Much of Florida's natural soil and sand recovered from the phosphate mining/beneficiation process there contain significant quantities of radium. Buildings constructed on these high-radium soils have been found to contain elevated radon levels. To decrease elevated indoor radon levels, Florida's legislature instructed its Department of Community Affairs to develop new construction standards for radon-resistant buildings, primarily slab-on-grade constructions. Primary research objectives were as follows: to establish the capability to measure concrete's permeability and diffusivity; to measure these parameters in a small sampling of the typical types of Florida concrete; and, if possible, to correlate the physical parameters of the concrete (mix design, porosity, surface finish, etc.) to the measured diffusion and permeability coefficients.