Settlement and tilt of low-rise buildings

Where deep foundations are not an economically viable solution, foundation problems may occur at low-rise housing developments on poor ground. It is usually feasible to provide a raft foundation relatively cheaply for lightly loaded buildings. When differential settlement occurs, foundations of adequate stiffness will cause the building to tilt as a rigid body, and will prevent significant distortion of the building and consequent cracking of the walls. A number of case histories of tilted buildings are presented to illustrate the magnitude of tilt that has been observed with different ground conditions, and the remedial actions that have been undertaken. Noticeability is a key factor in assessing the acceptability of tilt for low-rise residential buildings and their occupants, and tilt typically is noticed when it is in the region of 1/250 to 1/200. Where tilts of the magnitude of 1/100 or greater are measured, or the measured rate of increase of tilt indicates that this degree of tilt will be exceeded, some remedial action should be taken, which is likely to include re-levelling the building.