Australian Standard AS 2870 – time for a change: With specific reference to the slab heave problem with waffle rafts

The purpose of this paper is to review the efficacy of Australian Standard AS 2870 [1] to regulate site classification, design, construction and maintenance of residential slabs and footings. This review identifies a number of issues with AS 2870 relating to the slab heave problem with waffle rafts. It demonstrates how AS 2870 may be applied to hold home owners responsible for damage to their new homes, caused by foundation movement as a result of abnormal soil moisture conditions developing after the owners have taken possession of their new homes. It also demonstrates that slab heave, popularly believed to be caused by deficiencies in the stormwater drainage systems of the dwellings, is not the principal cause of damage. A limit state methodology for ultimate strength design of residential slabs is recommended as a cost-effective way to mitigate the slab heave problem with waffle rafts. Graphs are included to address the issues with AS 2870.