Due to the increasingly stringent energy efficiency requirements, timber frame constructions (often as low-energy or passive houses) can be found all over Europe. Though, the circumstances (indoor/outdoor boundary conditions, composition of the wall,…) in which the constructions are used often differ. This can lead to a different hygrothermal behaviour and increase the risk on early failing by mould growth and wood rot, especially with the growing tendency to use untreated wood. At present, several simplifications and shortcomings exist in the different research fields to predict and avoid moisture related biological damage in timber frame constructions in a reliable way. By joining the know-how and expertise of Woodlab-UGent and the Building Physics Section of KU Leuven, the current project aims at the development of a reliable risk assessment methodology for mould growth and wood rot on timber frame constructions. This requires an overall methodology based on fundamental research and input on different aspects. First of all, as several of the determining parameters are stochastic in nature, a probabilistic framework is proposed. Focus will be on efficient sampling methods, sensitivity analysis and metamodelling to identify the critical influencing parameters and sequences of boundary conditions. In combination with advances in hygrothermal simulation of timber frame constructions and elaborated resistance prediction models based on dynamic measurements, an overall stochastic risk assessment method is envisaged.