Abstract: Expansive clay soils swell when wetered and shrink when dried out, and hence give rise to ground movements which can further cause structural damages of buildings. The effects of initial water content and load applying or releasing on the result of laboratory swell shrink indices test are studied. The influence of site conditions on potential volume of an expansive clay foundation, especially these factors causing significant change in water content of underlying soil mass, are discussed in this paper. Instead of natural water content, shrinkage limit and swelling limit should be used as initial water content in laboratory test. Before foundation design, site conditions, such as vegetation, precipitation, groundwater table, water drainage, etc. must be considered carefully. For important structures, different methods should be used and compared with each other to evaluate potential volume change of expansive soil more reasonably.