A substantial proportion of low-rise construction in Britain is on filled ground and probelms due to settlement of the fill have occurred. Most poorly compacted fills undergo a reduction in volume when inundated or submerged for the first time, which if it happens after building construction can cause serious damage. This phenomenon, usually termed collapse compression, is often the most serious hazard for buildings on fill. The increase in moisture content of the fill which triggers collapse compression can be caused either by downward infiltration of surface water or by a rising ground water level. Where non-engineered fill is treated to improve its load-carrying properties, a primary objective should be to eliminate any significant collapse potential. Similarly, the specification and control procedures for placement and compaction of an engineered fill should aim to eliminate this type of volume change within the fill.