Restoration / Architecture · Design and Construction
Guide · YOY Mimarlık
How is a historic building at risk assessed?
The “risk assessment” made before an earthquake and the “damage assessment” made after one are not the same thing. Their methods differ, and so do their legal consequences. Here is which is needed when in a registered building, and where the regulations leave a gap.
Two separate tasks: risk assessment and damage assessment
The two terms are used interchangeably in everyday speech, yet in the conservation literature they have separate definitions. A risk assessment is made before a disaster: the building’s present seismic safety is analysed, those at risk are identified, and strengthening is prioritised. A damage assessment is made after one: the level of damage the building has taken is established, and from it follow the priorities for making safe and for repair.
The difference is not only one of timing. The purpose of a risk assessment is to prevent destruction; the purpose of a damage assessment is to save what remains after it. Part of the difficulty experienced in Antakya after 6 February 2023 arose because no systematic pre-earthquake risk assessment existed for the registered building stock.
What they share is this: both require the building to have been documented. For a building without a measured survey, neither can risk be measured nor damage be properly assessed. Documentation is the first step of the conservation process and equally the groundwork of disaster management.
Why the work is done in two stages
Resolving the seismic performance of a historic building through laboratory testing and numerical modelling is long and costly work. It can be done for a single building, but not for hundreds at once across an urban conservation area. International practice therefore follows a two-stage path.
The first stage is rapid, observational and systematic: the building is screened on a form against defined criteria. The aim is not to give a final answer but to produce an order of priority — which buildings should go forward to detailed examination, which need making safe at once. The second stage is detailed analysis: material samples are taken, non-destructive or minimally destructive tests are made, a numerical model is built and seismic performance is calculated.
The ICOMOS principles for the structural restoration of architectural heritage recommend the same integrated approach: qualitative (observational) and quantitative (measured) methods should run together. A historic building is not homogeneous; centuries of additions, repairs and decay make it uncertain how far a mathematical model reflects reality. Observation covers the model’s blind spots.
Where the regulations leave a gap
Seismic safety in Türkiye is governed by two main texts: the Turkish Building Earthquake Code and the Principles for the Identification of Risky Buildings prepared under Law no. 6306. These group buildings by structural system as reinforced concrete, steel, masonry and mixed. Neither was drawn up for historic buildings.
The consequence is that no legally adopted preliminary seismic risk assessment guide, prepared according to the particular character of historic buildings, exists for a registered building. Model proposals developed in academia exist, but they are not instruments written into the regulations. While Italy and the United States have developed detailed typology-based damage assessment forms for both monumental and vernacular buildings, in Türkiye the gap remains.
In practice this gap turns every building into a separate case file. In a registered building a demolition decision can be taken only by the Regional Conservation Board, and the form and character of the intervention are likewise settled by the board in light of the building’s physical condition. There is no standard threshold — the strength of the file is what counts.
Modern systems in strengthening are now explicitly defined
A long-contested question was settled at the beginning of 2024 by the principle decision on the strengthening of immovable cultural assets requiring protection. It states that where a ground survey carried out for substantial repair leads to modern systems — bored piles, seismic isolators, raft foundations — being proposed to protect the building from earthquake effects, the relevant basement drawings are to be assessed by the Conservation Boards.
For an owner the implication matters: modern strengthening methods are not forbidden outright in a registered building. They must, however, rest on a ground survey and be submitted separately for board approval. The blanket judgement that “concrete cannot be poured in a registered building” is not correct; what is correct is that every intervention is assessed by the board together with its justification.
A strengthening decision therefore cannot be thought of separately from the restoration project. Ground survey, structural analysis and conservation principles must meet in a single file. Our approach is to discuss strengthening at the beginning rather than at the end: to measure, while taking the survey, in the knowledge of which data the structural analysis will later need.
Maintenance is a seismic measure too
Debate about seismic safety usually runs on strengthening: steel, piles, isolators. Yet among the things that decide how a building behaves in an earthquake, the state of its materials beforehand comes first. A wall that has taken up water, whose mortar has broken down and whose cramps have rusted, behaves differently in the same earthquake from a sound one.
A comparison made with a thermal camera on registered buildings in Antakya makes this measurable. In restored buildings the thermal transitions are soft and even; there is no decay in material or structure and no water ingress. In unrestored ones the transitions are sharp; damp and ground water have caused physical and chemical losses in the facing materials, in some buildings the damage has advanced as far as the structural system, and partial collapses have begun.
Two conclusions follow. First, thermography is a cheap and non-destructive tool for preliminary assessment: it shows damp inside a wall, hidden leaks and differences in filling without touching the surface. In first-stage screening it makes visible what the eye cannot see.
Second, and more important: maintenance is not an expense that can be deferred. Dealing with a leaking roof, a failed joint or a blocked water course while it is small is both cheaper than repairing the structure years later and costs less of the building’s original fabric. Preparing for an earthquake usually begins not with a large strengthening project but with a simple maintenance calendar.
Frequently Asked Questions
My building is registered; can I get a risky-building report from the municipality?
An identification of a risky building under Law no. 6306 does not open a direct route to demolition for a registered immovable cultural asset. In a registered building a demolition decision — including where a danger of collapse is claimed — can be taken only by the Regional Conservation Board. If the building is in a dangerous state, the correct course is to apply to the board with a documented damage assessment and a proposal for emergency stabilisation.
If a rapid screening has been done, is detailed analysis still needed?
It is. Rapid screening is a tool for setting priorities, not a certificate of safety. It says “this building should go forward to detailed examination” or “this building needs making safe at once”; it does not say “this building is earthquake-resistant”. A strengthening project can only be built on second-stage analysis, with material testing and a numerical model.
Does detailed analysis damage the building?
It is managed through the choice of method. The sequence begins with non-destructive techniques, moving where necessary to minimally destructive and only last to destructive tests. Where samples are taken, they come from the points of lowest documentary value and highest representative value, and the sampling points are marked on the survey drawings. The conservation principle is the same here: the most information for the least intervention.
Source
The principal source for the methods and regulatory framework in this article: Naycı, N. (2023). A Discussion on Risk Assessment Methodologies for Historic Buildings after 06 February 2023 Earthquakes. SKETCH — Journal of City and Regional Planning, 5 (2), 54–75. DOI: 10.5281/zenodo.10986364. Also ICOMOS (2003), Principles for the Analysis, Conservation and Structural Restoration of Architectural Heritage, and principle decisions nos. 660, 24, 35 and 110 of the High Council for the Conservation of Cultural Property. For the thermal camera comparison: Dönmez, S. (2023). An Analysis of the Structural Systems of Traditional Antakya Houses in the Context of Physical Environment Control. Master’s thesis, Adana Alparslan Türkeş Science and Technology University. The commentary and practical recommendations are our own; regulations may be updated, and confirmation should be sought from the relevant Regional Conservation Board Directorate before proceeding.