Technical issues

The performance of slabs on moisture reactive soil involves many variables, yet the original authors of AS 2870 preposterously prescribed slab design solutions requiring only two input parameters – Site classification and type of construction. Therefore, many practising engineers do not design slabs and footings in the true sense of the term, they simply select a design solution prescribed in AS 2870, comfortable in the knowledge that their selections are deemed-to-comply. This widespread practice raises the issue of the engineering community’s professional duty of care to home-owners, as well as technical issues, including but not limited to the following:

  • Applicable ranges of design Ys values in AS 2870 Table 2.3 are too broad.
  • Deemed-to-comply slab design solutions are independent of soil stiffness.
  • Deemed-to-comply slab design solutions are independent of floor plan dimensions.
  • Designs are based on a one-way action beam model for what is a two-way action plate problem.