Checking a Prefab House Contract: the Prefab-Typical Traps in the Contract

A prefabricated house contract is not an everyday construction contract: anyone who wants to check the contract for a prefabricated house should look less at the general German Civil Code (BGB) basics – these apply to every new build – and more at the peculiarities typical of prefabricated houses. The sample selection (Bemusterung), price escalation clauses, the delimitation of the fit-out stage, the works-contract payment plan and the delivery time ex-works decide here over tens of thousands of euros and months of construction time. This guide shows which clauses in the prefabricated house contract are particularly critical in 2026, what an independent contract review pays attention to and where you find neutral experts.

Why a prefabricated house contract is checked differently from a solid-build contract

Legally, the prefabricated house contract is, for private builders, usually a consumer construction contract under § 650i BGB, provided the company takes on the construction of a new house “from a single source”. This means all consumer protection rights apply – from the 14-day right of withdrawal, through the obligation to provide a building specification, to the limitation of instalment payments. The actual review of a prefabricated house contract, however, revolves around the points that follow from the works production. Anyone who systematically goes through these five areas exposes the economically significant risks.

Sample selection: the costliest contract trap in the prefabricated house contract

Many builders sign the contract long before the sample-selection appointment – often because only the contract sets the financing in motion. Precisely therein lies the risk: what stands in the contract as “high-quality equipment according to the show home” is legally hard to grasp. Only at the sample-selection table does it turn out that the selection included in the fixed price is narrow and sought-after tiles, parquet or sanitary ranges slip into a more expensive price group. In the contract, therefore, pay attention to:

• A specifically quantified sample-selection budget per trade (tiles, floors, sanitary, doors, electrical) instead of vague wording.
• A reference to the building specification with named makes and price groups – for this, read the guide Checking the prefabricated house building specification.
• The rule on whether unused budget is credited or lapses (usually it lapses).
• A binding sample-selection appointment BEFORE conclusion of the contract or a right of withdrawal should the sample selection significantly exceed the budget.
• Surcharge-liable special wishes with a comprehensible price list instead of open recalculation.

We explain gaps in services and minimum details extensively in the guide Checking the prefabricated house building specification. Building specification and sample selection belong together: the building specification determines the standard, the sample selection implements it – and deviations cost money.

Check price commitment and price escalation clauses correctly

Pay attention above all to the connection between the fixed-price duration and the assembly date: if the guaranteed assembly date falls outside the fixed-price commitment, the “fixed price” is hardly worth anything. Have the commitment extended so that it includes the contractually promised assembly date with a buffer. How the total costs of a new build in 2026 are composed is shown by our overview of the house-building costs.

Clearly delimit the fit-out stage in the contract

Check in the contract whether a complete list of trades with a clear “company/builder” assignment exists. Grey areas often open up at the transitions: who plasters the walls, who paints them, who lays the screed, who lays the floor covering? Who fits the internal doors, who connects the lamps? Without a clear assignment, you later argue over additional invoices and responsibilities. Common points of conflict:

Payment plan under the MaBV and BGB: when which instalment is due

With the prefabricated house, the payment plan is particularly tricky because a large part of the service is created in the works before anything visible happens on the building site. Some contracts therefore demand a high instalment “at the start of works production”. Check whether this advance performance is secured by a security under § 650m BGB – with consumer construction contracts, that is 5 percent of the remuneration as protection against defects and insolvency. Pay attention to:

• The instalment amount is based on the actual construction progress, not on calendar dates.
• No instalment beyond the value provided – advance payment is a warning signal.
• Insolvency protection / contract performance guarantee for advance performances of the works production.
• 5-percent security under § 650m BGB with consumer construction contracts.
• The final instalment only after defect-free acceptance – hold back 10 percent until then.

Pin down the delivery time and assembly date bindingly

Demand a delay clause with lump-sum compensation – for example €80 to €120 per day of delay as compensation for rental costs. Just as important is the coupling of the assembly date and the fixed-price commitment (see above). Also check which “force majeure” releases the company from the deadline; broadly drawn clauses hollow out every date commitment. How production, permit and assembly fit into the entire schedule is shown by the house-building process guide. Where the contract review stands in the entire purchase process is shown by the guide Buying a prefabricated house.

Having the prefabricated house contract checked independently: who to turn to?

In 2026, an independent review costs, depending on the scope, usually €250 to €900 – a manageable expense in relation to the construction sum and to possible additional demands at the sample selection. Neutral points of contact are:

• Verband Privater Bauherren (VPB) – nationwide advice offices for contract and construction consultation.
• Bauherren-Schutzbund (BSB) e. V. – contract review and construction-accompanying consultation.
• Specialist lawyer for construction and architects’ law – for the purely legal review.
• Publicly appointed and sworn (ö.b.u.v.) experts via the IHK expert directory.
• The Verbraucherzentrale (consumer advice centre) of your federal state – for an initial orientation on construction contracts.

Neutral contact points can be found at the Verband Privater Bauherren, at the Bauherren-Schutzbund as well as in the IHK expert directory. The accompanying control of the construction itself we cover in the guide Prefabricated house construction supervision – the central overview around the independent control of your prefabricated house construction. Anyone who wants to keep an especially close eye on costs and extra items will find notes in the guide Prefabricated house construction controlling.

Checklist: check the prefabricated house contract point by point

• Sample-selection budget quantified per trade and linked to the building specification.
• The fixed-price commitment covers the promised assembly date with a buffer.
• A price-index clause is missing or is capped at 3–5 %.
• Fit-out stage with a complete list of trades and a company/builder assignment.
• The payment plan follows the construction progress; advance performances are secured.
• 10 % final instalment only after defect-free acceptance; 5 % security under § 650m BGB.
• A binding assembly date with a delay clause (lump-sum compensation).
• An independent contract review by VPB, BSB or a specialist lawyer before signing.

To assess the construction quality during assembly, an additional look into the guides Prefabricated house quality control and Prefabricated house defect inspection is worthwhile. This way the arc closes from the contract review to the acceptance.