Square metre trap: How small deviations in area can trigger major rental disputes
Whether rent, ancillary costs or rent increases: in residential leases, the living space determines considerable sums. Even supposedly small deviations of a few per cent can change the legal situation and lead to lengthy disputes. If you know the rules for calculating living space and document them properly, you reduce your risk - and create the basis for fair, reliable tenancies.
Why every square metre counts
The monthly Rent is usually agreed as a price per square metre, as are Operating costs often distributed on the basis of an area key. The Federal Court of Justice (BGH) recognises an area deviation of more than 10 % as a rule as a significant defect. Consequence: Tenants can reduce the rent, reclaim overpayments and claim a refund based on an incorrect area. Rent increase attack. Conversely, landlords without reliable information on the floor area are in need of proof - especially in the case of old buildings, sloping ceilings or converted ancillary areas.
The most common causes of surface deviations
- Sloping ceilings: Areas under 2.00 m clear height are only partially counted; under 1.00 m not at all.
- Balconies, loggias, terraces: Usually count as 25 % according to the German Living Space Ordinance (WoFlV), up to 50 % for high-quality designs.
- Outdated floor plans: Plan dimensions often deviate from the actual use - especially after conversions.
- Wrong standard: WoFlV vs. DIN 277: In residential leases, the DIN 277 standard regularly applies. WoFlV, unless otherwise agreed. DIN 277 provides other results.
- Measurement error: Inaccurate devices, missing measuring points, slopes and recesses not correctly taken into account.
Legal situation short and clear
For living space, the Living Space Ordinance (WoFlV) unless otherwise stipulated in the contract. Key points: Areas with over 2.00 m Height counts in full, areas between 1.00 m and 2.00 m to 50 %, under 1.00 m not at all. Balconies, loggias, roof gardens and terraces are usually covered with 25 % for high-quality, year-round usable design up to 50 %. Storage rooms outside the flat (e.g. cellar) are not part of the living space. Conservatories count in full if they are heated and integrated into the flat.
It becomes legally critical from a Downward deviation of more than 10 % compared to the agreed living space. Then the rent is too high: tenants can minimise and if necessary. Repayments demand. Also Service charge settlements must be adjusted if the allocation formula uses the living space. Landlords should only justify rent increases on the basis of a reliably determined area - otherwise there is a risk of formal vulnerability and loss of trust.
Contract: 80 m², actual living space (WoFlV) measured: 72.5 m².
Deviation = (80 - 72.5) ÷ 80 = 9.4 %. Result: just under 10 % - legally no automatic reduction, but need for dialogue.
Second flat: Contract 80 m², measured 70 m² → deviation 12.5 %.
With a basic rent of € 1,200, € 150 per month would be too much. Over one year: € 1,800.
How landlords and tenants can avoid disputes
- standard in the contract: For living space, expressly agree „calculation according to WoFlV“, clearly document exceptions (e.g. balcony at 50 %).
- Measure professionally: Laser distance measurement and Measurement protocol with sketches, heights and balcony approaches. Commission a specialist office for complex floor plans.
- Evaluate slopes correctly: 1.00-2.00 m only 50 %; under 1.00 m 0 %. The error rate is particularly high in penthouses.
- Set balconies realistically: Standard 25 %, only with high-quality, weather-protected version 50 % - document!
- Ensure stock accuracy: Recheck surfaces after conversions, insulation, new floor structures or window replacements.
- Rent increase/utility costs: Check area basis before dispatch; incorrect square metres make increases vulnerable.
- Create transparency: The measurement report as an attachment to the rental agreement will help to avoid discussions at a later date.
Error 1: Basement, heating niches or outside storage rooms included → Solution: In accordance with the WoFlV, only state chargeable areas.
Error 2: Balcony valued at a flat rate of 50 % → Solution: Document quality (covering, alignment, weather protection). Otherwise apply 25 %.
Error 3: DIN 277 in the exposé, WoFlV in the tenancy agreement → Solution: Use a uniform standard and communicate clearly.
Error 4: Roof slopes counted in full → Solution: Measure the height separately and apply the 50 % rule.
Small deviation, big impact: what does that mean in figures?
Example: A flat is offered with 90 m², the correct WoFlV area is 81 m². This is a 10 % deviation. If the agreed basic rent is €1,350 (€15/m²), the authorised rent is 81 × €15 = €1,215. The difference of €135 per month adds up to €1,620 per year. In addition, the Service charge distribution key be checked if the apportionment is based on square metres - otherwise tenants pay disproportionately.
With under 10 % typically no automatic rent reduction can be enforced. Nevertheless, clarification is worthwhile: precise space details strengthen the market position, avoid queries and create trust - a value that pays off in lower fluctuation and faster lettings.
Best practice for landlords - with a view to reputation and returns
Professional market players treat living space like a key figure in the annual financial statements: tested, documented, resilient. A clear measurement protocol, transparent annex areas (balcony, terrace) and a standard clearly stated in the contract not only prevent disputes; they also speed up marketing and credit checks, because documents are accepted by banks and tenants without further enquiry.
Our recommendation: At the latest before a rent increase or new tenancy, check the area update. If you keep an eye on the 10 % hurdle and implement the WoFlV properly, you protect your yield - and provide tenants with the reliability they can expect.
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Conclusion: Square metres are not a numbers game, but a price factor with legal weight. Those who master standards, measurement and documentation avoid costly disputes - and gain the confidence to make big decisions in the property world.
