Current regulations on the use of structural timber in large multi-storey buildings can be restrictive due to a perceived higher level of risk with regards to fire safety. This research investigates the fire performance of unprotected timber floors for use in these types of buildings, involving both modelling and experimental testing. To fully characterise the behaviour of composite timber floor systems in fires, 3D numerical modelling was performed using finite element software. In order to validate the numerical results, full scale furnace testing of the floors was undertaken at the Building Research Association of New Zealand. The final goal of this research is to develop simplified design models to reliably predict the expected fire resistance of these floors for different floor geometries, spans, materials and loading conditions.