Klartext Recht

Rent Reduction for Mold: How to Proceed with Legal Certainty

2026-06-04

Last Updated: June 2026
Reading Time: approx. 6 minutes

Legal Disclaimer: This article provides legal information based on the German Civil Code (BGB). It does not constitute legal advice. In the event of mold infestation and an impending legal dispute, you should consult a tenants' association or a specialized lawyer.

Rent Reduction for Mold: How to Proceed in a Structured Way

Mold infestation in an apartment is not only a visual problem but often poses a significant health risk. As a tenant, you do not have to accept this condition without complaint. German tenancy law provides for an automatic rent reduction in the event of a significant reduction in the suitability of the rented property. But beware: In order to minimize the risk of termination due to rent arrears, formal steps must be followed precisely. You can find more basic information in our comprehensive tenancy law guide.

1. The Legal Basis: The Rental Defect according to Section 536 BGB

The central pillar for your claims is Section 536 BGB. It regulates when the rent is reduced:

  • If the rented property has a defect at the time it is handed over to the tenant that negates its suitability for contractual use, the tenant is exempt from paying the rent for the time during which its suitability is negated.
  • For the time during which its suitability is reduced, the tenant only has to pay an appropriately reduced rent.
  • An insignificant reduction in suitability is disregarded.

2. Landlord's Maintenance Obligation (Section 535 BGB)

The landlord is legally obliged to keep the apartment in a condition suitable for contractual use.

  • According to Section 535 (1) sentence 2 BGB, the landlord must hand over the rented property to the tenant in a condition suitable for contractual use and maintain it in this condition during the rental period.
  • This also includes the removal of mold, provided that it is caused by structural defects (e.g. thermal bridges or defective pipes).

3. The Defect Notification: The First Mandatory Step

Before you reduce the rent, you must report the defect.

  • Immediate reporting: Inform the landlord immediately in writing about the mold infestation.
  • Setting a deadline: Set a reasonable deadline for repairing the damage.
  • Preservation of evidence: Document the mold with photos and keep a log of your ventilation and heating behavior.
  • Important: Without a defect notification, you may lose your right to reduction and make yourself liable for damages to the landlord if the mold worsens due to your silence.

4. How High Can the Rent Reduction Be?

There is no rigid legal table. The amount of the reduction is always an individual decision and depends on the impairment of the quality of living. The following guide values can often be found in case law:

  • Mold in the living room: 10% to 20%
  • Mold in the bedroom: 15% to 30%
  • Large-scale infestation in several rooms: up to 100% (if the apartment is uninhabitable)

Similarly high reductions can also occur with other serious defects, for example if the heating is broken in winter.

5. Content Control of the Rental Agreement (Section 307 BGB)

Landlords often try to exclude their liability for mold through clauses in the small print or to impose extreme ventilation obligations on the tenant. This is where the content control according to Section 307 BGB comes in:

  • Provisions in standard contract terms are invalid if they unreasonably disadvantage the tenant contrary to the requirements of good faith.
  • An unreasonable disadvantage can result from the fact that the provision is not clear and understandable (transparency requirement).
  • In cases of doubt, a disadvantage is to be assumed if the clause restricts essential rights or obligations in such a way that the purpose of the contract is endangered.

Smart Preparation through AI Analysis

Assessing whether a clause in your rental agreement is valid or how reduction steps should be structured can be complex. Jurivo supports you in your preparation:

  • Clause Orientation: The AI helps you check whether your rental agreement has typical blanket maintenance clauses that frequently raise questions with regard to Section 307 BGB.
  • Pattern Matching: We help you classify whether your defect notification corresponds to the usual formal structural structures that are common under Section 536 BGB.
  • Structured Drafting Aid: Get guidance and text support to systematically set up your communication with the landlord.

💡 Check rental agreement for maintenance obligations
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Status of Legislation: June 2026.