Gas extraction has caused increased seismic activity in the area of Groningen, bringing about considerable damage to houses. The houses are generally old masonry houses with flexible timber diaphragms. It is of importance to assess the response of these houses in order to apply proper retrofit measures. There has been substantial research on masonry, however there has been little exploration on timber diaphragms. For this reason, the TU Delft conducted cyclic tests on as-built and retrofitted timber diaphragms, as well as on the connections within the diaphragms. Timber diaphragms exhibit a nonlinear hysteresis under cyclic loading, which is caused by the nonlinear behaviour of the connections. This thesis focuses on the numerical modelling of the as-built and retrofitted diaphragm as tested at the TU Delft. Using ANSYS 18.2, the numerical models of the diaphragms are subjected to cyclic pushover analyses. As the connections within the diaphragms are the only source of nonlinearity, these are simulated first. For the nonlinear connections, it is essential that the numerical models can capture the pinching behaviour and strength degradation for cycles of the same amplitude. The numerical models of the connections are calibrated on experimental tests. With the models of the connections, the models for the as-built and the retrofitted diaphragm can be constructed. The results of the numerical models of the diaphragms are validated with experimental data. The models showed sufficient similarities with experimental results and are deemed suitable simulations of timber diaphragms.