The TBDY 2018 Seismic Code Guide: How a Home Buyer Reads Whether a Building Is Safe

When buying a home, the most accurate question is not about the view or the square meters; it is whether the building is safe. That question has an engineering answer, and Turkey's seismic code, which came into force in 2018, frames that answer quite clearly. The aim of this article is not to make you memorize the code like an engineer, but to help you read it like a buyer and ask the right questions.

The core difference of the current code is that it does not treat a building with a single crude safe–unsafe distinction. Instead, it sets a graded performance expectation according to the size of the earthquake. In a minor quake the building should suffer almost no damage; in a very large one people must be able to leave safely. At both ends, the expected behavior of the building is defined in advance.

What the Performance Targets Tell You

Performance targets sit at the heart of the code. They are tiers that describe the condition of a building after an earthquake. In plain language, you can think of the four levels like this:

• ·Uninterrupted Use (KK): The building keeps functioning with almost no disruption after the quake. This is the highest expectation, sought in critical structures such as hospitals and fire stations.
• ·Immediate Occupancy (HK): Structural damage is very limited and the building can be reused within a short time.
• ·Life Safety (CG): The building is damaged but does not collapse, and occupants can evacuate safely. This is the baseline target for ordinary homes.
• ·Collapse Prevention (GÖ): Heavy damage is accepted, but partial or total collapse is prevented; this is the last line of defense.

As a home buyer, it is enough to know this: for a normal apartment building, the design is expected to ensure life safety in a very large earthquake and to keep the building usable in the more frequent, moderate quakes. When these performance targets are defined in the project documents, it shows the building was designed against a deliberate expectation rather than at random.

Why the Soil Class Report Is the First Document to Check

An earthquake reaches a building through the ground. The same project behaves one way on solid rock and quite differently on loose, water-saturated soil. That is why every serious project rests on a geotechnical survey and a soil class definition based on it.

The soil class, put simply, tells you how much the ground will amplify the earthquake. Soft soils can magnify the seismic wave, increasing the load on the structure. A good design does not assume the ground is stronger than it is; it calculates loads according to the real soil class. As a buyer, asking whether the soil survey exists and learning which soil class the building was designed for is the most practical way to gauge the seriousness of a project.

The soil survey also evaluates issues such as liquefaction, settlement and slope stability. If this report is missing or treated superficially, every calculation built on top of it is open to question.

Building Supervision: Bringing Paper Safety to the Site

Drawing up a good project is one thing; executing it correctly on site is another. Independent building supervision exists precisely to close that gap. From concrete quality to rebar placement, from formwork dimensions to workmanship, it ensures that every critical stage is checked by an eye independent of the contractor.

For a buyer, supervision means this: the safety of the building is not left to the word of a single party. The fact that supervision records, concrete sample results and inspection reports are kept is the most concrete sign that the project is being stood behind. You have every right to request these documents.

What to Look for in the Contract

Trust is measured by written commitments, not verbal promises. When the following headings appear clearly in a housing contract, they protect you from much future uncertainty:

• ·Compliance with the seismic code and relevant standards should be committed to explicitly.
• ·Independent building supervision and your access to inspection documents should be put in writing.
• ·The classes of concrete and reinforcement to be used, along with key material qualities, should be specified.
• ·The delivery date, delay conditions and penalty clauses should be clear.
• ·Common areas, annexes and the occupancy permit process should be defined.
• ·Liability and warranty in case of defective work should be set out in writing.

If you are the landowner in a land-for-flat arrangement, the technical qualities of the construction belong in the contract alongside the share ratio. If you are a turnkey buyer, it is entirely reasonable to ask for the material and equipment list of the flat to be delivered as an annex.

Key Differences from Buildings Under Older Codes

Buildings constructed under earlier codes are not necessarily unsafe; but the current code raises the bar at several points. The most notable differences can be summarized as follows:

1. Design rests on defined performance targets for different earthquake sizes, rather than a single notion of safety.
2. Ground behavior is treated in more detail; soil class and local effects enter the calculation more strongly.
3. How the structure deforms during a quake, namely its ductility and drift behavior, is controlled more rigorously.
4. Calculation methods and modeling expectations have been updated in line with current engineering knowledge.

For this reason, when buying an older building it is wise to ask when and under which understanding it was built, and whether it has any retrofitting history. In a new project, this framework is expected to have been observed from the outset.

Common Mistakes

The most frequent errors on the buyer's side usually stem not from a lack of knowledge but from failing to ask the right question:

• ·Looking only at the facade, kitchen and view while skipping questions about the structural system and the ground.
• ·Deciding without ever seeing the soil survey report or asking about its content.
• ·Treating supervision as a formality and not requesting the inspection documents.
• ·Settling for verbal assurances and not having technical commitments written into the contract.
• ·Leaving official processes such as the occupancy permit until after delivery.
• ·In a very old building, acting on price alone without questioning any retrofitting history.

The common feature of these mistakes is that all of them can be prevented by a few questions asked in advance.

A Simple Checklist Framework for the Buyer

The table below summarizes the four core headings to keep in mind when assessing a building:

Looked at together, these four headings turn the safety question about a building from an emotional guess into an assessment grounded in concrete documents.

At Çetin İnşaat, we have worked in Ankara with the same discipline for three generations since 1972; we treat compliance with the seismic and insulation standards, independent building supervision and clarity in the contract not as a feature to be sold, but as a promise given from the very start. In every project, above all CETIN Avenue underway in Pursaklar, we regard answering this safety question with documents as our basic responsibility to the buyer.