Slabs-on-grade foundations on shrink-swell soils are one of the most efficient and inexpensive solutions for these kinds of problematic soils. It is commonly used in residential foundations or any light weight structure on shrink-swell soils. This book presents a new simple method to design stiffened slab on grade on shrink-swell soils. A number of topics are covered that needed to be addressed in the development of the method. They include: a new laboratory test to determine the soil diffusivity based on measuring soil sample volume changes, instead of suction measurements, with time; a design chart relating the soil diffusivity at field to soil diffusivity determined at lab addressing network of soil cracks; the derivation of a new closed form solution for the soil mound shape by using Mitchell s equations for moisture diffusion under a partially covered soil; the results of suction change at the soil surface based on finite element simulations of a weightless cover on shrink-swell soils; new design procedure for slab-on-grade foundations on shrink-swell soils based on soil-structure-weather interaction finite element analyses.