The mechanical response and durability of building materials is highly influenced by the atmospheric conditions. Temperature and air humidity have a great influence on the transfer of water and contaminants in the porous structure of these materials. This paper focuses on the effects of moisture content and/or moisture dynamics which are even more important when rupture is due to crack. Climatic variations are simulated and a lifetime model is proposed. The “climat” method consists in processing a wide amount of meteorological records from four French sites covering different climates, in order to identify their statistical properties, identify their time auto-correlation characteristics, be able to rebuild synthetic signals with the same or different characteristics. The generic model is able to reproduce a very large amount of simulations, which is necessary for reliability or statistical analyses. The lifetime model predicts the incubation time and the time of crack propagation until the failure. As temperature has a smaller influence on the time to failure than relative humidity, its effects are not directly taken into account in the model. Predictions of the proposed model for various air humidity simulations are compared with creep test results obtained on notched LVL beams under various climatic conditions.Read less <