In tropical regions around the world a large amount of soils are in an unsaturated state. One of the most important problems affecting shallow foundations of light structures is the volumetric changes taking place when unsaturated soils are affected by changes in water content. Numerous studies about water migration and scaling laws in unsaturated soils have been done during the European NECER project. Most of these studies were carried out on sandy soils having minor volumetric changes. In this paper we give details about a study