flexible than standard concrete.

"The production of this new concrete requires about 36 percent less energy and emits up to 76 percent less carbon dioxide than conventional flexible concrete made of cement," said Behzad Nematolahi, the study's author. "The results of our laboratory tests show that this new concrete allows about 400 times more bending than commonly used concrete. However, it has similar strength.

And even when the new material finally cracks, the polymer fibers in the mixture continue to absorb the tensile force. The element remains under tension with many small fractures. The team sees application in the construction of buildings in highly seismic areas. Reducing the carbon footprint should help make the new, more expensive material more desirable.

Despite the good performance, questions remain such as the final cost of production, available quantities of raw materials, recyclability, whether it emits harmful emissions during operation and to what extent it is compatible with the still required conventional reinforcement.



About 1,500 earthquakes are registered in Japan annually. The large number of casualties and the financial losses they cause are forcing civil engineers there to look for increasingly innovative and widely applicable solutions.

The textile company Komatsu Seiren decided to invest in a pilot project, which at first glance looks more like artistic decoration. In reality, however, according to its creators, the thin ropes covering the entire building would play a significant role in the next stronger earthquake.

The project is based on the joint efforts of Kengo Kuma engineers and architects. The task of the team is to seismically provide the new showroom and laboratory of the company. For this purpose, they decided to use the high qualities of carbon fiber fiber composites. 1031 such ropes were used in the project implementation. They are the main element of a composite system - a braid of high-strength carbon fiber and epoxy resin. Engineers anchor them securely in the roof and in the ground around the building.

When exposed to an earthquake, the tension in the ropes causes additional forces in the existing structure. To compensate for this, the team calculated and constructed an internal reinforcement system of 2778 carbon reinforcing bars. This system further increases the stability of the building.

The bottom sample of the computer voltage simulation shows the busiest areas. Warm colors indicate places with extreme values ​​for a particular displacement of the structure, shown by the blue arrow.

For the purposes of the project, it was necessary to further strengthen the contact points of the carbon fibers with the structure, as well as to anchor the entire adjacent area around the building. To perform its functions, the carbon "curtain" needs a foundation that "moves" along with the foundations of the building, without mutual movements between them.

Proektŭt e pŭrviyat po roda si i avtorite mu styatat, che ima realna prilozhimost. Nasheto mnenie kato eksperti e, che tova e po-skoro edna reklamna kampaniya, otkolkoto nov, inovativen metod za nadezhdno osiguryavane na sgradite. The project is the first of its kind and its authors say that it has real applicability. Our opinion as experts is that this is more of an advertising campaign than a new, innovative method of reliably securing buildings.

Author: Dr. Eng. Teodor Todorov



The article is an excerpt from the author's publication in a magazine "Bulgarian ethnology" . It is a peer-reviewed edition of Institute of Ethnology and Folklore with Ethnographic Museum при Българска академия на науките. Статията разглежда едни от най-старите запазени къщи на териотрията на България. По-конкретно са анализирани характерни детайли от строителни практики в Габровския регион. В рамките на теренното проучване “Строителните занаяти на Стара планина”, организирано от сдружение "Meshra - traditional knowledge and crafts and ETHER - Ethnographic open-air museum, held in 2018, some of the few remaining authentic, residential buildings have been studied.


Според събраната информация за посетените къщи, тяхната възраст  достига внушителните 
370 gr.! Most of them are in extremely poor condition, partially destroyed. Despite their impressive presence, age and authenticity, the houses do not have the status of cultural monuments. The focus of the article is on the construction practices in the choice of material, its pre-processing, positive and negative sides of the applied construction techniques for this period of construction. A comparison was made between the masonry technology used in the houses visited, other practices applied abroad at that time, and the current understandings enshrined in the current norms for masonry structures. The presented information could serve for the successful restoration of buildings from this period and a deeper understanding of previous construction materials and technologies.

Основните цели в обхвата на конструктивния анализ, са:

 deepening the analysis and expanding the knowledge about the history of the used construction practices in Bulgaria;
• creating a basis for interpreting the knowledge of the builders at that time;
• reaching a level of information sufficient for authentic reproduction and restoration of such type of buildings;
• archiving and preservation of the history of construction from a constructive point of view during the work of the established in 1949. Institute of Urban Planning and Architecture” at the Bulgarian Academy of Sciences (BAS).


Dating of the oldest visited houses

The houses considered within the project were built in the period 1650 - 1900. There are no historical and written data on the beginning of the settlement in the area. Probably this happened after the beginning of the Turkish invasion in the XIV century. Indirect evidence of this thesis is described in "Architecture of the Bulgarian Revival" (Paunova 1975). Stories of local people and specific details of the construction, layout and interior of the houses serve as a more accurate time guide. Examples of dating to the end of the period in question houses of the architectural ensemble in the village of Bozhentsi, Gabrovo region are the disappearance of the verandas after 1900, the hiding of the stairs in the house and their exit to a corridor between bedrooms on both sides. Criteria for the end of the period considered in the field study are the disappearance of the decoration and the lack of utilitarian purpose of the houses after 1900 (Paunova 1975). Their facade appearance is preserved. Dating according to the distribution of the premises can be done indirectly by comparing with archival data for houses in the area from this period. The books "A Brief History of Bulgarian Architecture", 1965 can be used as reference archives; "The Bulgarian House during the Renaissance", 1955 and "Architecture of the Bulgarian Revival" from 1975 (Dimitrov, Yordanov, Kozhuharov, Miyatev, Stoykov, Tonev, Hristov 1965; Zlatev 1965; Paunova 1975). Some of the houses included in the survey, coinciding with the focus of the field research, are Hadjigrigor's house from 1834 in Etropole, Popangelova's and Slaveykova's house in Tryavna, Jongol's house in Koprivshtitsa from the end of the XVIII or the beginning of the XIX century (Dimitrov, Yordanov, Kozhukharov, Miyatev, Stoykov, Tonev, Hristov 1965). Residential sites related to the pre-Renaissance period of late Turkish feudalism, as well as structural features of the roof structures are recreated in "A Brief History of Bulgarian Architecture" (Zlatev 1965). The information is presented mainly with sketches of one or two facades, section, dimensionless sketches of distributions, drawings and low-quality photographs. There are no constructive features. Examples of residential buildings discussed in the book in the Treven region are the house of Manafovi, the village of Bozhentsi and the house of Lazer Matev in the village of Staynovtsi.
More accurate dating of the age of the houses….

See more

Building materials and technologies

The construction of wild houses in Bulgaria before industrialization is based on the maximum use of natural materials in the immediate vicinity of the site. During the construction of the so-called "earth construction" masonry bodies of natural stones, clay, sand, straw, wood - logs and twigs, stone slabs / slate (Georgieva, Angelova, Nikolov 1996: 6-8) are used. Masonry bodies have different physical and chemical properties, shape, size and composition. The role of bricks is performed by both natural stones and pressed clay blocks with meadow plants (straw) included in their composition. The characteristics of extruded clay blocks vary greatly according to many factors. The main ones are grain size and percentage of sand, clay content, humidity during compaction and testing, compaction quality, content of natural fibers - plant and animal, porosity (Neumann 1993 - may be omitted) (Lorenzo Miccoli, Urs Müller & Patrick 2014). For interior cladding material was used…

Повече за добиването на строителните материали, технологията на изпълнение, използваните разтвори, определянето на качествата на глината, влагането на органични примеси,  мeханичните характеристика на зидарията, причини за разрушения в къщите виж

In all the houses visited, the use of diagonals and intermediate horizontals of wood in the walls made of logs and clay or clay bricks was found. As part of the field study, measurements were made looking for a relationship between the dimensions and angles of the intermediate connections. The initial conclusion from them is that the builders complied mainly with…


Повече за технологията за изграждане на вътрешните стени, състава и функциите на мазилките, диагоналите и междинни хоризонтали от дърво, пожароустойчивостта на къщите, виж HERE

Roof constructions

he shales used in the construction are a type of metamorphic rocks, characterized by a thin layered structure with an oriented arrangement (schistosity) of the minerals. They were mined in quarries, and their stratification was achieved by artificial hydration during the winter months…

… Such a roof did not need repairs. Their displacement took place only under strong vibrations, such as the supersonic transitions of military aircraft at a later stage in the life of the houses. It is only nowadays that the structure of the shale is disturbed as a result of the physico-chemical weathering of the stone…

… Typical for the period roofs from the regions of Teteven, Tryavna and Smolyan region are described in the book…

Повече за конструктивното състояние на посетените къщи, бъдещо развитие на извършеното теренно проучване и литературните източници виж HERE

Author: Dr. Eng. Teodor Todorov



What is sustainable building design?

Sustainable design in the construction of new or renovation of old buildings is the maximum optimization of several basic criteria. The ultimate goal is to significantly reduce the environmental footprint that is generated at each stage of the life of buildings - construction, operation, demolition.

The construction of "green" buildings may sound like another ecological cliché. In reality, however, it turns out that it can play an important role in reducing the environmental footprint of human activity. Additional benefits from "green" construction include improved living conditions for these structures and significantly reduced operating costs. Before we look in more detail at the benefits of investing in environmentally friendly construction, let's look at the disadvantages and losses of standard construction. What are the main damages, their size and the stages at which they occur.

How do construction activities affect the environment?

Contrary to popular belief, the damage from construction is not limited to the process of production of construction materials and their use in the site. The final product, namely the finished building, is of great importance for the size of the environmental footprint.
One example of this is the use of hard-to-recycle materials. Their choice has a short-term negative effect. In contrast, however, the choice of heating and air conditioning system can have a negative environmental and financial effect throughout the period of operation.
The following lines will list the most common damages caused directly by the building stock in the world.

Energy consumption

Energy consumption, related to the operation of buildings, represents about 40% of total consumption worldwide.

В САЩ този процент достига впечатляващите 48%, което е почти  половината от общата консумирана енергия.

Generated greenhouse gases

Construction and repairs worldwide generate 17% of total greenhouse gas emissions.

During the operation of the buildings about 30% are released.
According to statistics of U.S. Green Building Council, almost 40% of CO2 emissions in the United States are directly related to the construction sector.

Water consumption

The low price of this resource, where it is still freely available, allows for unnecessarily large consumption. On average, about 14% of water consumption occurs in buildings. The losses on the water supply network in the developed countries are about 12%, and in our country this value is between 50 and 70%.


Used building materials

Modern materials used in construction have a serious environmental impact. Many of them are difficult to recycle or not reusable at all. The extraction of the huge volumes of raw materials needed for production, processing and logistics over long distances make this process one of the biggest polluters today. According to U.S. Green Building Council, about 40% of the extracted raw materials are for the needs of the construction industry.

Waste products and demolition of old buildings

Demolition and repair activities have a significant share in the waste generated by human activity. They are rarely sorted and recycled. According to Eurostat statistics, 35% of waste is due to activities in the construction sector.

In Bulgaria, this process should be regulated by the "Ordinance on construction waste management and use of recycled construction materials", in force since 2012.


Benefits of "green" construction

LEED / Leadership in Energy and Environmental Design / is the most widespread system for assessment and certification of "green" buildings. From there, they provide visual statistics on the benefits and profitability of such an investment.


Obtaining a certificate under this system guarantees accordingly:


25% less energy consumption
11% lower water consumption
19% less maintenance
34% less greenhouse gas emissions
27% higher rating of buildings, according to their occupants. This criterion covers not only the subjective feeling of higher comfort, but also reduces the likelihood of sick building syndrome, responsible for lower working capacity and hospitalization of employees.
-generate significantly less non-recyclable waste
-total costs are reduced by from 9 to 13%
-the value of the building, after reaching the certification criteria, increases by about 4%
-the investment is paid within 7 years


What is "green" construction



Platform to easily search for information on green development

Author: Dr. Eng. Teodor Todorov



What does land mean?

Part of a territory with defined boundaries, according to an act of ownership. Each land property has a unique for the country cadastral identification number. It can be checked on the site of to the Registry Agency. Another useful online tool is

When is a plot of land regulated?

“Regulated land property” (RLE) or “regulated property” is a land property for which an approved detailed development plan has entered into force.

It should specify:

  • borders, access from a street, road or alley;
  • specific purpose;
  • an indicator for the area of ​​the required land (or the area of ​​the land property) for a respective site;
  • indicator for density (percentage) of construction of the regulated land property (P built-up);
  • indicator for intensity of construction of the regulated land property (K int.);
  • indicator for percentage of landscaping of the regulated land property (P landscaping).


According to their purpose, the regulated land properties in the settlements are envisaged as:

  • residential;
  • за обществено ползване;
  • serving;
  • production;
  • warehouses;
  • resort;
  • villas;
  • sports;
  • recreational;
  • with entertainment functions;
  • for parks and gardens;
  • for traffic and transport and others.

When is a land property unregulated?

Unregulated land is a property that is not regulated by a detailed development plan (DDP). Such properties allow a small percentage of construction regulated in ORDINANCE № 2 OF APRIL 10, 1998 ON DEVELOPMENT IN AGRICULTURAL LAND .


What is the concept of total built-up area?

This is the sum of the built-up areas on all floors. The total built-up area does not include economic areas (warehouses for personal use, attics and basements, studios and their adjacent corridors, stairs and those for general use - garbage pipes, subscriber stations, boiler rooms, etc.). The total built-up area includes the entire areas of balconies, loggias and terraces in the above-ground floors, measured by their external outlines, as well as the built-up areas in the attic spaces of the buildings, when there are no attic storage rooms.

What is building density?

Represents the ratio between the sum of the built-up areas of the main and additional construction in relation to the total area of ​​the regulated land property. Building density is presented as a percentage. This indicator can be determined for a neighborhood, development territory or zone, as well as for individual properties.


 What is the built-up area in a regulated plot of land?

The built-up area is considered to be the step of the building at elevation zero along the external outlines of the enclosing walls. It deducts the area of ​​the ventilation shafts and the passages in these outlines. The built-up area does not include the bidding above the plinth of the buildings, terraces, external stairs and stair landings, swimming pools, ramps, garages and other elements up to 1.2 m high from the average level of the adjacent terrain.


What are ideal / common parts of the building?

The ideal parts of a building are areas that are designed for common use by all owners of the property / building.

The common parts of condominium buildings (Art. 38, para. 1 of the Property Act) are:

The land on which the building is built, the yard;
Foundations and external enclosing walls;
Partition walls between dwellings;
Horizontal and vertical communications (stairs and landings to them);
The mezzanines, the elevator shaft, etc.);
The roof, when not divided into separate warehouses or other premises;
The porter's lodge, the subscriber stations and the premises for civil protection;
The external entrance doors of the building and the doors to the common attics and basements;
The main lines of all types of installations and their central installations;
Everything that by its nature serves public use.


Author: Dr. Eng. Teodor Todorov



Causes of leaks in the elevator shaft and garage. Risks to the building as a result and some possible solutions.

For a start, it is good to get acquainted with the purpose of elevator shafts. Apart from being a vertical communication for the flow of people between the floors, they are often the supporting core of a reinforced concrete structure - the so-called earthquake washers. Washers and support columns are located on the dividing lines of the garages, as well as on their bottom. Issues related to the design of vertical load-bearing elements, their implementation and proper operation are of paramount importance for the security of the building! Therefore, they should be considered as a priority, regardless of the purpose of the structure. Compromises in any of the above three stages can lead to severe consequences and even accidents in the future. In our daily lives, however, we often witness leaks in basements, underground parking lots, garages and elevator shafts. The lack of underground waterproofing or its poor performance is the cause of leaks even in newly built buildings. A prerequisite for this is the naturally high level of groundwater in many Bulgarian cities, the reason for the "flooding" of the shafts and flooding of garages and basements.

Due to the location of the elevator shafts, usually around the geometric center of the building, the repair of the external waterproofing in this section becomes practically impossible.

Английски Povecheto firmi predlagat polaganeto na vŭtreshna izolatsiya pod razlichni formi ili dopŭlnitelnoto izgrazhdane na khidroforna uredba. Na prŭv pogled tezi resheniya eliminirat pochti napŭlno problema s vodata, koyato se prosmukva prez stenite i poda. Na praktika obache, te zashtitavat edinstveno asans’ornata uredba, kato dori vloshavat situatsiyata v koyato se namira konstruktsiyata. Visokata vlazhnost s vremeto stava prichina za znachitelno namalyavane na fiziko-mekhanichnite svoĭstva na gradivnite materiali i kompromentira konstruktsiyata. Sŭshto taka predizvikva seriozna koroziya v elementite na asans’ornata uredba. Most companies offer the laying of internal insulation in various forms or the additional construction of a hydrophore system. At first glance, these solutions almost completely eliminate the problem of water seeping through the walls and floor. In practice, however, they only protect the elevator system, even worsening the situation in which the structure is located. High humidity over time causes a significant reduction in the physical and mechanical properties of building materials and compromises the structure. It also causes serious corrosion in the elements of the elevator system.

Additional internal waterproofing

Let's first consider the application of additional, internal waterproofing on the walls and floor. Even qualitatively executed, this waterproofing often does not create sufficient watertightness around the structural connections of the elevator system with the structure - anchors, plates. Not long after, the leak situation repeats itself.

Another major drawback is the sealing of the water inside the load-bearing walls, which are very often earthquake washers. And right at their base, where they are extremely busy. Through the internal waterproofing we artificially create conditions for retention and capillary rise of water in the height of the shaft.

An improved version of the internal waterproofing is the implementation of waterproof screed on the bottom, which prevents the penetration of water between the bottom-wall joint. Pre-impregnation of the walls improves their water tightness and to some extent limits the capillary rise of water.

The implementation of these systems is complex and requires strict monitoring of the implementation technology. The installation of water-swellable tapes and injection hoses increases the reliability and maintainability of this system. It is applied at long leaks and serious degradation of concrete and reinforcement.

 Hydrophore system in the elevator shaft

This method can eliminate the problem of "boiling", but the high humidity in the walls and floor of the structure remains.

As an additional effect of the continuous pumping of water, there is an extraction of calcium hydroxide (portlandite) from the structure of the cement stone (so-called corrosion type 1), as well as sulfate corrosion, which reduces the strength of concrete. It also reduces its hydrogen index (pH), which otherwise prevents corrosion in the reinforcement. This method can be defined as the most undesirable and harmful to the structure.

Local sealing of affected areas with weak concrete

A relatively fast and efficient method is the local sealing of areas affected by strong corrosion in concrete and reinforcement. Weakened concrete is removed, and in cases of affected longitudinal reinforcement, it is necessary to replace it. This is followed by installation of an injection hose, reinforcement, formwork and concreting of the site.

To achieve a watertight barrier, special concrete compositions and strict execution of the work process are used. The implementation of this system carries the risk of killing a high-flow leak during the preparatory activities including the removal of concrete and reinforcement from the affected areas.

What can be done to avoid these undesirable consequences of conventional waterproofing systems?

Here is the place to emphasize the mandatory involvement of a highly qualified specialist both in the research and design activities and during the implementation itself. His participation will ensure the successful and safe solution of a complex and individual construction task like this. The options for action are many and can be determined only after a more in-depth analysis of the causes that led to the problem. Linking to a company specializing in one type of activity most often leads to the implementation of its system, without a guarantee for an optimal solution. In general and conditionally according to the specific site, the following steps can be taken:

First step - a study to select a qualified specialist to assess the situation. This step sets the direction for further action and at the same time can save a lot of money, time and unnecessary activities. Consultation is the lowest cost of eliminating such a problem.

Second step - to give a definite answer about the level, the nature of the groundwater and the possibilities for their reduction. If necessary, to inspect the structural elements affected by moisture to determine their current state.

Third step - to apply simple and easy measures to deal with the problem. Such are diagnostics of the internal plumbing installation, replacement and discharge of the gutters from the roof and others.

Fourth step -in the absence or insufficient result of the above activities, proceed to the diagnosis of the external plumbing installation of the building, provided that the leak is year-round.

Fifth step - for each specific site, is the implementation of one or more measures such as a drainage system with or without a hydrophore, partial replacement of an external HI, injection of resins and solutions directly into the structure.

Waterproofing injections

The injection method is particularly effective in the case of local moisture or leakage in wall or floor elements and especially in the connection between them. Its main advantages are the created water tightness in the whole section of the element, the protection of the reinforcement from corrosion, the fast execution without the need for breaking, deformability after connection. Polyurethane resins have an extremely long service life - as long as the life of the building. Another advantage of polyurethane is that it does not harm the environment and humans. The disadvantages are the complexity of the operations and the need for special pumps. This technology is applicable to concretes with sufficient mechanical properties. Continuous control and participation by specialists in the field is mandatory.

Additional drainage system

The construction of an additional drainage system, reducing the water level under the foundations of the building, is also an often applied, efficient solution, but it hides its risks. In many cases, when the drainage is completed without the obligatory intervention of a geologist, it does not function well enough, after some time it becomes clogged or causes the collapse of earth layers due to hydraulic destruction of the soil.

The drainage system locally lowers the groundwater level under the building:

When the level of the drainage system is below that of the street sewerage network, the additional installation of a hydrophore is required.

The drainage system is a very suitable, but not universal, approach. Its higher price can be justified by solving a complex of problems related to the high groundwater around the building.

Waterproofing of underground parking lots, garages and basements

Waterproofing leaky or damp walls and joints of underground parts of the building is a large venture. It is possible to apply different techniques in different parts of the building. The ultimate goal is to protect the building and significantly reduce the humidity in its premises.

These elements imply the use of more economical materials and technologies. In most cases, gradual treatment of leaks is applied. The first stage is sealing the active leaks in cracks and joints between the elements. This can be done by coating with fast setting cements or injection with polyurethane polymers. After a reliable stop of the water, a deeply penetrating impregnating agent is applied on the concrete surface. The third stage is the application of greased, high-tech cement-based plaster.

Sometimes the solution turns out to be simple and does not require expensive interventions. However, untimely intervention on problems with leaks and moisture inevitably leads to property damage, endangering the safety of occupants, the need for complex and expensive repairs to the structure and elevator system, reducing the life of the building and aesthetic defects.

Our team performs on-site consultations, as well as the implementation of activities to eliminate active leaks and moisture.
Do not hesitate to contact us! 
Автор:Dr. Eng. Teodor Todorov


In the central urban areas, there are still many buildings with wooden floors. Their attractive location dictates a constant trend of change in their purpose. Their transformation from residential buildings into offices and public places is associated with increased requirements for the buildings themselves. The increased load, the need for sound insulation, thermal insulation and fire protection require changes to the existing wooden joists. In this article, special attention will be paid to the constructive point of view in accordance with modern understandings of structural safety and measures for its provision.

Behavior of the joist in an earthquake

The main feature that a number of modern scientific studies focus on is the vulnerability of buildings with wooden beams to earthquakes. The old masonry structures, whose storey levels are solved with wooden joists, show extremely unfavorable behavior and are the predominant part of the severely affected or completely destroyed buildings in past earthquakes.

After a thorough structural analysis of existing historic buildings, the engineers came to the conclusion that the joist is the weakest link in this type of construction. The classic, well-executed and preserved joist also does not meet the basic structural requirements formed after the analysis of such damage. The main disadvantage of this type of elements is the inability to properly redistribute the horizontal earthquake forces to the vertical elements - columns, walls. Simply put, the "soft" joists do not allow the transmission of forces to the walls that are designed to absorb them. As a result, there is an overload of individual vertical elements until their destruction.
Another serious structural problem with wooden joists is that, unlike reinforced concrete slabs, it does not provide transverse space stability of the load-bearing masonry walls. Unwanted behaviors that occur, most often outside the plane of the walls, lead to their premature destruction.

Despite their significantly higher number of storeys and weight, modern buildings, filled with reinforced concrete skeleton and reinforced concrete slabs, prove their reliability in any major earthquake. Under the same influences, different constructive systems show radically different behavior. Some remain literally unaffected, while those with wooden beams suffer fatal damage.

Since the buildings in question with trimmers obviously have a deficit to absorb earthquake impacts, several logical questions arise.

Can this be compensated?
What are the main directions in which engineering thought should be focused in order to achieve acceptable levels of security?
At the same time, how to preserve the original vision and harmony, especially in cultural monuments?

The task is further complicated by the financial factor and the variety of masonry and joists. Undoubtedly, for each project an individual solution must be sought according to the specifics. Several possible variants are shown in the illustrations below, and their application must take into account the desired results and the initial parameters of the structure. Thus, for example, it is not reasonable to apply a concrete fill if the walls of the building are not able to absorb greater transverse forces due to the increased own weight of the slab.

The decision to select an amplification system must be motivated by the results of a thorough on-site analysis. There are many cases in practice in which the performed reinforcing measures have a rather negative overall effect on the structure.

Important moments when repairing the joists

One classic solution, widely used in our practice, is concrete filling combined with reinforcing mesh and anchoring elements.

Such a solution increases the qualities of the floor construction, but adds extra weight on the vertical elements. Detailing the connections between the old structure and the reinforced concrete fill is a key point that in most cases incompetent contractors miss.
During construction, the monolithic construction of the existing beams in the masonry was carried out only with masonry mortar. The created connection is fragile and transmits horizontal forces only in one direction. In order to increase the bearing capacity of the joist in all directions, its planar hardening is necessary. Such systems consist of additional fasteners transmitting forces between the individual elements of the joist and leading them securely to the walls intended for earthquake absorption. Designing such a system is a delicate task. The omission of some moments in the solution and leads to a significant reduction in the efficiency of the repair.

Thermal insulation, fire protection

In the planned repair measures it is good to consider the issue of reducing the weight of the floor structure. Replacing the filling between the beams of the joists with modern thermal insulation and sound insulation materials is a cost-effective and logical solution. Given the location of the new thermal insulation, it is desirable that it be made of non-combustible and non-toxic material such as glass or mineral wool.

Last but not least, during the constructive repair of the joist, it is important to take modern measures for its fire safety. The Bulgarian norms regulating the fire protection of wooden structures are Eurocode 5 - Part 1.2: Design of structures against fire. One successfully applied method for passive fire safety of wooden elements is cement or gypsum plaster with a thickness of 20-30 mm, laid on a netting.

You can contact us for assistance in diagnosing the building, preparing a project for fortification activities, as well as their subsequent implementation.  

Do not hesitate to contact us!  

Author: Dr. Eng. Teodor Todorov


The terms soft, cramped or weak floor are used in multi-storey buildings when one or more floors have a significantly smaller capacity to absorb earthquake impacts. A floor can be classified as "weak" when, figuratively speaking, its carrying capacity is below 70% of the carrying capacity of the floor above it or 80% of the average carrying capacity of the upper three floors. The presence of a weak floor is an extremely dangerous and common phenomenon in Bulgaria. Observed in the functional need for large openings for doors, car entrances or large windows, in place of antiseismic washers, especially along the facades of buildings.

Consequences of having a weak floor

Such openings may have been provided during the design of the building or may have been identified later. Modern scientific studies unequivocally prove that killing a door or window opening in brick buildings, without a reinforced concrete skeleton, reduces the load-bearing capacity of the wall to 70 ÷ 80%. In those with well-performed columns, beams and slabs, the load-bearing capacity varies from 50 to 70%.

The extreme seriousness of the problem is also proved by the results after the processing of information breaking the causes of severe damage in earthquakes. The main share of the severely damaged or completely destroyed buildings is due to the presence of a weak floor in the affected structures. An example is the Loma Prieta earthquake with a magnitude of 6.9, which in 1989 caused the destruction and severe damage to more than 160,000 homes. The subsequent report shows that nearly half of the buildings were damaged precisely because of the presence of a weak floor. The real danger and the great damage caused in the past have become the cause of government policies aimed at securing buildings suffering from this structural defect.

ATTENTION! The video contains disturbing footage!

Unfortunately, the weakening of load-bearing walls in the ground floors of buildings is an extremely dangerous but common practice in our country. The condominiums along the central city streets have been literally uprooted on their ground floors, in order to separate commercial areas with large entrances and windows. Even more dangerous are the reconstructions removing walls of two floors, as well as internal walls of the premises.
Mass reconstructions are justified only by a constructive opinion from a design engineer. He categorizes the affected wall as non-bearing, which avoids the need for mandatory antiseismic reinforcement of the hole. Apparently, the state services often neglect and blindly trust the "expert" opinion of the designer, which allows the implementation of real threats to the security of the building.

What are the reasons for not carrying out the mandatory reinforcement of the openings?
As in many other areas, in the first place, the neglect of a critical problem like this is dictated by the relatively high costs of strengthening the openings. Owners and tenants are willing to sacrifice the security of the entire building and its occupants, hoping for weaker earthquakes in the coming years. The prices for framing of openings start from 1200 ÷ 1500 BGN, as the quality execution and the dimensions of the new opening can increase the price several times to about 5000 ÷ 6000 BGN.


Another reason is the relatively slow procedure for legalization of reconstruction affecting the load-bearing elements of the building. For the new buildings it is necessary to obtain a constructive opinion, design visa, projects and permits, supervision and a licensed contractor. For older buildings, the procedure is longer and includes inspection, certification of the building and other activities. All these stages are mandatory and aim at a reliable end result ensuring the security of the building and its occupants.

The technological nature of the reinforcement is also an important factor, as sometimes the initial conditions significantly complicate the project. The presence of joists, thin slabs or weak masonry and foundations require the implementation of more complex and general fortifications providing the entire building.

Some design solutions include elements occupying part of the dimensions of the opening. Such obstacles may also impede the proper implementation of the project. Retail owners are looking for maximum light space and are often willing to risk the security of the building to get it.

Which buildings are most at risk?

Research indicates that the most affected by the phenomenon of "soft floor" buildings with brick construction, without the presence of reinforced concrete columns and beams. Buildings with a reinforced concrete skeleton but without reinforced concrete washers are also severely affected by the construction of new openings.

In general, constructions in which such alterations are made on the facade walls are more dangerous than those in which the removal took place inside the building. Prefabricated buildings also often fall victim to this type of renovation. In them, almost all interior walls perform a load-bearing function, and the facade mostly assists. Last but not least, higher storeys are associated with higher loads. As the height increases, the structures become significantly more vulnerable to earthquakes.

Why is it mandatory?

Recent decades have seen great progress in understanding the behavior of old structures in earthquakes. The global survey of buildings destroyed by earthquakes has clarified many issues and radically changed perceptions of anti-seismic construction of buildings. It turned out that the design models used before the end of the 20th century were generally misconceptions. The presence of a weak floor in the structures has been severely neglected, and in our practice this significant problem continues to be not considered with sufficient attention. Modern knowledge defines the buildings built before the 90s of the last century as not very reliable in an earthquake. Their additional weight loss by up to 80% in highly seismic areas such as the Sofia plain is an extremely risky and irresponsible process, which unfortunately continues to this day.

You can contact us for assistance in diagnosing the building, preparing a project for fortification activities, as well as their subsequent implementation.  

Do not hesitate to contact us!  

Author:Dr. Eng. Teodor Todorov


What is the capillary rise of water in the building?


The process of capillary rise is expressed in the rise of water through the walls of the basement or other underground structural elements, causing moisture in the premises. Depending on the composition, connectivity and size of the pores in the material, water rises more or less, causing moisture by capillarity.
Materials such as brick, wood and poorly compacted concrete have a porous structure that allows moisture to rise in height.

The chemical composition of moisture contains more or less mineral salts, which are deposited on the surface of the wall during its evaporation. A clear sign of this process are changes in the color of the wall, most often lightening.

If you notice wet spots on the walls near the floor, most likely your home is affected by capillarity. The height that wet spots can reach depends on factors such as:


- groundwater level and its seasonality

- materials used in construction

- temperature, humidity and ventilation of the premises

- conditions for the transfer of moisture from the wall to the room

- presence of salts and their crystallization on the wall surface

- previous interventions aimed at limiting the humidity in the premises


Capillary moisture occurs in walls that are not well insulated in the base or where there is damage, or not well executed waterproofing. High groundwater in many regions is year-round, which creates conditions for intensive development of mold, mildew, accompanying unpleasant odors and poor appearance of the premises.

What are the risks if we do not solve the moisture problem?

Increased humidity is expressed in wet spots, swelling of the plaster, separation of pieces of it, change in the color of the walls, the formation of mold, mildew and odor, rot of flooring and furniture.
In addition to the purely aesthetic negatives, the increased humidity in the walls and rooms poses serious risks to the health of their occupants. Constant exposure to spores from molds and toxic substances released during metabolism, as well as high humidity cause infectious diseases, allergies, asthma and even cancer.
Another much overlooked effect of long exposure to capillary moisture in the building is the weakening of the materials from which it is built. Corrosion and reduced mechanical properties are not observed not only in steel and wood elements, but also in those of concrete and brick.

When water evaporates on the surface and inside the wall, salt deposits are formed. The process of passing the capillary moisture through the structure is accompanied by the extraction of chemical elements from the composition of the building materials, which significantly reduces their mechanical properties. Clogging the surface pores with salts creates additional hydrostatic pressure and separates the plaster from the walls. Also, over time, there is an increase in the level of wetting in the wall. High humidity significantly increases the thermal conductivity of materials, which increases the cost of heating and cooling.


Neglected over time, such processes significantly reduce the quality of the building and its life.

What are the possible solutions?

Improving ventilation

Artificial ventilation of the premises and the installation of dehumidifiers in some cases solve the problem by drying the surface layer of the affected areas, which stops the development of mold and mildew. In the case of small amounts of moisture passing from the soil to the underground parts of the building or moisture generated during the operation of the premises themselves (laundry, sanitary facilities, etc.), it can be said that this approach is quite successful and most cost-effective. . But not universal! When it comes to intensive penetration of moisture from groundwater, the effect of air drying is enhanced water filtration and acceleration of the dangerous processes of chemical corrosion in materials.

Treatment of capillaries in the material


The sealing of the capillaries is done by various technologies, mostly according to the material from which the wall is made and its condition immediately before the repair. Basically, the methods differ depending on the pressure with which the irrigation with mineralizing liquid is performed. Highly porous materials such as clay masonry can be treated without pressure, while relatively thicker concretes require forced pressure. It is necessary to achieve a watertight internal barrier throughout the cross section of the element. Polymerization products use different chemical elements, but the general principle is to reduce the number and size of capillary pores. The newly formed chemical compounds have a strong hydrophobic effect.

Execution of waterproof plaster / screed / membrane


The composition and properties of some materials do not allow the application of the above method. When it comes to underground parts of the building, access from the outside of the affected areas is also often very difficult. Then there is the possibility of sealing moisture in the wall by building a watertight barrier on the inside of the base of bitumen, cement mortar and others. Such a solution is most often offered by masters and manufacturers of waterproofing materials.


Significant disadvantages of such an approach are the short-term effect of most systems, as well as the concealment of the problem without it being actually solved. The development of mold and mildew continues, and the construction of the building inevitably weakens over time. The repeated implementation of the waterproofing and the accompanying finishing costs seriously call into question the profitability of these repairs.

Drainage systems

Building a drainage system is a more expensive solution, but it also has its undeniable advantages. A well-executed drainage system could function smoothly for decades, fully protecting the building and its internal parts from the action of groundwater. The sanitary and hygienic conditions, as well as the thermal insulation indicators of the underground part of the walls are significantly increased. In certain cases, the drainages can also be used for partial stabilization of the soil when the foundations sink. The depth of laying the drainage pipes depends on the external dimensions of the building and the soil characteristics.


 Unfortunately, in search of the lowest price, owners often come across contractors offering compromise solutions and ultimately need to rebuild a new drain. Saving on a geotextile membrane, shallow laying of drainage pipes and the implementation of a backfill with ordinary soil doom the enterprise to failure. Although in rare cases, the implementation of partial drainage on one or two of the facades can lead to uneven subsidence and structural problems for the house. The lack of geotextile and the backfilling of the backfill with uncompacted soil cause movements in the soil, respectively in the foundations of the nearby buildings. Within a few years after laying the drainage, the foundations yield, forming oblique cracks in the walls.


Another important point in the implementation of larger drainage activities is the performance of hydrogeological research. The information from it serves for reliable design of the drainage system with a minimum volume of excavation works. The results of the geological report can also be used in future fortification activities.

Ultimately, the choice of solution is individual for each site. The competent determination of the amount of damages, their specifics, the technical possibilities for manipulations on the materials, the proposed repair options, the purpose of the premises and the investor's desire to maintain the building are the key factors. They determine to what extent and for what period of time each construction problem will be solved.

You can contact us to prepare and implement an optimal solution according to your specific case.

Author: Dr. Eng. Teodor Todorov



In the past 2016 228,586 new property owners are registered with the Registry Agency. However, the number of deals with new homes is only a small part of this impressive figure. For most newcomers, among other indicators determining the profitability of the purchase, with particular weight in choosing a home should consider the remaining life of the building. This concept is relative and is a combination of many factors. The most significant of them are structural security of the building, moral and physical depreciation, maintenance costs, opportunities for reconstruction and increase of the useful built-up area.

Functional reconstructions

The first criterion for determining the residual life of a structure is its functionality and the possibilities for changing its purpose. In recent years, the economic interests of owners and investors have created a wave of restructuring. Modern business needs turn semi-underground premises into shops, former factories - into shared workspaces, apartments - into restaurants and entertainment. Thus, a large number of premises and entire buildings with reduced or completely exhausted resources, according to their original purpose, are put back into operation.

This sustainable trend is possible thanks to the application of original architectural solutions, significantly increasing the residual life for, at first glance, completely worn out physically and morally buildings and premises. Particularly flexible and modern, it is found on both large and small scales. Allowing many small businesses to save on high rents or capital investments for new construction, while realizing environmental savings through full use of the already built building stock.

Constructive security

As a mandatory condition for this to happen is the most important indicator determining the residual life of a structure, namely - its structural safety. It is quite logical that the global trend of this security is constantly increasing. Thanks to the rapid development and application of new technologies for design and implementation, the increasing requirements for the seismic safety of buildings, the intensified international exchange of knowledge and normative documents are constantly increasing this indicator. These factors also guarantee a longer and trouble-free life of the structure. In addition to increased security, the development of construction technologies allows the realization of bolder. architectural solutions even in earthquake-prone areas, as well as increasing the number of storeys of buildings.

Quality of construction

The widespread claim of higher quality construction before the 90s of the last century is greatly exaggerated. The main argument in support of this thesis is the inability of most of the old buildings to meet the modern, mandatory for new buildings, design requirements. Inspections of such old buildings very often reveal serious discrepancies between the norms in force at that time and the actual implementation. There are many buildings that were built without the necessary construction documentation, but subsequently legalized only on the basis of architectural photography. The time check often covers only the quality of the waterproofing of the foundation, the finishing works, the laying of the foundation and the functionality of the premises and the adjacent areas around the building. Most of the old building stock could actually exist for tens and hundreds of years without the need for structural repairs, but not only with quality funding, lack of seismic impacts and bends. After a subsequent increase in earthquakes, occurring on the territory of Bulgaria in the last 100 years, are completely or partially destroyed cities, tens of thousands of neighboring buildings and not a small number of human casualties.

                                          The Catholic Hospital in Plovdiv after the Chirpan earthquake

Despite the better modern norms and methods of design, both in the past and today there are no examples of practice with serious violations. Most often they are in the implementation phase of projects. The most common defects that reduce the life and safety of a building structure are:

• poorly vibrated concrete, insufficient coverage of the reinforcement

 • insufficient reinforcement and sagging of horizontal elements

• excessive reinforcement of horizontal elements

• incorrect decomposition of the reinforcement during installation

• displacement of the reinforcing skeleton during concreting

• low quality of the used materials

• presence of high humidity in bearing elements

• uneven subsidence of the foundations due to poor foundation or water filtration

Statistics on the causes of accidents in construction

Due to the great variety and different significance of these defects on the security of the building, it is not possible to give an unambiguous answer to the question "how long is the life of a given type of construction". It is more important to pay attention to and analyze to what extent these defects are removable and whether it is profitable.

In many cases, the defects are relatively easy to eliminate with small investments. For example, in case of insufficient reinforcement, composite systems could be applied, the application of which takes hours and significantly increases the security of the whole structure.

Some repair works, such as the addition of underground waterproofing, not only improve the conditions in which the structure is located, but also increase the quality of the living environment. The reduced humidity guarantees better thermal insulation properties of the partition elements, removes the presence of mold and mildew, improves the subjective feeling of clean air.

In other cases, achieving acceptable levels of security and increasing the life of the building are financially unprofitable. Especially when it comes to small buildings in developed urban areas, where the structural indicators allow larger building parameters and there is interest from private investors.

Moral aging

The obsolescence of premises and buildings must also be taken into account in a long-term investment, such as real estate.
For example, prefabricated blocks with a constructive life of over 100 years, such as more than 20% of homes in the country, do not tolerate special options for reconstruction. In foreign practice, projects are implemented that completely change their appearance, energy efficiency and market value. And the premises and buildings must also be taken into account in a long-term investment, such as real estate.

In the most general case, the design life of investments in construction and equipment varies within the following limits:

• improvements of the surrounding space - 20 years.
• life of the buildings - 25 ÷ 60 years.
• their furniture and equipment - 2 ÷ 15 years.

After a certain period of time, the funds needed to repair and renovate the building stock increase dramatically and the investment becomes unprofitable.

You can contact us for assistance in choosing a new, safer home. Making the right, informed decision when buying saves big costs for owners in the future. 

Do not hesitate to contact us!

Author: Dr. Eng. Teodor Todorov


Unfortunately, earthquakes are a relatively common phenomenon, especially for areas with high seismicity such as Bulgaria and the region. Recent events in Albania and Croatia have confirmed this. Although not very strong, they caused great material damage, destroyed buildings and even casualties. In the Bulgarian team sent to Albania Dr. Eng. Teodor Todorov from "Renovate", author of the article, also took part in assessing the damage from the earthquake. The main part of the presented photo material is a personal archive from the cities of Tirana and Duras.

What distinguishes earthquakes from other natural disasters is their sudden, unpredictable nature.

The unexpected and destructive nature of earthquakes puts us in a position of entirely preventive measures. Prevention measures can be of two main types. The first concerns the security of the building. The second, the knowledge with which we will meet the moment of the earthquake. And while structural reinforcement is an expensive and complex process, knowledge of buildings and the hazards associated with them is significantly more accessible and just as important.

Read more: Which is the most dangerous for a building

What are the preventive measures we need to take?

First, it is important to have a clear awareness that the occurrence of stronger earthquakes in Bulgaria is not a matter of "whether", but rather of "when". There have been such earthquakes and there will certainly be again. The consequences can be very severe, even catastrophic. That is why it is important to enter such a future situation as prepared as possible.

  • Choice of neighborhood and building to live in

Presumably, the newer a building, the safer it is. Of course, there are many exceptions. Mostly as a result of unscrupulous builders. However, scientific and technological progress also has a positive effect on building construction. It is high time that the myths of old and quality construction remain in the past.

Read more: New or old construction


The main disadvantage of the newest buildings built in the last 20 years is the weak strengthening of the partition walls. Combined with the lack of free evacuation space between buildings in the new neighborhoods, falling facades and windows became the main danger for people who managed to leave the buildings. The experience of Albania, as well as other countries, shows the effect of well-designed and implemented structural systems, but poorly reinforced partition walls.

An additional reference point when choosing a home could be the geological map of Sofia or another city in the country. These maps indicate the approximate locations of the faults with the expected greatest damage to buildings.

Preventive preparation

In addition to knowing how to react in such a situation, it is necessary to organize a few simple but vital things in advance.
Reliable attachment to the walls of all heavier objects such as wardrobes, refrigerator, showcases. Also, each prepared household must collect in advance all important documents, electronic media and spare keys for cars and real estate in a separate box. For some people, the box may also contain stocks of vital medicines such as insulin and inhalers. Important documents are, for example, deeds of ownership, passports, health books and cards, company documents and other papers. The crisis box must be left in an easily accessible place, ready to be picked up within seconds before the evacuation.

During the evacuation

The reaction time is extremely short. If you feel that you are not able to leave the building within ten seconds, you better not try. It is mandatory to have previously identified the safest possible place in the home. And no - it's not under the door frame! Even less on the balcony! Stay away from windows, cabinets, glass cabinets and power panels. Proximity to the facade walls should also be avoided at all costs. Relatively safe places are close to the load-bearing washers of the building, under reinforced concrete girders and near the center of the building.

In old buildings, the attic space and the top floor are the most vulnerable places. If you are there, move to a lower floor immediately. The consultation with a specialist she could guide you to where the safest places are, specifically for your home. Standing under solid tables and desks can also protect you from falling plasters and cabinets. Which is not small. The correct waiting position is to squeeze the ball with a hand protecting the head and nape. With the other hand, hold the moving table or desk.

It's good to always have easy-to-wear shoes on hand. Broken glass is especially dangerous in such situations. If it's cold, be sure to grab warm clothes or blankets. If you stay longer in the building, try covering your nose and mouth with a thick cloth. Strong earthquakes inevitably cause the fall of plasters and walls, generating a lot of dust. Physical damage from debris and suffocation are the main factors causing fatalities for residents.

Nearly 10% of earthquake victims were caused by subsequent fires. If you feel a primary quake, it is advisable to stop the gas supply and turn off the main fuse in the apartment. This takes a few seconds, but can be crucial to your property and the lives of others in the building.

Critical points during the evacuation are the stairs and exits of the building. Needless to say, the use of an elevator is highly undesirable. However, in an earthquake, the stairs also become places with an increased risk of slipping and injury from cutting objects. Fallen plaster and broken glass are a prerequisite for unexpected slips in the commotion during evacuation. Running on them, especially in the dark, carries a huge risk of severe and even fatal injuries. If possible, hold on to the guardrails throughout the descent to the exit. Gathering many people further complicates the situation. It is important to avoid creating panic as much as possible!
This is what the stairs of new buildings look like after the 2019 earthquake in Albania.


The photos clearly show the many pieces of plaster on the floor, which make it extremely slippery. There are also broken windows in the areas around the windows. Large amounts of dust greatly reduce visibility during evacuation. In such a situation, do not panic, do not rush too much and be careful how you step!

The exits of the buildings, in turn, also turn out to be high-risk places. It is advisable to cover your head with your hand when leaving the building. This can protect you at least in part from falling smaller objects and pieces of glass. It is important to move away as quickly as possible from the surrounding buildings and power lines. The photo shows the pouring of several partition walls at the exit on the side of the building.

Sometimes a relatively light tremor is able to separate poorly attached large, facade elements.

Actions after successful evacuation and stopping of the first earthquake

Once you have successfully left the building, check for injuries yourself and the people around you. High adrenaline greatly dulls the pain. Cuts may not be felt in the first few minutes and cause severe blood loss. Give first aid or help if there are victims.

Unfortunately, there is no way to predict whether the perceived earthquake will be followed by other, stronger ones. Even seismologists can only make uncertain suggestions. Before returning the occupants to the building, however, it is mandatory to make a few vital, subjective observations. The first is a subjective assessment by the owners of the condition of the building. The presence of cracks, sloping walls, jammed doors and windows is a clear sign of serious damage.

The building suffered damage that most likely made it significantly more vulnerable to a aftershock. There are many cases in which subsequent weaker earthquakes destroy buildings that survived the main quake. If the building has an underground floor, it must also be at least subjectively inspected. Beware of damage to load-bearing elements such as columns and walls. The underground and ground floors are the busiest in the construction. Bottom-up destruction is extremely dangerous and sudden.

In the event of any signs of damage, the building must not be inhabited before being inspected by a specialist design engineer. 

The second important thing that must be paid special attention to is the condition of the buildings in the immediate vicinity. Destruction in them can cause a domino effect. Contact between buildings causes huge, sometimes even fatal damage to structures.

The third element of the minimum measures that can be taken by the occupants is the central shutdown of the gas supply and the electricity in the building. If you notice cracks on the facade and inside the premises, it is possible that these displacements have caused damage to the gasification and electrical installations. Gas leaks can be small or in places where you will not immediately smell. Over time, however, the concentration of gas in the room may become sufficient for ignition and fire. Contact specialists as soon as possible before restoring gas supply. Leave windows open for ventilation.

In case of already established damage to the building, the next mandatory step is inspection and consultation with a construction engineer. He must visit the building on site and make a detailed inspection of the damage. Its initial assessment will clarify whether the building is habitable and whether measures are needed for its subsequent inspection and strengthening.

If you still stay in the building and you do not have the opportunity to leave it, keep your composure and save your energy. If you have access to your phone, turn off internet data and GPS tracking. Save battery and use the phone only when necessary!

You can contact us for assistance if you need specific information related to your building. 
Do not hesitate to contact us!  
Author: Dr. Eng. Teodor Todorov


One of the first questions that arises with our desire to buy a home is new or old construction. What are their advantages and disadvantages and what to look for when choosing.
The long-term and scale of the investment, the potential problems after the choice, as well as the possibility of large unforeseen costs in such an endeavor, requires serious research and patience on the part of the prospective buyer. Early warning decisions to buy a home can bring serious headaches instead of the joy of a new home. Unfortunately, there is no single answer to the dilemma of new or old construction. However, if we assume that there is a better solution for each specific buyer, in this article we will outline vital elements when choosing a new home.

Surroundings and infrastructure

New construction

Developing the surrounding spaces around the building takes time. If you are looking to buy an apartment in a new neighborhood, pay attention to the percentage of green space. On a large scale, they are extremely scarce and are more likely to turn into car parks or new buildings than into tree gardens and benches. The lack of outdoor landscaping and free spaces should be taken into account in families with children or when they are included in future plans. Infrastructure such as public transport, road surface, various shops, playgrounds, kindergartens, schools are also significantly less developed or completely missing. Areas such as "Monastery Meadows" become "Mission Impossible" for parking and walking. Mass redevelopment significantly deteriorates the quality of life of the environment.

Old construction

One of the main reasons for the old construction is precisely the well-developed infrastructure and landscaping in the inter-block spaces. The environment is almost always significantly friendlier and offers an alternative to leisure. In some of the neighborhoods the structural indicators remain unchanged, which in practice means that the regulation plan does not allow for larger-scale construction than the existing one. The open spaces between the buildings undoubtedly increase the comfort of their occupants.

What we acquire

Until 1991, the area of ​​the apartment by notary deed included the area of ​​all rooms, partition walls and ¼ of balconies, loggias, terraces. After the adoption of the "Ordinance for determining the basic market prices of real estate", to the area of ​​the apartments are added the adjacent common areas, attics and basements to the property, as well as 100% of the area of ​​the terraces. Thus, an old apartment of 80 sq.m. for example, it could reach 96 square meters if it is recalculated according to the new norms. This fact must be taken into account when comparing properties whose prices are set per square meter.

Parking spaces

New construction

According to Ordinance № 2 of June 29, 2004 for planning and design of communication and transport systems in urban areas, depending on the functional purpose of the site, a certain number of parking spaces for vehicles is provided. Some builders find loopholes by announcing a different status of the premises, which reduces the number of mandatory places according to the ordinance. But even correctly applied, the law raises two main questions. The first is that the parking spaces in question are sold as separate property. None of the new owners is obliged to buy a parking space or a garage, as the price varies from 10-15 000E. But let's say that these parking lots will be filled with time anyway and will be used 100%. The more serious question is, is their normative number determined according to the current reality? One place per apartment and one place for 100sq.m. offices. And after 10 years? In 20 years? Of course, there are business buildings and gated complexes, which undoubtedly offer more comfort in this regard.


Old construction

Here the problem with parking is strictly individual. Decisive factors are the location, dimensions of the surrounding road infrastructure, the status and age of the majority of the inhabitants. There are still areas where parking spaces are easy to find. Where this is not possible, parking on lawns has become a common sight. Municipal institutions are neglecting the problem by remaining indifferent, at least for now. In addition to the purely aesthetic aspect, parking cars in lawns leads to significant pollution of the road surface and subsequent dusting of the air with fine particles.

Construction of buildings


The presumptions in the development of the design are entirely in favor of the improvements. In recent years, the safety of structures has greatly increased, more economical and appropriate solutions have appeared, new materials and technologies for implementation are constantly being introduced. Back in time, the 1957 earthquake design regulations. does not consider buildings up to 11 m high (4 floors). Moreover, buildings designed according to the norms and international rules and design criteria in force at the time suffered significant damage and destruction during earthquake impacts. This caused in the period 1970-1975 to form a completely new, global concept for earthquake design. Although in 1978, temporary regulations for seismic insurance were prepared in Bulgaria, it was not adopted. The country remained without modern regulations until the 1987 earthquake in the town of Strazhitsa.


The next significant improvements in the legislation are in 2007. and 2012 - Eurocode 8 for seismic impacts. The improvements in the regulations in question increase the requirements for the design of the structures and the quality of the materials used. For some buildings, this also leads to an increase in the amount of concrete and reinforcement, which increases the cost of construction.
Undoubtedly, the design has made significant progress over the years, providing greater levels of security for the occupants. In 2016 the book came out "Seismic safety of large-panel structures. Myth or reality." . In it, Assoc. Prof. Dr. Eng. Atanas Nikolov and Ch. Assistant Engineer Radoslav Orlinov from UACEG presented an in-depth study on the topic. The book discusses the importance of the spatial solution of the building on its seismic resistance. The principles are also valid in the initial assessment of existing masonry structures. This means that there can be a huge difference between buildings built at the same time, with the same materials. This difference should be assessed by a specialist and taken into account as the main criterion when choosing a "new" home.

Inserted materials

Technologies for the production, transport and storage of building materials are also evolving over time. Some materials are partially or completely replaced by others. The transition from masonry load-bearing walls and joists to reinforced concrete structures occurs within 40-50 years. The difference in seismic resistance between generations of buildings is incomparable. In the last 30 years. the execution of reinforced concrete structures marks a significant leap in quality.

За привържениците на тезата „старото е по-качествено” ще отбележим няколко ключови аспекта повишили драстично надеждността на стоманобетонните конструкции през последните 20-30г.

In the past, concrete was transported by dump trucks. Vibrations on the road lead to stratification of the concrete (separation of gravel, sand and cement mortar). The result is an inhomogeneous concrete mix with low ductility and reduced strength.


Transportation of concrete with mixers and its laying by concrete pumps is faster, cleaner and without delamination.


Modern formwork systems do not allow deformation of the elements during concreting and seepage of water from the concrete.



The vibration (compaction) of the concrete mixture plays a key role in its strength and performance, as well as on the watertightness of the elements. In the past, due to ignorance or lack of appropriate equipment, not much attention has been paid to this problem. Today, however, every reputable builder makes the necessary efforts for the proper laying and compaction of concrete.


The quantity and quality of the reinforcement used is also constantly improving. According to Eurocode, modern reinforcing bars are only ribbed, have higher adhesion to concrete and better performance.


In the past, bars of smooth reinforcing steel were widely used, over long distances, with small diameters and poor adhesion to concrete.

Quality of execution

Implementation errors are the cause of over 50% of construction accidents. Sometimes seemingly small details can threaten the security of the building. At the end of the 20th century in Bulgaria there was a period of rapid construction, poor quality control and a large number of illegal buildings. Some of them were subsequently legalized despite the discrepancies or received the status of tolerance, without having the necessary design qualities. After the changes in 1997, control over construction activities began to slowly strengthen, increasing the quality of design and execution. A number of normative changes have been introduced aimed at better synchronization between the participants in the construction process. This continuous improvement process undoubtedly adds value to newer buildings, which should be reflected in the choice of purchase. Unfortunately, the finishing works lag behind the trends imposed on the structures and do not always offer adequate quality.
Of course, there are still builders who manage to save on the quality of construction. However, it can be argued that increased control over construction has significantly reduced their number.

So, in the end, the prospective buyer must make a balanced choice between the price per square meter, communication, surrounding infrastructure, parking spaces, a sense of space and cleanliness and last but not least - the security of the building. The different needs of each buyer make the answer to the question "new or old construction?" strictly individual. We are not saying that this choice is easy, but given the size and duration of the investment, it is appropriate to take the time to research and make the right decision.

You can contact us for assistance in choosing a new, safer home. Making the right, informed decision when buying saves big costs for owners in the future. 
Do not hesitate to contact us!  
Author: Dr. Eng. Teodor Todorov


The development of terraces in prefabricated homes is a common practice in our country. Joining a terrace to a kitchen in a panel block is probably the most common example of reconstruction in Bulgaria. Along with the glazing and additional partitioning of the balconies, many of the owners decided to remove some of the facade panels on their own. What are the risks of such inclusion?

What is the function of the window sill on the balcony

In order to improve the ergonomics of the premises, it is common practice to partially or completely remove the window sills. The pretext for such a reconstruction is that they have no bearing function. However, as can be seen from the diagram below, these elements are the closing link in the connection between the floor and wall panels in large-panel residential buildings.

In the nomenclature of large-panel residential buildings there are also those whose connection between the balcony and the facade panels is carried out by means of butt welding. There are not isolated cases in which the welds in the panel blocks corrode to such an extent that the balconies sag or collapse. For now, these cases are rather episodic, but over time and the aging of the blocks, they will inevitably become more frequent.

Signs of a problem with the balcony and aggravating factors

The first signs of sagging of the balcony and potential danger can be seen around the connections of the railing with the facade wall and around the inner edge of the balcony bay window.

Освен намаляването носимоспособноста на балкона, след избиването на подпрозоречната стена, с приобщаването собствениците често  увеличават натоварването действащо върху него. Добавянето на теракот или гранитогрес, преградна зидария, остъкляване, топлоизолация, готварски уреди, принадлежности и шкафове се равнява на маса от 1000-1500кг. Тези допълнителни над 300кг/м2 не са заложени никъде в изчисленията по време на проектирането.

What can be done

A sensible solution is to build an inexpensive additional support for the balcony. Unfortunately, the optimal location of such a preference is on its underside. Thus, part of the weight can be successfully transferred on the lightly loaded facade walls in the panel blocks. Re-support is also possible with other structural systems, with some conditions. The aim is to significantly facilitate the work of the console terrace to ensure security for the occupants. Particular attention in this type of intervention should be paid to the anchoring elements.

Подпиране на провиснал балкон

You can contact us for assistance in diagnosing the building, preparing a project for fortification activities, as well as their subsequent implementation.  

Do not hesitate to contact us!  

Author: Dr. Eng. Teodor Todorov



The sinking of the old buildings is a common phenomenon throughout Bulgaria. In addition to the many cosmetic damages that the processes of sinking of the foundations cause, they are a good cause for concern among the inhabitants. Before taking any action to resolve the issue, the following questions must be answered on a case-by-case basis:

Is the house safe for the occupants at the moment?
Is the facade safe for passing cars and pedestrians?
What causes the subsidence / sinking in question?
What is the structural damage to the house?
What measures should be taken to stop the sinking?
What fortifications are needed to restore the security of the compromised house?
How profitable is it to preserve the building?

Indirect signals for movement in the foundations of the houses are sloping doors and windows, jamming in the boxes - difficult to open and close. Visually, the processes of subsidence in the foundations are accompanied by the formation of inclined cracks on the plinth, around windows and doors, as well as oblique cracks on the inner and outer walls.

The first and most important thing in the occurrence of cracks from subsidence is to determine to what extent the condition of the structure ensures the safety of its occupants. The subsidence of the foundations inevitably reduces the security of the building you inhabit and is a prerequisite for accidents with material and human losses. Uneven sinking of parts of the foundations can form cracks in all load-bearing elements. In addition to the walls, cracks can continue in the floor slabs and columns. Another negative effect is the accumulation of additional stresses in the materials of the structure, making it more vulnerable to other impacts, especially in an earthquake.

The next potential hazards to consider when laying the foundations are the condition of the house cladding, chimneys and other elements that endanger the safety of cars and people in the immediate vicinity. Increasingly, we are witnessing traces of fallen plaster on sidewalks and the roadway. Even with small sizes, falling materials can cause great damage. According to Art. 195 of the Spatial Development Actthe responsibility is sought entirely by the owners of the collapsing property.

After determining the current state of the building and its facade elements, we proceed to discover the cause of the uneven sinking. In some cases, this is a combination of several factors.

Structural survey and geological survey

This stage is accompanied by an investment by the owners. Proper identification of the causes and selection of adequate strengthening measures are the most important parts of a project. Choosing a highly qualified design engineer can save a lot of unnecessary costs for the investor in the future. Assembling a complete engineering picture gives clarity about the value of the project and its final profitability.

Foundation in "weak" soils

Practice shows that the most common cause of such frequent subsidence is the foundation in "weak" soils. The change of the groundwater level in them activates the processes of swelling and compaction, causing cyclic movements in the foundations. The change of the water content in the soils changes their consistency and mechanical indicators.

Therefore, lowering the water level by building sidewalks and walkways around the house, drainage systems and diverting roof water away from the foundations are sometimes sufficient measures to stabilize the foundations.

In cases where these measures are implemented, but the subsidence of the foundations and cracks on the load-bearing structure continue, it is mandatory to conduct a geological survey. It can also be done in the initial stage, which in the general case saves significant funds for useless drainage activities, as well as time for the owners. The data from the geological report clearly show the composition and mechanical parameters of the soil, as well as the most optimal measures to solve the problem.

Accidents in water supply or sewerage systems

Another common cause of subsidence is accidents in the water or sewage systems near the foundations. Their localization and repair is a difficult and expensive task that requires special equipment and knowledge. The study of groundwater for high content of chlorine and other chemical elements, not typical for rainwater, is a reliable indicator of leaks from the water transmission system. In addition to raising the water level, leaks form cavities in the earth's crust, freeing up space for soil movement around and under buildings.

Construction on landslide sites

More than 1600 landslides have been registered on the territory of Bulgaria. Construction on landslides is a risky and often unprofitable endeavor. Houses built on shallow joints can be successfully fortified, unlike those built on deep joints. In the second case, drainage of large areas is the only way out.

Activation of landslide movements

Most fescue masses are affected by soil moisture and are activated in the spring from March to May or in the fall - October and November. Reconstruction and accidents in the water supply and sewerage network are also prerequisites for activation of landslide processes dictated by the human factor. The displacement of foundations and whole houses from the movements of large earth masses is characterized by its greater speed and real danger of destruction. Adequate solution of already existing movements and subsidence in the foundations can be taken only after preliminary geological studies. Determining the water horizon, the depth of the layers and their soil characteristics are the fulcrums necessary for the preparation of an effective project. Possible options are soil consolidation, drainage, construction of support facilities, pilot steps or other measures. The concept and scope of measures to stop soil movements are strictly site-specific and vary widely.

Excavation works nearby

Excavation works next to existing buildings also pose a real danger of uneven sinking of the foundations of existing buildings in the vicinity. Depending on the depth of the trench, the type of fortification, groundwater and the nature of the soil, this effect can be observed up to several tens of meters away. The rapid drainage and the lowering of the water horizon in the area of ​​the new construction release empty cavities in the soil, which leads to its compaction and contraction. Unfortunately, these effects are difficult to avoid and usually remain at the expense of the victims.

Shallow foundation

Shallow foundation, above the freezing point, which varies from 70 to 120 cm depending on the soil and the region, is also one of the prerequisites for uneven subsidence in the foundations. This process can be explained by the cycles of freezing and thawing of water in the soil. Re-freezing and thawing of the water in the composition of the soil leads to destruction (destruction) of its integrity and opening of cavities. Another negative aspect of the shallow foundation of the houses is observed in the cases when the excavation does not reach a solid earth layer or the penetration into it is not enough. It is recommended that the foundations of the houses enter at least 40 cm into the "healthy" soil.

These are the most common causes of uneven sinking in the foundations, and of course there are others. Once measures have been taken to eliminate them, the next step is to monitor the building. In some solutions, the fortification measures do not have an immediate effect on the building. There is a gradual attenuation in subsidence and opening of cracks. Only after these processes are completely stopped is it reasonable to proceed to the restoration of lost load-bearing capacity in the structure. These activities are expressed in the filling of cracks, additional reinforcement and others.

What not to do!

Advice from acquaintances, even if they are regular civil engineers. Taking fortification measures to save a sinking building is a complex task. For its correct solution it is necessary to collect information about the type of foundation, soil characteristics, water horizon, the condition of the building. Blind execution of "heels" and framing rings very often leads to even a negative effect. The weight of the building increases significantly above the permissible for the soil. Once implemented, these measures are irreversible or extremely expensive to correct.

As a final conclusion, it can be summarized that the settlement of the foundations is a complex process with many possible causes and solutions. The research activities in the initial stage, together with the design, are the most important moments for which no money should be saved. Sometimes the sums for strengthening and drainage are high, but this should not stop the owners from taking measures to preserve their real estate and secure their houses against accidents. Postponement of building reinforcement activities leads to increased damage, significant additional costs, risks and undesirable consequences.

You can contact us for assistance in diagnosing the building, preparing a project for fortification activities, as well as their subsequent implementation.  

Do not hesitate to contact us!  

Author: Dr. Eng. Teodor Todorov


The purchase and repair of an old house is done for investment purposes or most often for personal use. There is a tendency for future owners to make their choice for a new home solely on the basis of location and prices per square meter. Followed by the fastest cosmetic repair and application. However, there are many cases in which the initial budget is seriously burdened by subsequent structural defects of the new acquisition. Regardless of the future intentions of the buyer, the condition of the building is decisive for the price he should pay for its purchase. Some of the defects in the old houses are visible and can be easily noticed. Sometimes, however, they are cleverly disguised by the seller in order to increase the sale price of the property. In other cases, defects and damages can only be detected by a well-known specialist. In the following lines we will focus on the most common problems when buying an old house and their role in making the final investment decision.

Condition and coverage of the roof structure

Given the average price for repair (about BGN 20 / sq.m.) Or replacement of the roof structure (BGN 90-140 / sq.m.), It is mandatory to pay special attention to the condition of the roof. Traces of leaks and rotten wood indicate considerable additional costs that you should anticipate after buying the property.


It is not uncommon for longer leaks in the roof to affect the floor structure of the lower floors. Sellers often hide these "details" with an old rug or linoleum just below the leak.

Load-bearing structure of the building

According to statistics from the National Statistical Institute, 1447,012 buildings in the country have a masonry / brick supporting structure. About 90% of them are on one or two floors. What should we look for when choosing a house or a larger building with masonry load-bearing walls?

Avoid buying buildings with a "Prussian vault" ceiling or the presence of "short" columns

Analyzes of past earthquakes unequivocally show one thing - the mentioned elements make the building especially sensitive to earthquakes. Sometimes the presence of only one of these elements can weaken the structure at times.

Avoid buying a building with storey wooden beams

Houses with mezzanine levels from wooden joists they also pose earthquake hazards, especially when they are on more than two floors, with high ceilings and large rooms. The choice of the right system for strengthening and the preparation of a constructively sustainable project can be performed only by an expert-designer in the field. The preparation of a price offer can be done after inspection. In some cases, in order to prepare an adequate offer, a preliminary inspection of structural elements is required. The aim is to ensure the co-operation between the old structure and the reinforcement system.


Visible defects in the construction

The main causes of defects in old houses are related to:

  • reduction in time of the qualities of the bearing materialsDue to long cycles of freezing-thawing, chemical agents, direct sunlight, wetting by atmospheric or capillary waters, the bearing capacity of building materials decreases. In masonry structures this effect is expressed in the surface collapse of bricks and mortar;

  • overload of individual elements
    This condition of the vertical columns or walls can be easily assumed in the presence of "displacement" of pieces of masonry;
  • uneven subsidence of the foundationsCause oblique and vertical one-way cracks. In addition to the visual shortcomings, this process generates great additional effort in the load-bearing elements. Leads to damage to the integrity of the building and risk of accident. When the foundations settle, repairs are expensive and often unprofitable;

  • high humidity
    Високата влажност може да се появи навсякъде, като най-често можем да я срещнем в подземните помещения на къщата. Тя е съпроводена от нарушен външен вид на засегнатите от влагата места, развитие на нездравословни мухълът и плесен. В краткосрочен план може да се посочи намалената носимоспособност на зидарията при наличие на висока влажност.  Дългосрочните конструктивни последици от влагата са прогресивната корозия и намаляване носещата способност и на метални и неметални строителни материали във времето;

visoka vlaga maze

  • floods;

The most affected houses by floods are those with lime or clay mortar between the bricks. Brick and pressed bricks also suffer significant damage even with short-term wetting. The wooden elements in the joists and walls could also be significantly affected. Buying a house in an area affected by past floods is a risky decision. Preliminary consultation with a construction specialist is desirable.

  • earthquake impacts
    Structures affected by earthquakes have characteristic slopes, two-way cracks, most often on the vertical elements.

 Ремонтните дейности за отстраняването им са с висока стойност и понякога може да се окажат нерентабилни. Именно това се оказва и причината за продажба на не малък брой стари къщи. За съжаление, преди продажбата собствениците често  умишлено прикриват пукнатините в засегнатите участъци.

Quality of construction

Statistics of the causes that led to defects, damages and accidents of building structures for the period 1966-2013, shows as the main cause of implementation errors.

On initial inspection of an old house can be considered a serious drawback:

  • insufficient vibration of the concrete mixture during pouring;

  • insufficient coverage of the reinforcement;

  • stratification of the concrete mixture;

  • "Entry" of solid bricks into the column;

In some cases, these deficiencies are correctable, other times not. In any case, the cost of their repair by the new owners should not be overlooked.

"Permissible" but undesirable defects can be mentioned the lack of a vertical joint between the bricks and theirs heterogeneity by color, indicating low quality of the bricks.

Construction of a wing

The construction of a wing allows the development of a higher building density. However, in the case of individual buildings of more than three storeys, mandatory structural requirements must be observed to ensure their safety in the event of an earthquake.

The main thing to pay attention to is that the distance between the walls of the wing should be at least 7-10cm and to be missing discrepancies in height of the floor slabs. Roughly speaking, the different natural oscillation frequency of buildings during an earthquake could lead to impacts between them. The effect of such an interaction affects their vertical elements and is highly destructive.

Globally, new standards for the design, reinforcement and conservation of masonry structures continue to be developed and introduced. Constant technological progress in this area enables owners to extend the life of their building and at the same time increase its operational security. Gradually, these trends are entering our construction practice, reducing the cost of repairs without sacrificing quality.

You can contact us for assistance in choosing a new, safer home. Making the right, informed decision when buying saves big costs for owners in the future.

Do not hesitate to contact us!  

Author: Dr. Eng. Teodor Todorov