A new method is presented for measuring permeability evolution during the rapid hydration phase of cement set. The method exploits the hydration-induced pore pressure decline in the cement by using it as a driving force for fluid dow and thus minimises damage to the delicate evolving matrix structure. This represents an improvement on traditional measurement techniques, where a pressure gradient is imposed on the sample, which can cause much greater damage to the matrix. Cement is modelled as an elastic frame filled with a diffusing pore fluid, with fluid consumption represented by an effective universal sink, or suction, term. This sink term is proposed as a fundamental material property of a setting cement, which is independent of curing conditions. Results are compared with early-time measurements of permeability made using a more conventional test scheme where water is forced through a sample.