Mould, always mould
 

Although repeated measures were taken to rectify the situation, the condition of the flat deteriorated increasingly – a lawsuit was finally unavoidable.

The tenant had been living in a flat in the Volkhoven/Weiler district of Cologne since 2016. Mould repeatedly appeared there, which the landlady also tackled several times. Among other things, windows were readjusted, thermal bridges were removed with insulation, the balcony door connection was sealed with fleece, mould was removed and a reveal and window lintel were fitted with interior wall insulation. But none of this helped: the mould appeared again – and this time in almost the entire flat, as evidenced by photos taken by the tenant. The landlady, on the other hand, claimed that no further infestation had occurred since the last renovation measures. She questioned whether the photos were up to date and attributed the mould to incorrect heating and ventilation behaviour. The Cologne Tenants' Association represented the tenant out of court and demanded the final removal of the damage and its causes, setting a deadline. When no further measures were taken, the tenant brought an action before the Cologne district court. 

The court ruled in favour of the claim. It found that the flat was not in a proper condition and that the landlord was obliged to ensure this during the rental period. The tenant had substantiated the renewed mould infestation, including by submitting current photos and a proper notice of defects. The landlord's simple denial with ‘not knowing’ was inadmissible – she would have had to get a picture of the situation herself. In addition, it was the landlord's responsibility to prove that her measures were successful. She failed to provide this proof. The so-called ‘sphere theory’ evidence that the cause did not originate from her area of responsibility was also unsuccessful In the course of the proceedings, an expert opinion and a supplementary expert opinion were obtained. The latter came to the conclusion that the physical condition of the external walls – in particular the reveals and external corners - had actually deteriorated as a result of the measures carried out by the landlord. The previously proper wall structure had been altered by the internal insulation in such a way that the minimum thermal insulation was no longer met. The expert confirmed that mould infestation was possible under these conditions, even with completely normal living conditions.

Conclusion: This case shows how complex the causes of mould can be – and that even well-intentioned renovation measures can worsen the situation. Only a supplementary expert opinion turned the tide in favour of the tenant.