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Floor Area Discrepancy in a German Lease: The 10% Rule

Last updated: 27 August 2026 · Reading time approx. 9 minutes

"Anything below 10% is harmless" — that is the sentence you find everywhere about living area in German leases, and it is right about one case in three. The 10% threshold comes from a single line of cases: rent reduction. For rent increases and for service charge statements, the Federal Court of Justice (Bundesgerichtshof, BGH) has expressly abandoned any tolerance at all. There, the actual area governs — from the first square metre. This article covers what counts as living area under the German Wohnflächenverordnung, which consequence attaches to which threshold, and what an overstated figure in the lease costs over the years.

What counts as living area

The Wohnflächenverordnung (WoFlV, the German living-area regulation) works in two steps: § 2 WoFlV determines which rooms belong to the flat at all, and § 4 WoFlV determines the share at which their floor area is counted. Measuring is done, under § 3 (1) WoFlV, "nach den lichten Maßen zwischen den Bauteilen" — by the clear internal dimensions, taken from the front edge of the wall covering. Fixed installations, fitted furniture, radiators and skirting boards are expressly included by § 3 (2) WoFlV, so they do not reduce the area.

AreaCounted asProvision
Rooms and parts of rooms at least 2 metres in clear heightin full§ 4 No. 1 WoFlV
Parts of rooms from 1 metre up to under 2 metres (sloping ceilings)at half§ 4 No. 2 WoFlV
Unheatable conservatories, swimming pools, similar enclosed roomsat half§ 4 No. 3 WoFlV
Balconies, loggias, roof gardens, terracesas a rule at one quarter, at most at half§ 4 No. 4 WoFlV
Cellars, storage rooms outside the flat, laundry rooms, attics, drying rooms, boiler rooms, garagesnot at all§ 2 (3) No. 1 WoFlV
Commercial premisesnot at all§ 2 (3) No. 3 WoFlV

Parts of rooms below one metre in clear height are not listed in § 4 WoFlV at all — so they are not counted. This is where attic flats regularly fall apart: what a seller advertises as "95 m² under the slope" can be considerably less under the WoFlV. The second classic is the balcony. Counting it in full instead of at one quarter puts 9 m² too many into the lease for a balcony of 12 m².

Does the WoFlV apply to an ordinary lease? Not directly: under § 1 (1) WoFlV its provisions apply where living area is calculated under the German housing promotion act. The BGH, however, interprets the term "living area" in residential tenancy law "auch bei frei finanziertem Wohnraum grundsätzlich" — for privately financed housing too — by reference to the rules for subsidised housing, that is, the WoFlV (judgment of 17 April 2019 – VIII ZR 33/18). It is different only where the parties have agreed a different standard, or where another set of rules is locally customary in its entirety: the II. Berechnungsverordnung, DIN 283 or DIN 277.

One figure, three different legal consequences

The real error in the common account is not the 10% threshold itself but its reach. It answers one question only: from what point a smaller-than-stated flat is a defect. For everything else it does not apply.

IssueGoverning areaThreshold
Rent reduction (§ 536 BGB) stated area compared with actual area a defect only once the actual area is more than 10% below the agreed one
Rent increase (§ 558 BGB) the actual area alone no tolerance — the figure in the lease has no legal significance
Service charges (§ 556a BGB) actual area of the flat over the actual total area of the building no tolerance
Heating costs (§ 7 (1) HeizkostenV) living or usable area, but only for the base-cost share between 50% and 70% of the costs must be allocated by metered consumption anyway

Rent reduction: here — and only here — the 10% threshold applies

If the flat is more than 10% smaller than stated in the lease, that is a defect within the meaning of § 536 (1) sentence 1 BGB, and the rent is reduced by operation of law. The tenant need show nothing further — in particular not that the missing square metres actually bother them. Below the threshold, § 536 (1) sentence 3 BGB applies: "Eine unerhebliche Minderung der Tauglichkeit bleibt außer Betracht" — an insignificant impairment is disregarded.

One point matters for the amount: the reduction is calculated on the gross rent, not the net rent — our article on rent reduction from the landlord's side goes into that. And the discrepancy is a permanent defect: it does not go away, it cannot be repaired, and it bites in every single month of the tenancy.

Rent increase: the figure in the lease is simply irrelevant

Until 2015 a landlord could work with the agreed area as long as the discrepancy stayed within 10%. The BGH has abandoned that case law. Since then, any living-area figure in a residential lease that departs from the actual size is "ohne rechtliche Bedeutung" — without legal significance — for the application of § 558 BGB. What governs is the actual size alone.

This cuts both ways. If the lease overstates the area, the amount you may demand up to the local reference rent falls. If the flat turns out to be larger than assumed, you may not simply scale up to the new area: the cap under § 558 (3) BGB still applies. It limits the increase within three years to 20% — and to 15% in areas designated as tight markets by a state regulation. Our article on the rent increase cap shows how that is calculated.

Service charges: actual area over actual total area

Absent a different agreement, service charges are allocated under § 556a (1) BGB "nach dem Anteil der Wohnfläche" — by the share of living area. Which living area that means was settled by the BGH in 2018: the share of the flat's actual area in the total living area actually present in the economic unit. So both figures have to be right — a correct flat area is of little use if the building's total area comes from old paperwork.

Two special cases. Where a condominium flat is let, § 556a (3) BGB applies absent a different agreement: the allocation key is the one used between the owners — as a rule the co-ownership shares from the declaration of division, not the living area. And for heating, § 7 (1) HeizkostenV requires at least 50% and at most 70% of the costs to be allocated by metered consumption; only the remainder runs on area, so an area error hits in a muted form. Which costs may be passed on at all is covered in our article on non-recoverable service charges.

What an overstated figure costs in a held property

Take a flat recorded in the lease at 80 m² that measures 71 m² under the WoFlV — 9 m² less, a discrepancy of 11.25%. The net rent is €960 (€12 per m² on the contractual 80 m²), the service charge advance €200.

ConsequenceCalculationAmount
Monthly rent reduction 11.25% of €1,160 gross rent €130.50 per month
Tenant's reclaim 36 months × €130.50 €4,698
Forgone rent increase at €13 per m²: €1,040 assumed, €923 permissible €117 per month
Over-allocated service charges €12,000 total costs: 71/380 instead of 80/400 €158 per year

The third item is the most expensive because it is permanent: every future increase starts from a smaller area. The second is the most unpleasant because it arrives retrospectively — the standard limitation period under § 195 BGB is three years. And the fourth shows that the denominator was wrong as well: 400 m² total area on the old paperwork, 380 m² in fact.

There is one piece of good news. Where the rent is reduced because of the area discrepancy, the starting rent for the cap under § 558 (3) BGB is still the rent contractually agreed — not the reduced one (BGH, judgment of 17 April 2019 – VIII ZR 33/18). The reduction therefore does not eat into your headroom for increases on top of everything else.

Before buying and before the next lease

  1. A figure in a sales listing is not a verified figure. It often comes from a building drawing or from an older lease. Under § 3 (4) WoFlV, determining the area from a drawing is permissible only if the building was actually built that way — otherwise it has to be measured again.
  2. Check the price per square metre as well. In the example above, stating 80 m² makes the price per m² look 11.25% cheaper than it is on the actual area. In a comparison across properties that reshuffles the whole ranking.
  3. In a new lease, state the area conservatively. A rounded-down figure costs you little on the rent and removes the basis for a reduction. Where sloping ceilings or balconies make it uncertain, the area can also be left out and the rent agreed as a lump figure.
  4. Document a measurement and keep it. It is the basis for rent, for the service charge key and for sales documents at once — and in a dispute it is the only thing that counts.

What the courts have decided

Living area is a textbook case of the statute not answering the question: neither § 536 nor § 558 BGB mentions an area or a threshold. All three answers come from the VIII. Civil Senate of the BGH — and two of them expressly abandoned an earlier line.

BGH, judgment of 24 March 2004 – VIII ZR 295/03

This is where the famous threshold originates. If a flat has an area more than 10% below the one stated in the lease, that is "grundsätzlich einen Mangel der Mietsache im Sinne des § 536 Abs. 1 Satz 1 BGB" — in principle a defect entitling the tenant to reduce the rent. The Senate also made clear that no "zusätzlichen Darlegung des Mieters" is required showing that the shortfall actually impairs the contractual use. For landlords that means there is nothing left to argue about significance once the measurement is on the table.

BGH, judgment of 18 November 2015 – VIII ZR 266/14

For rent increases the Senate expressly abandoned the 10% tolerance. An agreement on the size of the flat is "auch bei Abweichungen von bis zu 10 % nicht geeignet" — not capable, even for discrepancies of up to 10%, of fixing a size that departs from the actual one; what governs is "allein die tatsächliche Größe der vermieteten Wohnung". The Senate added that the cap continues to apply where the flat later turns out to be larger. Basing a rent-increase demand on the contractual area therefore risks its invalidity.

BGH, judgment of 30 May 2018 – VIII ZR 220/17

The same turn for service charges, expressly abandoning a judgment from 2007. Where service charges are allocated by living-area shares under statutory rules, what governs is "im Allgemeinen der jeweilige Anteil der tatsächlichen Wohnfläche der betroffenen Wohnung an der in der Wirtschaftseinheit tatsächlich vorhandenen Gesamtwohnfläche" — generally the share of the flat's actual area in the total area actually present in the economic unit. In practice: the allocation key needs checking once in full, not just for the flat in dispute.

Frequently asked questions

Do I have to state the living area in the lease at all?

No. The statute requires no area figure; what is agreed is a rent for a particular flat. Without a figure there is no discrepancy and therefore no defect under § 536 BGB. You still need the actual area for rent increases and for the service charge key.

Does adding "approx." or "not an agreed characteristic" help?

The wording is not decisive. For rent increases, under VIII ZR 266/14 any figure departing from the actual size has no legal significance — a qualifier changes nothing. For a rent reduction it depends on the individual case whether a characteristic was agreed at all.

Is a balcony counted at one quarter or at half?

§ 4 No. 4 WoFlV says "in der Regel zu einem Viertel, höchstens jedoch zur Hälfte" — as a rule one quarter, at most half. The higher figure needs a reason on the facts, such as a particularly high-quality, sheltered position. One quarter is the default.

How far back can a tenant reclaim overpaid rent?

The standard limitation period under § 195 BGB is three years. When it starts to run depends on knowledge of the claim — in practice, the point at which the discrepancy was established.

What applies if I bought the flat with the lease running?

The lease transfers with the property — including the area stated in it and including the discrepancy. A measurement before purchase is therefore not a detail but a line in the calculation.

Areas, rent and service charges per property in one place

RenoDiary brings living and usable area, net rent and recoverable and non-recoverable costs together per unit — and shows what a corrected area means for cash flow and for the Anlage V tax schedule.

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Sources

This article provides general orientation and does not replace individual tax or legal advice within the meaning of § 3 StBerG. Whether an area figure was agreed as a characteristic, and how large a reduction turns out to be, depends on the individual case — the example figures are illustrations.