Reviewing a Construction Contract 2026: Works Contract, Consumer Building Contract and the Most Common Traps

The construction contract (Bauvertrag) is the most expensive document most people will ever sign – and, ironically, the one they engage with the least. Anyone building a prefabricated house (Fertighaus) in 2026 commits to six- or seven-figure sums, fixed payment schedules and deadlines that are almost impossible to correct once the ink is dry. Since construction contract law was introduced into the German Civil Code (BGB), private clients have enjoyed clear consumer protections – but only those who know their rights can actually claim them. This guide shows you which type of contract applies to your situation, which mandatory content belongs in a solid contract, where providers typically leave gaps – and when it genuinely pays off to consult a specialist lawyer or a client advisory service for roughly 200 to 400 euros. If you want to build turnkey (schlüsselfertig), you should scrutinise the scope of services in the contract especially carefully.

Work contract, construction contract or consumer construction contract – which applies to you?

The BGB construction contract law has several tiers, and the classification determines which rights you are entitled to. The work contract (Werkvertrag, § 631 BGB) forms the basis of every construction service: you owe money, the company owes a defect-free result. The construction contract (§ 650a) is a special work contract for the erection, restoration or conversion of a building. The consumer construction contract (§ 650i), in turn, is a special case of the construction contract – it applies when a consumer commissions a company to build a new building or carry out substantial conversion work. This is exactly where the turnkey prefabricated house belongs.

This distinction is no legal hair-splitting; it has concrete consequences for your money: only the consumer construction contract obliges the provider to supply a detailed construction description, a binding deadline and the right of withdrawal, and it caps the instalment payments. If a client instead awards the trades individually to different craftspeople, many separate contracts arise without this protection. Anyone wanting to avoid that risk is usually better positioned with a general contractor and a solid consumer construction contract. For how the construction methods differ in price, see the overview of house building costs. Before you even negotiate a contract, it is worth looking at the experiences of other clients with the respective provider – and at our checklist for comparing providers.

Mandatory content: what a consumer construction contract must include

The construction description is the centrepiece – it is regulated by law in Art. 249 § 2 EGBGB and must set out the essential characteristics of the house clearly and comprehensibly. This includes the type and scope of services, the building data, the construction of all essential trades, the standards of interior fit-out and building technology, the energy standard and the sanitary installations. Vague wording such as “high-quality brand products” without specific makes, quantities or quality levels is a warning sign: whatever is not precisely described will, in case of doubt, be supplied in the cheapest permissible version.

Payment plan and the 90 percent cap

With consumer construction contracts, the total instalment payments must not exceed 90 percent of the agreed overall remuneration under § 650m BGB – the remaining minimum of 10 percent only falls due upon acceptance. This protects you from having already fully paid for an almost finished house in the event of delay or the provider's insolvency. In addition, with the first instalment, the company must provide you with security amounting to five percent of the remuneration – for example, as a guarantee for on-time, defect-free completion.

A sound payment plan is based on the construction services actually rendered, not on rigid calendar dates. If a contract demands high advance payments before any building has even started, or if the sum of the rates before acceptance exceeds the 90 percent cap, the clause is invalid – and a clear signal to have the contract examined more thoroughly. For how the acceptance process has legal effects, read the guide to building acceptance & warranty.

Right of withdrawal: using the 14-day cooling-off period wisely

The right of withdrawal is not a free pass, but a valuable safety valve. Anyone who signed under the pressure of a sales pitch gains two weeks of genuine reflection time – enough to have the contract examined by an independent client advisory service. Important: the right of withdrawal relates to the construction contract with the company, not to the notarised land purchase contract, for which separate rules apply. If you withdraw, you may only be charged for the services actually rendered up to that point – provided the instruction was correct.

Common pitfalls in the construction contract – and how to spot them

Particularly treacherous is the flat-rate price gap: the brochure lures you with an attractive fixed price, yet in the fine print items appear as “to be provided by the client” or “not included in the scope of supply”. Classic examples are earthworks and excavation, the foundation slab or cellar, utility connections, the site access road, the soil survey, outdoor facilities, painting and floor coverings. What comes across as a cheap starting price quickly grows by 15 to 30 percent through such supplementary items and extra costs. Therefore, insist on a comparison based on identical services – only then are two offers even comparable. For how to decode a prefab price list item by item, see our dedicated guide.

Equally important is a robust construction-period provision. Without a binding completion date, you bear the risk of double costs from rent and loan interest if a delay occurs. A good contract names either a fixed date or a fixed construction period from a clearly defined starting event and regulates what happens if it is exceeded. For how realistic the time estimates are, the guide to prefab construction time provides context. For which rights you have in the event of a construction delay, we explain separately.

Contractual penalties and price adjustment clauses

Contractual penalties for exceeding the construction period are generally permissible but must remain proportionate – typical guideline values are around 0.2 to 0.3 percent of the contract sum per working day of delay, capped at around 5 percent of the total. If such a clause is missing entirely, in the event of delay you are left with the more laborious route via concrete proof of damage. Conversely, unilateral price escalation clauses that allow the provider to make arbitrary additional claims for material or labour costs are critical: a genuine fixed price should guarantee the price for a defined period – often twelve months from conclusion of the contract.

Reviewing the construction description: the devil is in the standard

Pay particular attention to the quantity schedules: how many power outlets, switches and light outlets are provided per room? What tile prices are set per square metre, and from what value do you pay extra? Is the heat pump calculated including connection and buffer storage? Is a photovoltaic system included if the development plan (Bebauungsplan) requires it? Such details are anything but a side issue – added together, they often make the difference between a realistic and an embellished offer. Whether a cellar is sensible and how it is calculated is covered by the guide to prefab houses with a cellar. A structured step-by-step guide to uncovering gaps and vague wording can be found in the guide to reviewing the construction description.

Also check whether the construction description matches the requirements of your building permit (Baugenehmigung). Stipulations from the development plan concerning roof shape, heights or a solar obligation must be reflected in the agreed scope of services. Whatever is missing here will later be added as a chargeable supplementary item. Background on this is provided by the guides on assessing a plot of land and on the building permit for a prefab house.

Securities, guarantees and protection in the event of insolvency

The 90 percent cap and the completion security are the two most important protective mechanisms against one of the biggest nightmares in house building: the insolvency of the construction company with the shell half finished. If a maximum of 90 percent has been paid and five percent is secured, you retain financial leeway to continue building with another company. Therefore check whether the guarantee comes from a bank or a credit insurer and whether it is genuinely worded “on first demand” or at least irrevocably.

• A completion security of 5% is expressly agreed in the contract.
• The guarantee is handed over before or with the first instalment.
• The issuer of the guarantee is a bank or a credit insurer.
• The payment plan does not exceed 90% before acceptance.
• A written procedure is set out for special requests and supplementary items.
• The company's remuneration is clearly defined as a fixed price.

Review checklist: these 12 points before you sign

• The contract type is unambiguous – ideally a consumer construction contract under § 650i BGB.
• The construction description is complete, with specific makes, quantities and standards.
• A binding completion date or a fixed construction period from a starting event is named.
• The payment plan follows construction progress and does not exceed 90% before acceptance.
• The withdrawal instructions are provided in writing and are comprehensible.
• A completion security of 5% is agreed and evidenced by a guarantee.
• The fixed price applies for a defined period (e.g. 12 months from conclusion of the contract).
• A proportionate contractual penalty for exceeding the construction period is regulated.
• Special requests and supplementary items follow a written, price-transparent procedure.
• Foundation slab, earthworks and utility connections are clearly allocated – not left open as “client-provided”.
• Construction, builder's liability and fire-shell insurance are regulated.
• The contract was independently reviewed before signing (specialist lawyer / client advisory service).

When a specialist lawyer or client advisory service really pays off

Who should review depends on the concern. The consumer advice centres (Verbraucherzentralen) and independent client advisory services (such as association-backed offers) frequently review contracts and construction descriptions at fixed flat rates and provide both technical and commercial guidance. A specialist lawyer for construction and architectural law is the right address when complex clauses, unusual constructions or already foreseeable disputes are at stake. For the purely technical assessment of the construction description, a construction expert can also be helpful. For how a structured contract review proceeds step by step, see the guide to reviewing a prefab house contract.

Weigh the cost of the review against the risk: a single overlooked flat-rate price gap or a missing deadline can result in five-figure extra costs or months of trouble. The 200 to 400 euros for a well-founded initial assessment are therefore less an expense than an insurance policy. Firmly schedule the review into your timeline – ideally within the 14-day withdrawal period, so that you remain able to act in case of doubt. Particular caution is advisable with a prefab house from Poland, since warranty and contract law there can differ.

If a contract falls through or life circumstances change, you should know the consequences of ending it early. Which costs you will face and which statutes apply are explained by the guide Terminating a construction contract: §§ 648, 650l BGB and cost consequences.

Where the contract sits within the overall process is set out by the guide to buying a prefab house – from selecting the manufacturer to the final payment.