Several factors can affect the behaviour of the hollowcore floor slabs in fire. This paper analytically investigates the relationship between the fire resistance of the overall floor system and the floor length to width ratio as well as the type of side supports. The study uses beam grillage and shell elements to model the hollowcore slabs and the topping concrete under the platform of the non-linear finite element program, SAFIR. Different methods to model precast, prestressed concrete hollowcore floor slabs subjected to fire are also investigated. The results show that side supports can enhance the fire performance of hollowcore floor slabs provided that the spacing of the side supports does not greatly exceed the span length.