Mold in Your Apartment: Your Rights as a Tenant

When Is the Landlord Liable for Mold?

Mold in a rental apartment is a serious defect. Under § 536 BGB, tenants have the right to a defect-free apartment. If mold occurs due to structural defects – such as leaky windows, insufficient insulation, or faulty sealing – the landlord is obligated to fix it.

Mold from Structural Defects vs. Improper Ventilation

Landlords often argue that mold was caused by improper heating and ventilation habits. However, the burden of proof lies with the landlord: they must demonstrate that the tenant caused the mold. If they cannot, a structural defect is presumed.

• Structural causes: Thermal bridges, leaky joints, inadequate ventilation in bathrooms without windows
• Tenant behavior: Only in cases of demonstrably insufficient ventilation (e.g., permanently closed windows with high moisture production)

What Rent Reduction Is Possible for Mold?

The amount of rent reduction depends on the extent of the infestation. Courts have awarded between 5% and 100% rent reduction depending on severity:

• Minor mold in one room: approx. 5–10%
• Large-scale infestation in the bedroom: approx. 15–20%
• Health-threatening mold in multiple rooms: up to 50%
• Apartment uninhabitable: up to 100%

Calculate your individual rent reduction →

How to Proceed Correctly

1. Document the mold – Photos with dates, size of the affected area
2. Send a defect notice to the landlord – In writing by registered mail, with a deadline for remediation. Create defect notice →
3. Announce the rent reduction – After the deadline expires, you may reduce your rent

Important: Report the mold to your landlord immediately. Concealing a defect puts you at risk of liability for damages.