Tenancy law06. März 2026|
What to do about rental defects? Mould, noise, heating – your rights as a tenant
Rental defects such as mould, noise or heating problems? Learn what rights tenants in Switzerland have and how to proceed correctly.
Mould on the walls, a broken heating system in the middle of winter, or constant construction noise – rental defects are unfortunately part of everyday life for many tenants. But what rights do you have when your apartment is not in proper condition? And what is the best course of action? This article provides you with a practical guide.
What qualifies as a rental defect?
A rental defect exists when the rental property does not correspond to the contractually agreed condition or is impaired in its fitness for the intended use. Swiss tenancy law distinguishes between different levels of severity:
- Serious defects: the apartment is uninhabitable or its use is severely restricted (e.g. heating failure in winter, large-scale mould infestation, no running water).
- Moderate defects: use is possible but noticeably impaired (e.g. leaking windows, defective appliances, minor moisture damage).
- Minor defects: small faults that hardly restrict use (e.g. a dripping tap, a sticking roller blind).
Mould in the apartment – who is liable?
Mould is one of the most common rental defects and at the same time one of the most disputed. As a general rule: the landlord is responsible for the defect-free condition of the apartment. If the mould has structural causes – for example, poor insulation, leaks or insufficient ventilation options – the landlord must rectify the defect.
However, the landlord may argue that the mould was caused by the tenant's incorrect heating or ventilation habits. Clarifying the causes is often difficult in practice. Our tip: document the mould immediately with photographs and report it to the landlord in writing. In the event of a dispute, an independent expert can provide clarity.
Noise – what must tenants tolerate?
Noise can have various causes: loud neighbours, construction noise or traffic noise. Not every type of noise constitutes a rental defect. What matters is whether the noise was foreseeable at the time the contract was signed and whether it exceeds the usual level.
Construction noise in the neighbourhood that was not foreseeable when the contract was signed can constitute a rental defect and entitle the tenant to a rent reduction. The same applies if the landlord themselves carries out renovation works in the building that significantly impair comfort. Noise from neighbours, on the other hand, is primarily a matter for the property management.
The correct procedure for rental defects
Following the correct procedure for rental defects is crucial to preserving your rights:
- 1. Document the defect: take photographs and videos. Note the date and time.
- 2. Inform the landlord in writing: send a defect notification by registered letter. Describe the defect precisely and set a reasonable deadline for rectification.
- 3. Wait for the deadline: give the landlord the opportunity to rectify the defect within the set deadline.
- 4. If no action is taken: send another reminder to the landlord. Set a final deadline.
- 5. Rent reduction / deposit of rent: in the event of continued inaction, you can demand a rent reduction or deposit the rent with the conciliation authority.
Rent reduction – how much is appropriate?
In the case of an acknowledged rental defect, the tenant is entitled to a reasonable rent reduction for the duration of the defect. The amount of the reduction depends on the severity of the defect. There are no fixed percentages, but the following indicative values from case law apply:
- Minor defects: 5–10% reduction
- Moderate defects: 10–30% reduction
- Serious defects: 30–100% reduction (up to 100% if the property is uninhabitable)
The rental deposit as a means of pressure
If the landlord does not rectify the defect despite a reminder, the tenant may deposit the rent with the competent conciliation authority (Art. 259g OR). Important: the deposit must be announced to the landlord in writing beforehand. Do not simply pay less rent – without a proper deposit, you risk termination for late payment.
The conciliation authority holds the money in custody and decides in the event of a dispute whether and to what extent a rent reduction is justified.
Tenancy law06. März 2026
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