Schimmel (Mould) in a Rented Flat: Your Rights (2026)
Schimmel (Mould) in a Rented Flat: Your Rights
A defect, notify, set a deadline, then reduce (§§ 536, 536c BGB).
On the cause the burden of proof is split: the landlord must first show it does not originate in their sphere; only then must you show you heated and ventilated properly.
§ 536c BGBIn 60 seconds
Once the growth is more than trivial the rent is reduced by operation of law for the duration (§ 536 BGB), unless you caused the mould yourself.
Under § 536c BGB you must notify without delay and give an opportunity to remedy. Report late and you can lose the right to reduce and become liable for consequential damage (§ 536c Abs. 2 BGB).
You have to prove that mould is present, and where: with photos and, if needed, an expert report.
The landlord must first prove the cause does not originate in their sphere, for instance that there are no thermal bridges or building defects (BGH, VIII ZR 271/17). Only then must you show you heated and ventilated properly.
While the cause is unresolved your right to reduce stands. It is lost only once it is established that you caused the mould.
What the law says
If a defect appears during the tenancy, the tenant must notify the landlord without delay. If they fail to do so, they cannot assert the rights under §§ 536, 536a BGB to the extent that the landlord was unable to remedy because of the omission, and they are liable for the resulting loss. Working translation; the German original is the binding text.
What reduction is usual for mould?
There is no table in the law. The rate follows the severity, extent and location of the growth and is assessed case by case (§ 536 BGB).
| Severity | Rate typical in the case law* |
|---|---|
| Small patches, one ancillary room (e.g. spotting in the bathroom) | approx. 5% |
| Mould in one living room, contained | approx. 10–15% |
| Mould in several rooms (e.g. bathroom and bedroom) | approx. 20–30% |
| Heavy growth in several rooms, musty smell | approx. 50–80% |
| Flat uninhabitable / a health hazard | up to 100% |
*Indications from the case law, not a guarantee. When in doubt have it checked by a lawyer or a tenants' association.
The general rules on reduction, reservation, rate, forfeiture, are in Reducing the rent for defects.
What it means for each side
- Notify in writing immediately, with photos, the rooms affected and a reasonable deadline.
- Pay the full rent under reservation while the amount and cause are open.
- Note smell, extent and since when, that is what supports the percentage.
- Settle up once it is remedied; the reduction only covers the period of the growth.
- Respond to the notice and remedy the defect (§ 535 Abs. 1 BGB).
- Check the building side first. You have to exonerate yourself first.
- Document the cause and the remedy, with dates.
- Dispute an excessive rate in writing rather than deferring the repair.
Common mistakes
Without timely notice the reduction is vulnerable and you risk liability (§ 536c BGB).
Arrears and the risk of termination under § 543 BGB.
Cut more than is justified and you owe the difference and fall into arrears.
Without photos, dates and a copy of the notice nothing can be shown. And where improper heating and ventilation is established, there is no reduction at all.
What to do next
Document: dated photos of every affected area, notes on smell, extent and since when. Do it with BildProof, about two minutes a room →
Send written notice with a description, photos and a reasonable deadline (§§ 536c, 535 BGB).
Take the rate from comparable judgments and keep paying the full rent under reservation.
Settle up once it is remedied.
Frequently asked questions
Am I allowed to reduce the rent because of Schimmel?
Yes. Schimmel (mould) impairs the flat's fitness for use and is therefore a Mangel (defect); the rent is reduced by force of law for the duration of the defect (§ 536 BGB). The conditions are that you reported the Schimmel to the landlord (Mängelanzeige, § 536c BGB) and did not cause it yourself. Until the amount is settled, keep paying the full rent under Vorbehalt (reservation).
How much Mietminderung do I get for Schimmel?
There is no table in the law. The Minderungsquote (reduction rate) depends on the severity, extent and location of the mould and is decided case by case by the court (§ 536 BGB). Published rulings range from about 5 % for small mould spots in the bathroom, through roughly 10–30 % for mould in several rooms, up to 75–100 % for massive, health-endangering infestation. These are reference points, not guaranteed values.
Who has to prove who is at fault for the Schimmel?
The Beweislast (burden of proof) is split (BGH case law). As the tenant you only have to prove that the Schimmel exists. If there are indications of a structural cause, the landlord must first prove the cause does not lie in his sphere (e.g. no thermal bridges, sound building fabric, BGH VIII ZR 271/17). Only if he succeeds must you then prove you heated and ventilated correctly.
What should I do first when I find Schimmel?
Document and report first; do not reduce yet. Take dated photos of every affected spot and send the landlord a written Mängelanzeige (§ 536c BGB) at once, with a reasonable deadline to fix it. Only after that, and only under Vorbehalt, comes the Mietminderung. Without a timely notice you can lose your reduction right and may even owe Schadensersatz (damages).
Can I reduce the rent even if I might have ventilated incorrectly?
As long as it is not established that you caused the Schimmel, your reduction right stands (§ 536 BGB). The cause has to be clarified first, and the landlord initially carries the Beweislast for his own sphere (BGH). Still, reduce cautiously and only under Vorbehalt, so that if the cause question goes against you, you do not fall into payment arrears (§ 543 BGB).
This page gives general information as at the date shown. It does not replace legal advice on an individual case.