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Tenancy law and rent reduction in the event of mold growth

Mold in rented homes is a widespread problem and can be costly. It is estimated that almost every 10th household in Germany is acutely affected by mold. For house and apartment owners, the question of how mold can be permanently removed arises when it comes to mold. If it is not a secondary infestation and the cause can be traced back to structural defects, this can mean expensive renovation measures.

If the property is rented out, the question of whether the tenant or the landlord has to pay for the costs of cleaning up the mold in the rented apartment can be complicated. The party responsible for the mold infestation is responsible for assuming the costs. However, it is precisely this fact that often has to be clarified in court. This guide is intended to present and explain the important basics of tenancy law on mold infestation and give advice on how to proceed in the event of an existing mold infestation.

Was tun bei Schimmelbefall

The information given here is only intended to provide an initial overview and does not replace specific legal advice in individual cases!

If there are any doubts about the existing legal situation and the existing rights and obligations, tenants and landlords should seek advice at an early stage. An overview of possible advice centers can be found here.

Rights and obligations of the tenant at a glance

Mietvertragsanalyse bei Schimmelpilzbefall
Beratungsgespräch aufgrund Mietminderung

Tenancy law in the event of mold in the apartment

When is the landlord liable for mold growth?

If the mold is clearly due to structural defects, the renter is fully liable for the damage. These can be cracks in the masonry, water damage from defective pipes, leaky roofs or wall cladding. Even after an improperly carried out (energetic) renovation, the landlord is responsible. If the landlord has the apartment renovated in terms of energy, for example by installing new windows or thermal insulation, he is obliged to inform the tenant whether this renovation means heating and ventilation behavior that is adapted to the tenant.

If the landlord does not comply with this duty of disclosure, the tenant cannot be held responsible for the damage. Furthermore, the tenant cannot be held responsible for mold caused by new building moisture, as the tenant cannot be required to compensate for the new building moisture through extensive heating and ventilation. The tenant can only be held responsible for non-compliance if specific heating and ventilation behavior is anchored in the rental agreement. Since 2009, a ventilation standard (DIN 1946-6) has stipulated that in new buildings and renovations (with more than a third of the windows being replaced), adequate air circulation must take place in the rooms without the assistance of the tenant.

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Was tun bei Schimmelbefall?

When is the tenant liable for mold growth?

If the mold growth cannot be traced back to structural defects, but rather to incorrect living behavior on the part of the tenant, the tenant is liable for the damage caused by mold growth. Insufficient heating and ventilation will increase the humidity in the apartment and mold will develop. Indoor plants, aquariums, terrariums that are too wet or drying clothes in the apartment favor mold growth, which is why living habits must be adapted to the circumstances of the apartment. Removing splash water from tiles after showering is also a tenant’s responsibility.


However, what exactly “appropriate living behavior” means in order to avoid mold has not been clearly clarified by the courts either. There are no specific rules as to how often and how long you have to air the room during the day. While some dishes consider ventilating twice a day for a total of 20-30 minutes as sufficient, other dishes consider ventilating two to four times for around 10 minutes each time as reasonable. However, the courts agree that tilting the window does not mean adequate ventilation, as this does not result in a sufficient exchange of air. The courts also disagree about the appropriate room temperature.

However, there is consensus that the room temperature must not fall below 16 ° C. If the heating and ventilation to prevent mold exceeds a normal level due to special requirements of the apartment, this must be regulated in writing in the rental agreement. The tenant is not obliged to adapt his living behavior to the living conditions to an extent that is no longer justifiable. Only if he specifies such living behavior in an individual agreement can he be held liable in the event of mold growth. The tenant cannot be held responsible for incorrectly set up furniture (too close to the outside walls), as the living conditions must be designed in such a way that the furniture can be set up on the outside walls without any problems.

How should tenants proceed in the event of mold growth?

Was tun bei Schimmelbefall?

If the tenant notices mold growth or moisture damage in the apartment, this must be documented and the landlord must be informed immediately, because the tenant is obliged to report any rental defects. Only if a notification of defects (§536c BGB), which names the defects and requests the landlord to rectify them, is submitted to the landlord, the tenant can enforce his rights. These can include the elimination of defects, claims for damages, termination without notice and a reduction in rent. If the notification of defects is submitted too late and the mold has spread further in the meantime, it can happen that the tenant is complicit in the mold infestation in question and he has to bear part of the costs of the damage.

If the landlord is aware of the mold, he is fundamentally obliged to repair the damage. Often tenants and landlords do not agree on who is responsible for the mold and who pays for the renovation. If the landlord refuses to take over the damage because he sees the tenant’s culpable behavior, it is not necessarily necessary to go to court. First, an attempt should be made to reach an out-of-court settlement between the tenant and the landlord.

mietminderung schimmel - schimmel mietminderung - schimmel mietrecht

Möchte der Mieter sichergehen, dass der Schimmelbefall nicht auf eigenes Fehlverhalten zurückführbar ist, ist die Beauftragung eines Gutachters ein probates Mittel. Im Idealfall können sich beide Parteien darauf einigen, einen Gutachter zu beauftragen, der die Ursache und damit Verantwortung für den Schimmelbefall ermittelt. Im Vorfeld sollte unbedingt abgeklärt werden, wer den Gutachter bezahlt. Zu beachten ist, dass das Ergebnis des Gutachtens keine rechtliche Bindung hat und auch vor Gericht nicht zwangsläufig angeführt werden kann, denn Gerichte bestellen eigene Sachverständige. Aus diesem Grund sollten sich Mieter zweimal überlegen, auf eigene Faust einen Gutachter zu bestellen, denn das Geld gibt es meistens auch nach dem Gewinnen eines Gerichtsverfahrens nicht zurück.

Rent reduction in case of disputes regarding the mold in the apartment

If no agreement can be reached with the landlord, it is possible to reduce the rent independently in order to get the landlord to act. However, there are some risks involved in doing this. If the rent reduction is not justified, i.e. the tenant is responsible for the mold, the landlord has the right to terminate the tenant without notice if the arrears exceed two months’ rent. This case law goes back to a court decision from 2012. In addition, the rent arrears must be paid. If the tenant is certain that the landlord is to blame for the mold infestation based on a self-commissioned report, the means of rent reduction in the case of mold is an effective instrument, but even then there is a residual risk. It is better to point out in the notification of defects that a certain part of the rent will be paid under reserve until the mold has been removed. If the tenant gets right in later legal proceedings, he can get this amount and get the money back.

Schadenersatz und Mietminderung bei Schimmel
Fachanwalt zur Mietminderung befragen

If the landlord cannot be induced to act by this measure either, the case can only be clarified in court. A specialist lawyer should then be consulted in advance as to which is the best course of action. It is important that all necessary documents (correspondence with the landlord, photos, etc.) are available and available to the lawyer. Responsibility for the mold infestation will be clarified in court at the latest.

Mietrecht: Miete mindern bei Schimmel in der Wohnung

Court decisions in the event of mold infestation - reduce rent in the event of mold

If a tenant asserts his or her right in court, the court must clarify who is responsible for the mold infestation. For this purpose, the court appoints an expert who examines the circumstances on site and comes to a final assessment. Even if there are objective criteria for assessing the subject of mold, every court decision is subject to an individual assessment.

In court, it is the landlord’s duty to prove that the mold infestation is not his area of ​​responsibility, i.e. that the damage cannot be attributed to structural defects or damage. Only when the landlord can prove beyond any doubt that he is not responsible for the mold does the tenant have the burden of proof.

The tenant must then prove that he has not contributed to the formation of mold through incorrect living behavior (incorrect heating and ventilation behavior). The judge listens to the arguments, weighs them against each other and, in connection with the expert opinion, comes to a judgment as to who has to bear the costs.

Often the question of guilt with regard to the mold growth in the rented apartment is not entirely clear. In many cases, both tenants and landlords are responsible for the mold growth. In these cases, the mold can be traced back to structural defects, but the tenant has contributed to its spread through incorrect heating and ventilation. The costs for the damage then often have to be borne in equal parts.

Conclusion – tenancy law and rent reduction in the case of mold

In principle, the party must pay for the costs of the mold remediation that is responsible for the mold infestation. This often leads to disputes between tenants and landlords. In the event of an escalation, a court decides on the question of guilt.

Mold in your rented apartment?

inVENTer supports you in the fight against mold!

  • You have these rights as a tenant
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