Why the burden of proof decides construction disputes
In a German construction case the burden of proof bites at two moments — and both hurt.
First: the advance on the expert’s fees. A defect dispute almost always requires an opinion from a court-appointed expert. The court demands the advance on those costs from the party that has to prove the fact in question and applies for the expert evidence. On larger projects this means thousands, sometimes tens of thousands of euros — payable up front, long before any judgment.
Second: the stalemate (non liquet). If, after all the evidence has been taken, it cannot be established whether a defect existed, the party bearing the burden of proof loses. As long as the defect is still on site and the expert can inspect it, such a stalemate is rare. Everything changes once the defects have been repaired without proper documentation or the building has been altered — then the winner is not the party that is right, but the party that did not have to prove anything.
Two different questions: what was agreed and what was built
A “defect” under German contract law for works and construction is a gap between the agreed state and the delivered state. Courts examine this in two steps. First they establish what the contractor actually undertook to do — which scope, which quality, which function. Only then do they compare whether the actual execution matches it.
For the burden of proof this distinction is crucial, because the content of the contract and the correctness of the execution follow separate rules. In practice, orders for the taking of evidence sometimes blur the two levels — so it pays to check, as early as the evidentiary stage, what exactly the court is asking the expert and which party carries that particular burden.
Acceptance (Abnahme) — the turning point of the whole dispute
The pivot of the burden of proof is the acceptance of the works (§ 640 BGB). The logic of the Civil Code is simple. Whoever claims to have performed the contract must prove it (§ 362 BGB). But whoever has accepted a performance as fulfilment must, in a dispute, prove that what he received was different or incomplete (§ 363 BGB). Acceptance of construction works is precisely such an approval of the performance.
Before acceptance, the contractor bears the burden of proving that the works comply with the contract. That applies to his own claims — for acceptance and for payment — as well as to his defence against the principal’s demands.
After acceptance, the roles reverse: the principal must prove that the works fall short of the contract. It makes no difference whether he is defending against the final invoice or pursuing defect claims himself. The case law goes one step further: by accepting the works the principal approves not only the execution but also the yardstick against which it is measured — after acceptance he must therefore also prove any disputed contract terms he relies on.
One important exception favours the principal even after acceptance: if the contractor claims to have repaired notified, undisputed defects, it is the contractor who must prove that the repair was successful — until the principal accepts the rework as performance.
What was agreed — where most cases are lost
Oral contracts. Genuine disputes about the content of the contract mostly arise where the deal was made orally or by quick e-mails. Before acceptance the general rule applies: each party proves the terms from which it derives favourable consequences. The contractor claiming payment — the agreed scope and standard. The principal claiming that more or better was agreed — exactly that “more”. Whoever asserts that particular documents (an offer, a specification, drawings) became part of the contract must prove it.
Written contracts. Where the contract is in writing, its content is determined primarily by interpretation, and the documents enjoy a presumption of completeness and correctness. Whoever claims that something further was agreed outside the document must prove it.
Later changes. Changes to scope, standard or method are always proved by the party relying on them — regardless of whether acceptance has taken place. Hence the iron rule of site practice: confirm every change, even with a short e-mail.
“That is what we agreed, it was meant to be cheaper” — agreeing a lower standard. This is the classic contractor defence: the execution falls short of the usual quality because a simpler standard was agreed for that price. German case law sets the bar high. First, the contractor implicitly promises the principal compliance with the recognised rules of technology (allgemein anerkannte Regeln der Technik) and the achievement of the function the works are meant to serve — the so-called functional concept of defect, settled since the judgment of the Federal Court of Justice of 8 November 2007 (VII ZR 183/05). If the agreed or presumed function is not achieved, the works are defective even where the contractor did exactly what the contract text says. He then escapes liability only by showing that he fulfilled his duties to examine and to warn — more on this in our article on the Bedenkenanmeldung, the contractor’s notice of concerns.
Second, where the function is achieved but the execution falls below the recognised technical rules or the quality typical of comparable buildings, a lower standard is validly agreed only if the contractor — as the professional — made the principal clearly aware of the risks involved. And it is the contractor who must prove that he gave this warning or that it was unnecessary. Acceptance changes nothing here. The argument that at a low price the principal could not expect decent quality is consistently rejected by the courts.
Defect claims before acceptance — settling up after the cooperation collapses
As a rule the principal can invoke the defect remedies of § 634 BGB only after acceptance — so the Federal Court of Justice in its judgment of 19 January 2017 (VII ZR 301/13). The exception: the cooperation has definitively ended and the contract has turned into a pure settlement relationship (Abrechnungsverhältnis) — the principal finally no longer wants performance from this contractor and the parties settle what has been built. This is the frequent endgame of disputes around the final invoice (Schlussrechnung).
Who proves the defects in such a settlement? Since there has been no acceptance, the courts stick to the principle: the contractor must show that his works complied with the contract — even where it is the principal who asserts defect claims. Legal writing increasingly argues that in this constellation the burden should lie with the principal, but the courts have so far not taken that path. For the contractor this means in practice: in a settlement dispute, merely denying the allegations is not enough — you must be able to positively demonstrate the quality of your own works.
The biggest evidentiary trap: defects repaired by another company
The typical scenario: the principal sets a deadline for rectification, the deadline passes, a third company carries out the repairs (Ersatzvornahme, § 637 BGB) and the contractor receives the bill. The problem: the defect no longer exists — the expert has nothing to inspect and the dispute heads straight for a stalemate.
The Federal Court of Justice resolved this dilemma in its judgment of 23 October 2008 (VII ZR 64/07): if there has been no acceptance, the burden of proving proper performance remains with the contractor even after the disputed works have been removed. The contractor is not defenceless, though. He is protected by the doctrine of frustration of evidence (Beweisvereitelung): whoever culpably deprives the opponent of the possibility of proving his case — for instance by discarding the removed components, rebuilding the disputed section without any documentation, or shutting the contractor out of the repairs despite his request to attend — must expect the court to grant the opponent evidentiary relief, up to and including a full reversal of the burden of proof.
This translates into concrete precautions for both sides.
The principal should, before any repairs, give the contractor the chance to inspect, document the state of the works with photographs and a protocol, preserve the replaced components and, where larger sums are at stake, consider independent judicial preservation of evidence (selbständiges Beweisverfahren, § 485 ZPO) — a court-appointed expert then records the condition before the repair, and the findings can be used in the later lawsuit.
The contractor should never ignore a notice of defects (Mängelrüge), even if he considers it unfounded: use the opportunity to inspect the alleged defect on site, document it himself and, above all, demand in writing to be involved in any rectification works. That letter later becomes the strongest foundation of a frustration-of-evidence objection.
A defect dispute is looming — what to secure right away
Photograph every stage of the works that will later disappear under the next layer. Keep partial protocols, measurements and all correspondence about changes of scope. Defect notices and replies — in writing only. Before any defect is repaired: joint inspection, documentation, preservation of replaced components and, if needed, judicial preservation of evidence. After completion: a formal request for acceptance with a deadline. Each of these steps costs little — omitting them can cost the entire case.
Acceptance under reservation and deemed acceptance
Reserving defects at acceptance. Whoever accepts the works knowing of a specific defect should reserve it at acceptance — otherwise he loses the claims for rectification, self-remedy, rescission and price reduction and is left, in principle, only with damages (§ 640(3) BGB). An effective reservation also has an evidentiary effect: for the reserved defects the burden of proof does not pass to the principal but stays with the contractor, because in that respect the performance was precisely not approved.
Deemed acceptance under § 640(2) BGB. If the contractor, after completion, sets the principal a reasonable deadline for acceptance and the principal does not refuse within that deadline stating at least one defect, the works are deemed accepted. Vis-à-vis consumers the fiction only works if the contractor pointed out the consequences of silence in text form. According to the prevailing view this fiction triggers the full effects of acceptance — including the shift of the burden of proof to the principal. Staying silent in the face of a request for acceptance is therefore dangerous for the principal, while for the contractor a dated request for acceptance is one of the cheapest tools to improve his own position.
Deemed acceptance under § 12(5) VOB/B. Where the VOB/B applies, acceptance is deemed to occur 12 working days after notice of completion or 6 working days after the principal starts using the works. Whether these fictions also shift the burden of proof is disputed — there are strong arguments against, since the mere lapse of a deadline hardly expresses approval of the works as performance. A litigation strategy should not be built on the VOB/B fictions.
Refused acceptance and the joint record of condition. If the principal refuses acceptance, the contractor can, under a construction contract, demand a joint determination of the state of the works (Zustandsfeststellung, § 650g BGB). An obvious defect not noted in that record is later, in case of doubt, deemed to have arisen after the record was drawn up. The tool only covers visible defects, though — it does not solve hidden problems.
What this means for your company
- Until acceptance you are playing under your own burden of proof. Document the execution as you go: photos of each stage, measurements, partial protocols, a site diary. This is your future trial material, not red tape.
- Push for a formal acceptance. The acceptance protocol is the most valuable document of the whole project — it decides who proves defects afterwards. If the principal stalls, set a deadline for acceptance and use the fiction of § 640(2) BGB.
- React to defect notices immediately. Inspect, document, demand in writing to attend the repairs. Ignoring a Mängelrüge hands the opponent control over the evidence.
- Changes in writing only. A casual “just add this as well” is proved by whoever relies on it — an e-mail sent the same day solves the problem.
- A lower standard requires a warning. A cheaper method at the principal’s request is fine, but the risks must be spelled out in writing — otherwise there will be no proof at trial that the principal knew what he agreed to.
Frequently asked questions
Who pays for the expert in a construction defect dispute?
The court collects the advance on the expert’s fees from the party that has to prove the fact in question and applies for the evidence. The losing party ultimately bears the costs of the case — but the advance must be paid up front, which on larger projects can be a real barrier.
There is no acceptance protocol. Does that mean there was no acceptance?
Not necessarily. Acceptance can also take place through conduct — for example by paying the final invoice and using the building without complaints for a longer period. Whether such conduct was sufficient depends on the circumstances. A protocol remains the safest proof and the reference point for deadlines.
The principal had the alleged defects repaired by another company and demands the costs. Does he have to prove the defects existed?
If the works were never accepted, it is in principle the contractor who must prove proper performance — even where the disputed section no longer exists. But if the principal removed the defects without documentation and without letting the contractor inspect, despite a request, the doctrine of frustration of evidence applies — with evidentiary relief for the contractor up to a reversal of the burden of proof. After acceptance the burden of proving defects lies with the principal anyway.
Does the VOB/B change the burden of proof?
The core stays the same: before acceptance the contractor proves, after acceptance the principal. What is disputed is whether the deemed-acceptance rules of § 12(5) VOB/B shift the burden of proof — so it is safer to treat them as triggering deadlines only, not as an evidentiary shield.
What does a selbständiges Beweisverfahren achieve?
It is a judicial procedure for preserving evidence: a court-appointed expert documents the state of the works before defects are repaired or covered up. The findings can be used in the later lawsuit as if the evidence had been taken by the trial court. For the principal it is the safest route before commissioning repairs from a third company, for the contractor a way to record the quality of his works when a dispute is brewing.
This overview draws, among others, on the judgments of the Federal Court of Justice of 8 November 2007 (VII ZR 183/05), of 23 October 2008 (VII ZR 64/07) and of 19 January 2017 (VII ZR 301/13) as well as §§ 362, 363, 634, 637, 640 and 650g BGB, § 12(5) VOB/B and § 485 ZPO. This article is for information purposes and does not replace legal advice in an individual case.