Who's Liable for Building Defects in Poland: Contractor, Site Manager or Designer?

Once a build or a major renovation is finished, a serious defect shows up: a structural wall cracks, the roof leaks, the floor subsides, the roof trusses warp. But several parties were working on site — the main contractor, one or more subcontractors, a site manager, sometimes a separate designer. The obvious question is: who do you hold responsible, and who do you send your claim to? The short answer: in the typical case, you (the investor/client) only have a direct contractual relationship with the main contractor, and it is the main contractor who is liable to you for the whole job in the first instance — even if the actual cause of the defect was a subcontractor's negligence, a site manager's mistake, or a design error. Here's why that's the rule, when liability can reach the other parties in the construction process directly, and how to work out in practice who really is at fault.

This guide is general legal information, not legal advice. How the rules apply depends on your individual circumstances, the wording of your contracts, your documentation and the applicable deadlines. Where advice or representation is needed, the matter should be assessed by a qualified Polish lawyer. Twoja Sprawa helps you organise the documents for that assessment.

Key points

• Your first port of call is usually the main contractor — that's who your contract is with, regardless of how many subcontractors actually worked on site.
• A subcontractor generally isn't liable to you directly for defects — they answer to the main contractor, unless you signed a separate contract with them yourself or the damage amounts to a tort (a civil wrong independent of any contract).
• The site manager (kierownik budowy) — the person with construction qualifications formally responsible for running the site — holds an independent regulated role and answers professionally for how the build was run, but that's a different route of liability from a civil claim over a defect.
• The designer is liable for a design error in the documentation, not for the quality of the workmanship — establishing whether the defect stems from the design or the execution is key.
• The distinction between a "design defect" and a "workmanship defect" decides who you pursue — and usually calls for an independent building expert's opinion.
• Your status (consumer, a trader treated as a consumer, or B2B) affects the scope of protection and the type of court proceedings available.
• Gather all the site paperwork: contracts, the site log/diary, handover reports, correspondence — that's what shows who was actually answerable for what.

Who's who on a Polish building site

Before you can pin down liability, it helps to map out the roles, because each one is governed by different rules:

• Investor (inwestor) — that's you: the person or company commissioning the build or renovation, and the party to the contract with the contractor.
• Main contractor (generalny wykonawca) — the firm you signed the building or works contract with; liable for the whole job, including anything it subcontracted out.
• Subcontractor (podwykonawca) — a firm or tradesperson the main contractor brought in for part of the works (e.g. the electrical, roofing or plumbing crew); usually contracted to the main contractor, not to you.
• Site manager (kierownik budowy) — a person holding construction qualifications, formally responsible for running the site in line with the design, the regulations and accepted technical practice; their role and duties derive from the Polish Construction Law Act (Prawo budowlane).
• Designer (projektant) — the author of the design documentation, liable for the correctness of the design solutions and the design's compliance with the regulations; on larger projects they may also provide "author's supervision" (nadzór autorski), i.e. ongoing design oversight during the build.
• Investor's site supervisor / clerk of works (inspektor nadzoru inwestorskiego), if one was appointed — represents your interests on site and checks the quality of the works; any failings on their part are a separate liability question.

The bigger the project, the more likely these roles are held by separate people. On a typical flat renovation, there's often just a contractor (sometimes with subcontractors) — a site manager and designer tend to appear mainly on works that require Polish building permission (pozwolenie na budowę) or a formal notification (zgłoszenie).

Before assessing your position, also work out your status. If you're building or renovating property for your own private use, you're normally a consumer — with wider protection, including under the statutory warranty for defects (rękojmia). If the project relates to your business activity, the B2B regime applies, under which some protections can be contractually limited, and any court dispute may proceed as a separate commercial case. Keep that distinction in mind for every point below.

Why you usually sue the main contractor, not the subcontractor

This is the key practical rule in this type of case: your counterparty is whoever you signed the contract with — almost always the main contractor. If the contractor subcontracted part of the works, it — not you — is the party to the contract with that subcontractor. In the relationship between you and the contractor, the rule is that the debtor (the contractor) is liable for the acts of the people it uses to perform its obligation as if those acts were its own. In practice, this means:

• You report the defect to the main contractor, even if you know a particular part of the works (e.g. the wiring) was done by a subcontractor.
• It's the contractor who settles up with the subcontractor on its own account, under the contract it signed with them (recourse claims, deductions, contractual penalties).
• You don't have to establish exactly which subcontractor was at fault in order to pursue the contractor — which makes your evidential position considerably simpler.

The exception is where you signed a separate contract directly with the subcontractor (say, you hired the electrical crew yourself, independently of the main contractor) — in that case you do have a direct contractual link with them, and it's them you pursue for the defective part.

When liability reaches the subcontractor directly

No contract with the subcontractor doesn't always mean you have no claim against them at all. Two scenarios are possible:

1. Tortious liability, independent of any contract. If the subcontractor's actions caused damage (e.g. they damaged a pipe or cable, flooded a unit, caused a fire), they may be liable under the general rules on liability for a civil wrong (tort), regardless of who they had a contract with. This is a separate basis from a contractual claim over a defect.
2. Joint and several liability for paying the subcontractor's fee — this, however, runs the other way (the investor and the main contractor can be jointly liable to the subcontractor for its unpaid fee), not liability of the subcontractor to the investor for a defect. Worth knowing, so you don't mix up two entirely different mechanisms.

In practice, if you want to pursue a claim directly against the subcontractor, it needs careful legal analysis — it's usually easier and more reliable to direct the claim to the main contractor, who's liable for the whole job, and let them settle up with the other firms involved.

When the site manager is liable

The site manager isn't normally a party to your contract — they're usually hired or delegated by the contractor, though on larger projects the investor sometimes appoints them directly. Their liability works differently from the contractor's:

• Professional liability — as someone holding an independent regulated technical role in construction, the site manager is subject to the Construction Law Act and to professional disciplinary liability before the relevant professional body (the Chamber of Civil Engineers, izba inżynierów budownictwa) for breaching their duties, including failures to supervise compliance with the design and the regulations. This is a disciplinary process, not a direct compensation claim for you.
• Civil liability — if the defect stems from the site manager's own failings (e.g. they allowed a departure from the design without approval, or didn't halt defective works), and there is an appropriate legal basis linking them to you, a claim under the general rules may be possible.
• Professional indemnity insurance — many site managers carry professional liability insurance; in practice, this is often the real source of any payout, so it's worth asking about it early on.

Reporting the matter to the Chamber of Civil Engineers (professional liability) and pursuing compensation (civil liability) are two separate tracks — they can run in parallel, but neither replaces the other.

When the designer is liable

The designer's liability concerns defects in the design, not the quality of the workmanship itself — and that distinction is crucial:

• Design defect (design error) — a flawed structural solution, incorrect calculations, a design that doesn't comply with technical-building regulations, or a significant element left out. The designer is liable for this under the contract for the design documentation (usually a "specific-task" contract, umowa o dzieło) and under the Construction Law Act provisions on a designer's duties. If an independent expert's report confirms a design error, you direct your compensation claim at the designer, not the contractor.
• Workmanship defect — the design was correct, but the contractor (or subcontractor) built it inconsistently with the documentation, or carelessly. The contractor, not the designer, is liable for this.
• Mixed situations — sometimes the design contained ambiguities that the contractor interpreted wrongly, or the site manager should have flagged a query to the designer and didn't. Working out the split of responsibility in these cases is usually the most contentious part, and typically needs an expert opinion.

If the designer also provided author's supervision (checking that the build matched the design as it progressed), their liability may extend to failings during construction, not just errors in the design itself — but again, that depends on the specific contract.

Establishing who's actually at fault — the role of an independent building expert

In disputes involving several parties, the weakest link is usually establishing the cause of the defect. Before you send any letter, it's worth doing the following:

• Commission an independent building expert's report (rzeczoznawca budowlany) — their job is to establish whether the defect stems from a design error, a workmanship error, faulty materials, or a supervision failure.
• Preserve the site paperwork: the site log/diary, the detailed working drawings, the interim handover reports, and correspondence with the site manager and designer.
• Don't remove evidence of the defect (e.g. don't chip away a damaged section) before the expert's inspection, if you can avoid it — it's your primary piece of evidence.
• Ask the expert directly whether the defect could have arisen at design stage or only during execution — that question shapes everything that follows.

The expert's opinion doesn't settle the matter legally, but in practice it's what decides who you pursue first, and how strong your negotiating position is.

Documents and evidence to gather

Common mistakes

• Going straight for the subcontractor, when you have no contract with them — this usually drags the case out rather than speeding it up.
• No independent expert's report before sending a letter — without establishing the cause, it's hard to identify the right party to pursue.
• Removing evidence of the defect (e.g. a quick fix-up job) before documenting the state of things — this makes proving the case later much harder.
• Confusing the site manager's professional liability with civil liability — reporting them to the Chamber of Civil Engineers doesn't replace a compensation claim.
• Not acting on entries in the site log during the works — if something raised concerns, it was worth flagging in writing at the time.
• Assuming the designer is liable for everything because they signed off the design — their liability covers design defects only, not the quality of the workmanship.

Step-by-step: what to do

1. Preserve the evidence of the defect — photos, video, a description and the date it appeared, without interfering with its state.
2. Pull together the site paperwork — the contract, site log/diary, design, handover reports, correspondence.
3. Commission an independent building expert's report, if the defect is serious or its cause isn't obvious.
4. Use the expert's findings to establish whether it's a design defect, a workmanship defect, or a supervision failure.
5. Send a written notice of the defect to the main contractor — with a description, photographic evidence, and a demand, e.g. to fix the defect within a set deadline.
6. If the expert's report clearly points to a design error, consider notifying the designer in parallel.
7. Consider taking legal advice before going to court — especially where several parties are involved and liability is disputed.

Time limits and limitation periods

The applicable time limits depend on the basis of the claim and the type of contract, so they need to be worked out for your specific case:

• Claims under a specific-task contract (umowa o dzieło — this often also covers design contracts) are generally time-barred 2 years after the work is handed over.
• Where the contract qualifies as a building-works contract, the general limitation periods apply — 6 years, or 3 years for claims connected with a business activity.
• The statutory warranty for defects in a building (rękojmia) has its own, longer time limit — 5 years.
• Tort claims (e.g. against a subcontractor acting outside any contract) are time-barred under separate rules — generally 3 years from finding out about the damage and the person liable, but no later than 10 years from the event.

Because several different bases of liability (contract, tort, statutory warranty) often overlap in this type of case, working out the correct limitation period for your specific matter needs a lawyer's assessment — getting the legal classification wrong can cost you the claim altogether.

Frequently asked questions

Can I sue the subcontractor directly, bypassing the main contractor? It's generally harder — you have no contract with them, so the basis for your claim is weaker, unless they caused damage in a way that's independent of any contract. It's usually more straightforward and effective to direct your claim at the main contractor, who's liable for the whole job, including what its subcontractors did.

Is the site manager personally liable for defects, out of their own pocket? They can be, if the defect stems from their own supervisory failings and there's an appropriate legal basis linking them to you — but that requires showing a link between their conduct and the damage. In practice, their professional indemnity insurance is often what actually pays out.

How do I tell a design defect apart from a workmanship defect? Without specialist knowledge, you generally can't — which is why an independent building expert's report is essential. The surveyor compares what was built against the design and identifies the stage at which the fault arose.

Will reporting the matter to the Chamber of Civil Engineers get me compensation? Not directly — that's a professional disciplinary process, which might end in, say, a reprimand or a ban on carrying out the role, not a civil claim for your loss. Compensation has to be pursued separately.

What if the main contractor has disappeared or gone insolvent? That's when direct claims against the subcontractor, the site manager or the designer become more important, as they may be your only realistic route — but each of those bases needs its own legal analysis as to whether it even exists and how to prove it.

Legal basis

This guide draws on the provisions of the Polish Civil Code on specific-task contracts, building-works contracts, liability for the people a debtor uses to perform an obligation, and torts — including Articles 415, 442¹, 471, 474, 568, 627 et seq., 646, and 647 et seq. of the Act of 23 April 1964 – Civil Code (consolidated text: Dz.U. 2026 poz. 795), as well as the provisions of the Act of 7 July 1994 – Construction Law on the duties and liability of the site manager and the designer. The "" markers flag statements whose current wording, numbering and application to a specific set of facts should be confirmed by a lawyer before publication — this category of case, involving several parties' liability at once, is one of the trickier ones to classify.

Related guides

• Building or renovation work damaged a neighbour's property in Poland — who is liable? — when a workmanship defect affected a neighbour rather than you.
• Flooding During Renovation Work in Poland — Who Is Liable, and How Do You Claim? — a specific scenario of damage arising from a workmanship error.
• Building Contractor Did a Bad Job in Poland — How to Start a Defects Claim — general claims against a contractor.
• Builder Won't Fix Defects in Poland? How to Send a Formal Demand Letter — when the contractor refuses to remedy a defect.
• All guides on disputes with businesses (in Polish) — the full topic hub.

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