A few centimetres too much or too little may sound harmless - but in tenancy law they can quickly add up to four to five-figure sums. Whether ancillary costs, rent increases or the marketing of a flat: the correct living space is the linchpin. If you work properly here, you can avoid disputes, additional payments and damage to your image. In the following, you will find out why area deviations are so critical, which standards apply, how to carry out a quick plausibility check and which mistakes can be elegantly avoided.

Why a few centimetres can now prove costly

Living space is more than just a figure in the property brochure – it forms the basis for rent, service charges and rent increases. Even small variations affect several items at once and add up over the course of a tenancy.

What exactly is „living space“ – and what rules apply?

In tenancy law, the living space is predominantly determined by the Living Space Ordinance (WoFlV) calculated. It differentiates strictly according to the usability of the areas: Rooms with Sloping roofs Those with a headroom of 2.00 m or more count as 100 %, those between 1.00 and 2.00 m count as 50 %, and those below 1.00 m do not count at all. Balconies, loggias and terraces are generally calculated at a rate of 25 % to 50 % (depending on the individual case, based on location and quality). Cellars, boiler rooms and garages do not count as living space.

In addition, there is the DIN 277, which is frequently used for project development, new-build projects and commercial properties. It takes account of gross floor areas and usable floor areas, and regularly results in higher figures than the WoFlV. For Rented flats However, the WoFlV usually takes precedence – unless otherwise agreed in the contract. This is precisely where discrepancies arise: if a property is marketed in accordance with DIN 277 but billed in accordance with the WoFlV, this gives rise to a conflict.

Legal framework: The Federal Court of Justice’s 10 % rule

The case law (BGH) has a clear guard rail: If the actual living space differs by more than 10 % from the living space agreed in the contract, this constitutes a defect. This also applies to „approx.“ figures. The consequences:

• Rent reduction in the amount of the percentage deviation is permissible.
• Reclaim overpaid rent (regularly up to 3 years retrospectively, note limitation periods).
• Ancillary costs and Rent increases (index/rental index) may be based on an incorrect area - with risks of reversal.

Landlords and property managers are therefore obliged to provide reliable documentation of floor space details. On the tenant side, a factual check is worthwhile, especially for sloping ceilings, conservatories and balconies.

Concrete calculation examples: When will it be expensive?

Effects on ancillary costs, index-linked rent and rent index

The living space influences the Distribution of operating costs (e.g. council tax, cleaning, management – depending on the agreement). An excessively large floor area regularly leads to excessive service charges. Also Index-linked rent and Rent increase according to rent index are based on the living area; if this figure is incorrect, requests for an increase can be challenged. For owners, this means that those who correct their figures now will avoid costly adjustments and legal disputes in the future.

Practical tips for landlords and tenants

• Clear reference standard: Explicitly refer to the „Living Space Regulation (WoFlV)“ in the tenancy agreement, where applicable.
• Check documents: Floor plan, declaration of division, measurement protocol; in the case of old buildings, pay attention to slopes and recesses.
• Professional measurement: If in doubt or in the event of alterations, have an up-to-date, legally compliant survey carried out.
• Property brochure = contract: The figures in the property brochure must match the area specified in the contract; otherwise, there is a risk of a loss of trust and liability.
• Adjust operating costs: Once the area has been corrected, update the allocation keys on an ongoing basis.
• Communication: Explain deviations openly, explain the calculation method - this defuses conflicts.

Marketing and returns: precision as a competitive advantage

Precise surfaces are not an end in themselves, but make good business sense. They create Traceability and prevent objections in the later contractual phase. For sellers, a reliable land survey increases the Transparency and thus the speed of marketing. For landlords, the risk of subsequent claims and reversals is reduced. And: a correct area basis allows legitimate rent increases to be enforced safely - without a target.

Conclusion: Differences in floor area are not a minor detail – they determine rent reductions, back payments and the legal stability of your tenancies. Anyone who applies the WoFlV, measures accurately and documents clearly is acting in a financially prudent manner and minimising risks. We would be happy to review your documents, coordinate a survey and manage communication with tenants – quickly, accurately and discreetly. Book an appointment here for a no-obligation initial consultation.

Your contact at FLEXMAKLER Robert Schüßler Offers personalised advice on living space, valuation and marketing.