the invention provides a method for making a concrete floor slab using sub - grade waterproofing in a manner that favors the use of water - based adhesives for affixing floor covering materials . the method comprises casting a hydratable cementitious composition onto a flooring membrane , the composition having a shrinkage reduction admixture and a water : cementitious binder ratio sufficiently low that substantially all of the water moisture is retained in the hydration reaction , and achieving a fully adhered bond with the flooring membrane .