The structure cannot be seen
once the walls are plastered.
Six systems appear in listings under two words, and the difference shows up in renovation, in valuation and in an earthquake.
Six structures, not two The listing reduces them to “old” and “new”
In Varna, buildings from six different structural systems are on sale, and listings sort them into two columns.
Timber-joist floors (гредоред): load-bearing brick walls with timber floor structures, in the city centre until about the 1950s. Brick with monolithic reinforced concrete slabs, framed with columns, beams and ring beams, from the 1950s to today. Large-panel construction (едропанелно строителство), from the late 1950s to the first half of the 1990s, in which the load is carried by the transverse wall panels and the central longitudinal wall. Large-area formwork (едроплощен кофраж), that is, monolithic reinforced concrete cast on site, widespread in the 1980s. Lift-slab construction (пакетно повдигани плочи), a frame system without beams. And monolithic reinforced concrete with a frame, shear walls and rigid cores, from the 1990s to today.
Each of the six behaves differently in an earthquake, in renovation and in a bank valuation, and what can be touched changes completely from system to system.
One number explains why this is a topic for 2026 and not for 1985. According to National Statistical Institute (НСИ) data for the second quarter of 2026, of 1,269 new residential buildings in the country 77.8% are reinforced concrete, 19.6% brick and 0.6% panel. So new construction is practically one structure. The whole debate over “what the structure is” concerns the existing stock, not the new one. The choice between the two is covered in Panel block or new construction.
EPK is not panel
and this is the most common mistake in listings
The abbreviation EPK (ЕПК) stands for large-area formwork. It is a technology for buildings made of monolithic reinforced concrete, using large reusable formwork panels. The concrete is cast on site, so there are no joints between elements, because there are no separate elements.
Panel is the exact opposite. The elements are made in a factory and assembled on site, and until the end of the 1980s thirty house-building plants were operating in Bulgaria. The seismic load-bearing capacity of such a building lies in the joints and the welded connections within them, not in the panel itself: the standard requires at least one square centimetre of metal connections per linear metre of joint, spaced no more than a metre and a half apart. That is also why the condition of the joints is a structural question, not a cosmetic one.
Two opposite technologies from the same decade, yet on the portals they appear under the shared heading “old construction” and often under the shared label “EPK/PK” (ЕПК/ПК). In our sample of 1,345 Varna listings, downloaded on 22 August 2026, only 34 carry this label.
What goes wrong in practice: the buyer pays a premium for monolithic concrete and buys panel. Or turns down EPK because they heard it as “panel”. The difference cannot be seen on a viewing once the walls are plastered. It can be seen in the design documentation and in the structural engineer’s opinion (конструктивно становище), that is, in documents nobody asks for until it is too late.
Varna is right on the threshold Kc = 0.10, meaning intensity VII
The current ordinance on the design of buildings and facilities in earthquake zones (наредба за проектиране на сгради и съоръжения в земетръсни райони) dates from 27 January 2012. In the annex listing settlements, Varna has a seismic coefficient of 0.10, which on the map for a thousand-year period corresponds to intensity VII. For comparison, Burgas is also 0.10, Veliko Tarnovo 0.15, Sofia and Blagoevgrad 0.27.
The number is not decorative. With a coefficient between 0.05 and 0.10, the ordinance allows a building not to be calculated for earthquakes at all, provided the structural requirements are met. With Kc equal to or greater than 0.10, calculating seismic actions is mandatory for all buildings except the lowest importance class. Varna is on the strict side of the threshold, and not by chance: in 1901, in the Shabla and Kaliakra zone, about ninety kilometres from here, earthquakes of magnitude 7.2 and 7.1 were recorded.
The same ordinance also contains a table of permitted height and number of storeys. At Varna’s coefficient, monolithic reinforced concrete and steel frames have no limit on storeys, large-panel and lift-slab buildings go up to 12 storeys, brick with monolithic slabs up to 5 storeys, and a brick building with timber floor structures up to 2 storeys. That is exactly why 77.8% of new construction is monolithic reinforced concrete, and not because it sounds more modern.
“Unsecured” is a legal definition, not an assessment
And the dispute over it is not settled
The supplementary provisions of the current ordinance give two definitions that almost no buyer has heard of. “Secured buildings” (осигурени сгради) are those designed in accordance with the 1987 standards. “Unsecured buildings” (неосигурени сгради) are those built before 1987.
So by the letter of the current text, every residential building in Varna from before 1987 is “unsecured”: panel, EPK, lift-slab and brick alike. This is not an assessment of the particular building. It is a legal definition, but it is the one that the structural survey, the technical passport (технически паспорт) and every structural engineer work with.
And here comes the part that cannot be quoted one-sidedly. The authors of the standards themselves, Prof. Nikola Ignatiev and Prof. Petar Sotirov of the University of Architecture, Civil Engineering and Geodesy, UACEG (УАСГ), published an analysis according to which, in most of the cases examined, the seismic forces under the 1964 standards come out larger than those under the 1987 standards, and they conclude that buildings designed after 1964 should not be classified as unsecured. Straight after that they add the opposite caveat: the design requirements in the 1987 standards are stricter, and the capacity design method only arrives with Eurocode 8.
The dispute between the current ordinance and the authors of the previous standards is not settled. For the buyer, the meaning is the opposite of reassurance: the year of construction is not the answer. The answer lies in how the particular building was actually built, and it can only be seen in a structural survey.
Eight centimetres decide everything and trigger a requirement for the whole building
The data for the most widespread panel type in Bulgaria, the Bs-69-Sf system (Бс-69-Сф), come from a peer-reviewed UACEG paper, presented at a conference in Varna in 2020 and based on the archived design documentation.
The layout is cellular. The load-bearing walls are the transverse walls, including the gable facade walls, plus the central longitudinal wall. The internal load-bearing wall panels are 14 cm, while the partition panels, that is, the non-load-bearing ones, are 6 cm. The facade panels along the longitudinal axes carry no load and hang from facade beams.
There is one practical conclusion: in such a building, the only thing that can be touched is the 6 cm panels. Everything from 14 upwards is load-bearing and also takes the horizontal forces from wind and earthquakes. The difference is eight centimetres, and it cannot be seen while the wall is plastered.
If someone still decides to remove it, the ordinance sets off a chain that surprises everyone. Construction works involving a change to the structure, including internal alterations, are permitted only with a survey of the entire building and a registered technical passport, a positive assessment of seismic safety, compliance with the permitted height and number of storeys, and an approved investment project. One owner who wants to open the kitchen into the living room triggers a requirement for the whole building, which depends on the neighbours.
And most Varna blocks have no such passport: an amendment in 2021 repealed the deadlines for private buildings, leaving only a deadline of 31 December 2032 for public property. A passport is not made until it is needed, and it is needed exactly when someone wants to make alterations. What skipping it costs is the subject of Illegal alterations: the fine under the Spatial Development Act (ЗУТ) is BGN 1,000 to 10,000, which is about €511 to €5,113, our conversion, plus an order for removal at the expense of whoever did the work. It is usually discovered at the next sale, when the new buyer has already paid.
The number the listing does not show
2.43 against a standard of 0.26
Today’s ordinance requires external walls bordering outside air to have a heat transfer coefficient of no more than 0.26 W/m²K. We took an official energy efficiency project for a panel block, prepared for retrofitting, and calculated the same cross-section without the insulation, using the same layers and coefficients. The bare 25 cm panel wall gives U of about 2.43 W/m²K, that is, about 9.3 times above the standard. The same wall with nine centimetres of insulation, as in the project, gives 0.335, that is, about 1.3 times above it.
The calculation is ours, for the specific cross-section from the specific project. It is not a universal value for a “panel block” and is used only for the order of magnitude. And the order of magnitude is what matters: the difference between a retrofitted and a non-retrofitted panel block is not “warmer”, but the difference between a wall that misses the requirement nearly tenfold and a wall that meets it. The listing shows both the same way.
The same goes for noise: the ordinance requires floors between dwellings to provide airborne sound insulation of at least 54 dB. The requirement exists and is measured. Whether a particular building meets it is checked by measurement, not by a listing.
Where the structure enters the bank’s calculation Twice, and both times invisibly
The buyer calculates a 15% down payment on the price. The cap set by the Bulgarian National Bank (БНБ) is 85% of the valuation, and the valuation is the opinion of a valuer who looks at the structure and the remaining service life. The full caps and what they changed are in The BNB tightened lending, and the mechanics of the loan itself in Mortgage loan step by step.
The arithmetic is short and unpleasant. With a price of €100,000 and a valuation of €90,000, the maximum loan is €76,500. So the down payment is not €15,000 but €23,500. The €8,500 difference has to be found in cash between signing the preliminary contract (предварителен договор) and the deal at the notary. Or the deposit is lost.
The second point is the repayment term. Here we deliberately give no number: the only professional source with percentages by structure type is from 2019, and for 2025 and 2026 there is no statement from a bank or the BNB on this criterion. That is why there is no figure here for “how much they lend on a panel block”. There is only a mechanism: the structure enters the calculation twice, through the valuation and through the term, and the buyer sees both only when the bank answers.
The valuer also looks at the remaining service life, and here a much-quoted number is understood the wrong way round. The design service life of a residential structure under the ordinance is 50 years, but the ordinance itself defines it as a period of use “with normal maintenance and without the need for significant repairs”. So it does not mean “then it falls down”, but “no significant repairs are expected until then”.
Numbers that are true on paper and false in practice
Watch the denominator
Large-panel construction in Bulgaria has produced over 700,000 homes in 18,900 buildings, and in the breakdown by city Sofia has 28.5%, Plovdiv 8.2%, Varna 8.1%. So by number of panel buildings, Varna is the third panel city in the country.
Against this stands another statistic that is regularly quoted in the opposite sense. According to NSI data on the housing stock in Varna region at the end of 2024, brick buildings are 87.2% and panel buildings 1.3%. The number looks like the end of the conversation, and it is not.
These percentages are of buildings, not of homes. A village house is one building with one home, while a panel block is one building with sixty to a hundred. On top of that, 44.1% of the buildings in the region are in villages. So “1.3% panel” does not mean that 1.3% of people in Varna live in panel buildings. The denominator makes the number false in practice, even though it is true on paper. How many homes in the region are in panel buildings has not been published, so there is no such percentage here.
Our own sample shows the third level of the same problem. Of 1,345 listings in six Varna neighbourhoods, downloaded using the explicit filter for construction type, 81% are brick, 16.4% panel and 2.5% EPK. But by neighbourhood the distribution is completely different: in Vladislavovo panel is 35.9% of supply, in Pobeda 0.9%, in the Pchelina area zero. And the same Vladislavovo has a median construction year of 2025, because panel is the stock and new construction is the flow.
Price confirms it from the other side: the median asking price for a one-bedroom flat in Vladislavovo is €1,576 per sq m across 106 listings, against €2,220 in Troshevo and €2,805 in the Centre (alo.bg, 4 September 2026). The medians are by neighbourhood and by asking price, not by structure and not by completed sales, so they are not the price of a specific property. But they show one thing: the difference within one neighbourhood is bigger than between two neighbourhoods, and it is hidden behind a shared median. The comparison between the neighbourhoods is in Varna: six neighbourhoods.
So the question is not “panel or brick”. It is which of the six systems the particular building is, under which standard it was calculated, whether it has a survey and a passport, and what of this the valuer will see. None of these answers is in the listing.
Frequently asked questions
Is EPK the same as panel?
No, the two are structurally opposite. EPK stands for large-area formwork and is a technology for buildings made of monolithic reinforced concrete, cast on site in large reusable formwork panels, so there are no separate elements and no joints between them. Panels are made in a factory and assembled on site, and the seismic load-bearing capacity of such a building lies in the joints and the welded connections within them. In listings the two often appear under the shared label “EPK/PK”, and the difference cannot be seen on a viewing once the walls are plastered.
Is it true that every building from before 1987 is seismically unsecured?
It is a legal definition in the current ordinance on design in earthquake zones, not an assessment of the particular building: “unsecured” buildings are those built before 1987, whether they are panel, EPK, lift-slab or brick. At the same time, the authors of the previous standards published an analysis according to which, in most of the cases examined, the seismic forces under the 1964 standards come out larger than those under the 1987 standards, and they dispute the classification on its merits. The dispute is not settled. For the buyer the conclusion is the opposite of reassurance: the year of construction is not the answer, and how the particular building was actually built can only be seen in a structural survey.
Can a wall be removed in a panel apartment?
In the most widespread panel system in Bulgaria, the internal load-bearing wall panels are 14 centimetres and the non-load-bearing partition panels are 6 centimetres, and the difference cannot be seen through the plaster. Everything from 14 centimetres upwards is load-bearing and also takes the horizontal forces from wind and earthquakes. Separately, the ordinance permits construction works involving a change to the structure only with a survey of the entire building and a registered technical passport for the building, a positive assessment of seismic safety, compliance with the permitted height and number of storeys, and an approved investment project. So one owner triggers a requirement for the whole building, and most private blocks have no technical passport, because the deadline for them was repealed in 2021.
Does the structure affect the mortgage?
It enters the calculation twice, and both times indirectly. First through the valuation: the BNB cap is 85% of the valuation, not of the price, and the valuer looks at the structure and the remaining service life, so with a price of €100,000 and a valuation of €90,000 the down payment is not €15,000 but €23,500 in cash. Second through the repayment term, which may be shortened for older housing stock. We deliberately give no specific financing percentages by structure type: the only professional source with such figures is from 2019, and for 2025 and 2026 there is no public statement from a bank or the BNB on this criterion.
Looking at an apartment
in an old block?
This evening, ask for two things backed by a document: the structure type and the year of construction. Not from the words in the listing and not from the look of the facade, but on paper. If the seller cannot point to them, that in itself is information, because the same two lines will be needed by the valuer and by every structural engineer after that.
Send them to us together with the link to the listing and the floor. We send back an assessment of what the structure means for the renovation you are planning, which walls are probably off the table, what an alteration would trigger, and where the structure could hit the valuation before you reach the notary.
The assessment is commercial and practical. It is not a structural engineer’s opinion and does not replace a survey by a structural design engineer. The BGN amounts have been converted at the fixed rate of 1 EUR = 1.95583 BGN.
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