The distribution of loads in the props and slabs, when the weight of newly cast slabs is supported on previously cast slabs with props between, was studied. Preloaded steel and aluminium props were considered. It is shown that the mechanical properties of the slabs and props are such that the upper slabs carry 75% of the load and the lower slabs only 25%. Higher prop preloading would be required to achieve more uniform load sharing between the upper and lower slabs, but is unlikely to be achieved in practice. It is also suggested that aluminium props should be retightened immediately before a new slab is poured, as they will exhibit a significant length reduction with a drop in temperature. Simplifying the process by eliminating back-props and supporting the weight of a new floor on the recently-constructed floor immediately below, is also discussed. 9 refs.