Defects in the client’s design: the contractor’s notification duty and liability defence

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Where a design, material or instruction supplied by the client is problematic, the contractor should not base its defence solely on having done what was requested. The Turkish Code of Obligations requires professional care in performance and immediate notice of circumstances jeopardising proper or timely completion. In a later defects claim, who prepared the design matters alongside when the risk was identified, how clearly it was notified and its connection to the loss. This article explains how a contractor can organise notification and evidence under a private-law contract for work.

1. What changes when the client supplies the design?

Article 471 of the Turkish Code of Obligations measures the contractor against the professional and technical conduct expected of a prudent contractor undertaking similar work. Identify who supplied the design or materials; supply by the client does not remove every duty of care. Distinguish contractual design, execution, checking and coordination duties. A drawing prepared by the client’s consultant and the contractor’s own execution detail should not automatically be treated as carrying identical responsibility.

Article 472 provides for seller-like liability for defects in materials supplied by the contractor, and a duty to use client-supplied materials carefully, account for them and return the surplus. Its final paragraph covers not only defective client-supplied materials or the designated site, but other circumstances jeopardising proper or timely performance. Design incompatibility is assessed within that framework against the facts. Not every technical uncertainty is a design defect, and not every design defect automatically establishes the client’s responsibility.

2. When and with what content should notice be given?

The final paragraph of Article 472 requires immediate notice; it grants no fixed seven- or thirty-day waiting entitlement. Record when the risk became apparent and which work could then be affected. Identify the design version, work item, observed problem and anticipated quality or timing consequence in the notice. A general statement that the design has problems may not show that the particular risk later disputed was explained. Connect the necessary technical assessment to a request for the client’s decision or revision.

The provision does not prescribe one mandatory form for every notice; nevertheless, clear content and traceable receipt matter for proof. Check contractual notice procedures, the recipient and authority to represent the client separately. Preserve attachments, the actual addressee and the response history when assessing an email, site record or letter. Sending a warning intended for the client only to a subcontractor or a person of uncertain authority does not automatically have the same legal effect. A later document must not be presented as replacing a notice never given earlier.

3. If the client insists on proceeding despite the warning

Under Article 476, the client cannot exercise defects rights where the defect results from its instruction despite the contractor’s express warning, or is otherwise attributable to the client. The defence requires assessment of more than the instruction: consider the express warning, the work to be carried out, the eventual defect and their connection. Retain the client’s response and distinguish instructions before and after the warning. An abstract disclaimer of responsibility does not replace technical causation analysis.

For example, the client may request a change to a waterproofing detail. A record merely showing that the contractor accepted the change differs from one explaining water-ingress risk at a specified junction, requesting revision and recording the client’s continued insistence. Even so, an express warning is not permission to perform work contrary to permits, mandatory technical rules or safety. Determine the relevant technical and legal procedure separately where safety or legality is involved; this guide does not authorise a general decision to continue or suspend work.

4. Why is the client’s consent alone insufficient in case law?

The Fifteenth Civil Chamber of the Court of Cassation’s decision of 11 December 2018, E.2018/1636, K.2018/4976 concerned an omitted fire escape and a boiler room built somewhere other than the approved design location. The contractors relied on the apartment owners’ consent. The Chamber found that performance of the general notification duty had not been alleged and proved, held rejection of the relevant claims incorrect and reversed the judgment. Consent and a warning explaining the risk’s consequences are therefore not interchangeable; the decision does not provide an approval model for unlawful work.

The Sixth Civil Chamber’s decision of 10 February 2022, E.2021/3310, K.2022/690 concerned work above a retaining wall built by another contractor and the subsequent collapse. The Chamber reversed for insufficient examination of the design, ground, additional load, effects of the work and the notification duty under Article 472. The conclusion is not that a contractor is free of responsibility whenever someone else built the wall. The decision calls for expert assessment linking different teams’ work and notification; it does not finally allocate fault.

5. Which records make the defence concrete?

The first group comprises the contract, allocation of duties and design versions: show which drawing was supplied by whom, when and with what authority. The second consists of technical records when the risk was identified: photographs, tests, measurements and relevant expert assessment. The third comprises the warning’s content, attachments, dispatch and receipt evidence, and the client’s response. The fourth shows the instruction under which execution continued and the resulting site condition. Where several causes exist, assess the contractor’s own workmanship or coordination contribution as well.

If work will be concealed, repaired or altered by another team, judicial preservation of evidence may be considered subject to the legal-interest requirement in Article 400 of the Code of Civil Procedure. Before proceedings, assess the court competent for the substantive claim or the civil court of peace where the item to be examined is located; after proceedings begin, only the court hearing the action is competent under Article 401. Preservation is not a substantive liability ruling and does not replace the warning. Under Article 190’s general burden-of-proof rule, a contractor relying on notification and instructions for a favourable legal consequence should prepare proof of those facts.

6. Immediate notice and defects limitation are different time rules

The contractor’s immediate notification duty under Article 472 must not be confused with the client’s examination and defects notice after delivery. Article 477 separately regulates acceptance and notice of subsequently emerging defects; assess acceptance effects and exceptions against the facts. Giving advance notice of a design risk, responding to a post-delivery defects notice and raising limitation are distinct tasks. One record does not automatically meet all their requirements.

Article 478 provides limitation periods for actions arising from defective work, running from delivery: two years for work other than immovable structures, five years for immovable structures, and twenty years irrespective of the work’s nature where the contractor is grossly at fault. These are not waiting periods for immediate notice. Establish whether delivery occurred, whether the allegation concerns a defect or another breach, and whether a special regime applies. Do not automatically assign five years to every construction dispute; the tool does not calculate an individual final date.

7. Distinguish notification, payment claims and proceedings

Giving risk notice does not automatically entitle the contractor to additional payment, an extension or termination. Examine the revision’s scope, contractual pricing structure, client cooperation and cause of delay separately. If rectification costs or delay penalties are demanded, identify the disputed work item, cause and amount. Match the notification file to a technical and contractual defence answering that demand; do not assume that issuing a warning extinguishes the opposing claim.

Court competence depends on the parties and transaction: examine commercial-court rules for commercial actions, consumer-court and relevant consumer-arbitration-board rules for consumer transactions, and general competence rules for other private-law disputes. Check pre-action mediation separately under Article 5/A of the Commercial Code for commercial monetary actions and Article 73/A of Law 6502, with its exceptions, for consumer-court proceedings. Assess the defendant’s domicile and contractual place of performance for ordinary territorial jurisdiction, subject to special or contractual rules. Do not automatically fit public works or mixed contracts involving property transfers into this guide.

8. A practical preparation sequence for the contractor

First identify the contract type, allocation of technical duties and operative design version. Then chronologically match discovery of the risk, the express warning, receipt by the appropriate recipient and the client’s response. Next review revision and actual execution and their connection to the alleged loss; preserve evidence that may change in time where needed. If litigation or formal enforcement has begun, have the actual service documents reviewed promptly. This sequence develops the defence from an assertion that the client requested the work into specific instructions, warnings and technical evidence.

This is general information based on sources checked on 1 November 2026. The full texts of two Court of Cassation decisions were read; their reasons for reversal are not presented as final findings of immunity or fault. Safety, permits, special public-works terms, consumer-specific provisions and other liability regimes require separate assessment. The full guide contains topic-specific questions, a separate document-selection step and an office-branded preparation report. An unselected record is not automatically missing or mandatory; the guide requests no personal data, stores no selections persistently and predicts no litigation outcome.

Sources

General information; individual documents, facts and procedures need separate review.

Defective designs and instructions: contractor warning and evidence guide

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