Precast, prestressed hollow core concrete slabs have been widely used in recent years. In a previous paper at ACMSM19 the authors presented a simple computational method that could be used in design for modelling the structural behaviour of hollowcore concrete slabs in fires. The model proposed at that time consisted of a grillage system using beam elements to include the thermal expansion in both directions and to simulate the vertical cracking in the flanges, with the topping concrete modelled using shell elements. The simulation showed good agreement with the experimental results. This present paper shows that it is possible to avoid using shell elements to model the topping concrete and instead model the topping concrete as part of the hollowcore slabs. This beam grillage method of modelling both hollowcore slabs and topping concrete gives similar results to using beam and shell elements, but requires less computational time.