In Ethiopia, expansive soils are found in wide areas. Those soils cause significant damage tornstructuresrnbuilt on them.rnParticularlyrnlightlyrnloadedrnbuilding withrndifferentrnfoundationrnrntypes such as isolated and mat foundations. Are more prone to damage there is arngeneral increase in building construction with increasing population at a very faster raternand large coverage of expansive soil. Therefore there is need to understand the characteristicsrnofrnthesernsoilrntypernandrnappropriaternfoundationrntypes.rnThe focus of this thesis is to evaluate the factors for moisture distribution with depth ofrnsoil, edge moisture distance and amount of soil heave by using proposed formula byrnRemon I. Abdelmalak (2007), the formula depends on pioneer work of Mitchell (1979).rnFor the determination of deflection, moment and shear of waffle mat foundation assumedrnas interconnected T-beam. For soil heave the beam to assumed as simply supported andrndesign as beam on elastic foundation using formula by M. Hetenyi (1946) to determinernsubgrade reaction of the soil. When soil shrinks the beam has no contact with soil andrnassumed as cantilever beam by using beam formula. rnDiffusivity coefficient has great sensitivity to moisture distribution with depth, edgernmoisture distance and soil heave. It has more than 100% increasing effect for moisturerndistribution with depth, edge moisture distance and soil heave when the soil goes fromrnuncracked condition to crack. Change of surface edge suction has secondary sensitivity.rnDrying period has little effect on the swelling characteristics of expansive soil. Differentialrnsoilrnheavernandrnedgernmoisturerndistancernincreasernwhen thernslabrndimensionrnincrease.rnBeam depth has great sensitivity to deflection of the T-beam for dry soils. The deflectionrnof the beam reduce by 75.6% when the beam depth increases two fold. Flange thicknessrnhas secondary sensitivity to deflection and flange width has small effect. For soil heavernbeam width has great sensitivity to deflection. Increases contact area and swelling pressurernwhenrnthernbeamrnwidthrnincreases.rnButrnotherrnparametersrnhavernalmostrnconstantrnsensitivityrnforrndeflection.rnWaffle mat foundation has reduced construction cost and time comparing with isolatedrnfooting. It has also high stiffness. Waffle mat foundation is a better foundation alternativernforrnlightrnloadedrnstructure onrnexpansivernsoil.