Checking a Prefab House Build Specification: Minimum Details, Gaps and Checklist

The building specification (Baubeschreibung) is the decisive document when buying a prefabricated house – more significant than any glossy brochure. It records which services are contained in the price, and everything missing from it is charged additionally later. Anyone who wants to check a prefabricated house building specification should know the statutory minimum requirements under Article 249 EGBGB, compare the scope of services of several providers and specifically track down the typical gaps. This guide provides you with a systematic checklist for this – and shows where you can obtain an independent review. Anyone who wants to build turnkey should pay particular attention in the building specification to the scope of the interior finishing trades.

Minimum requirements under Art. 249 EGBGB

Important: the statutory requirement prescribes that a description must be given – not how high-quality the construction is. A provider fulfils Art. 249 EGBGB even with a cheap standard, as long as it describes it clearly. The building specification is therefore above all a transparency promise, not a quality promise. This is precisely the most common fallacy when buying a prefabricated house: many prospective buyers equate a detailed, professional-looking building specification with high construction quality. In fact, the scope of the document initially only says something about the care of the description. Whether the described standard suits your demands you have to judge yourself, position by position – or have judged. This information must be contained at a minimum in 2026:

• General description of the building to be erected with floor plan, living space and room layout.
• Type and scope of the offered services as well as explicitly excluded services.
• Building data, plans and information on the construction and building physics.
• Description of the interior finishing and the building services (heating, sanitary, electrics, ventilation).
• Information on the energy, fire protection and sound insulation standard.
• Binding information on the completion date.

For the formal framework of the contract itself – withdrawal, payment plan, 90 % limit – read in addition the guide checking the prefabricated house contract as well as the general basics under checking the construction contract. Where the building specification stands in the entire purchase process is shown by the guide buying a prefabricated house.

A second aspect is often overlooked: the building specification becomes part of the contract. What is stated in it, the company owes – and only that. Brochures, show house impressions or verbal promises from the salesperson are legally worthless as long as they are not incorporated into the building specification or the contract. Therefore insist that every verbally promised service is taken over into the building specification in writing. An older, generally worded building specification that pushes many details into the later "measurement" (Aufmaß) or the "fittings selection" (Bemusterung) shifts the cost risk onto you – with a transparently worded specification, on the other hand, quantities, qualities and makes are already fixed.

Comparing the scope of services: why identical framework conditions count

A common mistake is comparing final prices without looking at the scope of services. The cheaper provider can become more expensive as soon as you buy the missing items additionally. Therefore compare in a structured way:

Set up a simple table for the comparison: the trades are in the rows, the providers in the columns. This way you recognise at a glance where one provider lists an item as included that another marks as "on the builder's side" (bauseits) or "optional". Only this row-by-row reconciliation makes the final prices honestly comparable – and exposes seemingly cheap offers that are bought at the price of missing services. Pay particular attention to items that do not appear at all in one offer: what is not mentioned is usually also not calculated.

Via our manufacturer comparison and the house catalogues you can request building specifications from several companies and lay them side by side. We compare verifiable characteristics – without a ranking, without a test winner.

Typical gaps: earthworks, house connections, painting work

Comb through the building specification specifically for the words "on the builder's side" (bauseits), "not included", "optional" and "according to expenditure". At these points the later additional demands hide. The most common gaps in 2026:

Fittings selection: when the standard becomes a cost trap

Therefore demand that the building specification contains a fitting schedule of services with concrete makes, price groups and quantities – sockets per room, tile area, sanitary fixtures, interior doors. The contractual side of the fittings selection we cover in depth in the guide checking the prefabricated house contract. Pay attention to:

• Concrete makes and price groups instead of “standard selection”.
• Quantities: sockets and switches per room, number of bathrooms, interior doors.
• Tile area and quality, floor covering per room type.
• Sanitary fixtures including fittings with manufacturer details.
• Rule on whether unused fittings-selection budget is forfeited.

Reading the energy standard and building services correctly

Especially with a prefabricated house in timber construction, airtightness is a central quality feature. Check whether a blower door test is agreed and which target value should apply. With the heating system, the building specification should not merely name "heat pump", but the make, output, storage size and whether a photovoltaic system is provided for or only prepared. This information can hardly be renegotiated later without additional costs arising:

• U-values for external wall, roof, floor slab and windows – as concrete figures.
• Achieved efficiency house standard (e.g. EH 55/40) instead of only “GEG-compliant”.
• Heating system with make, output, storage and heating surfaces (underfloor heating).
• Ventilation: controlled residential ventilation with heat recovery – yes/no.
• Airtightness: blower door test agreed, target value named.
• Photovoltaics and storage: included, only prepared or not provided for.
• Electrics: number of sockets and circuits per room, pre-fitting for an electric car.

How the execution of this technology is later monitored on the construction site is described by the guide prefabricated house construction supervision. Because a good building specification is only useful if the company also implements the promised quality.

Having the building specification checked independently

An independent review is particularly valuable precisely with the building specification, because laypeople often overlook the decisive omissions: a missing trade is less noticeable than a badly worded paragraph. An experienced expert, on the other hand, reads the specification against a reference list of complete trades and marks exactly the points where later addenda threaten. In 2026, reckon with around 250 to 800 euros for a building-specification review – a small investment measured against additional demands in the five-figure range.

A professional review uncovers gaps, unclear wording and missing quantity details before you sign. Neutral points of contact are the Association of Private Builders (Verband Privater Bauherren), the Builders' Protection Association (Bauherren-Schutzbund) and the IHK expert directory. An accompanying inspection of the entire construction we cover in the guide prefabricated house construction supervision, the quality inspection in detail under prefabricated house quality control.

Checklist: checking the prefabricated house building specification point by point

• Mandatory content under Art. 249 EGBGB fully present.
• Finishing level clearly named (turnkey, ready-for-services, finishing-stage house).
• Wall structure, U-values, insulation thicknesses and energy standard specified.
• Heating, ventilation, sanitary and electrics with makes and quantities.
• Fittings-selection budget per trade with price groups and quantities.
• All “on the builder's side” and “optional” items listed and quantified.
• Binding information on the completion date included.
• Independent review by VPB, BSB or an expert before signing.

Once the building specification has been checked and the contract signed, the inspection of the execution follows. How to recognise and document defects early you can read in the guide prefabricated house defect inspection and – for the legally secure handover – under prefabricated house building acceptance.