Methods of investigation and repair of light construction on reactive soil not complying with expectations

Following the procedures of Australian Standard AS2870 does not always give correct, concise, or usable answers to determine why buildings fail. In fact, the answers can be misleading. Throughout the evolution of Australian Standard 2870, stump and bearer construction has been eliminated from reactive sites as has hold down screw piles; neither are in the current edition of Australian Standard 2870. Further, there is a lack of literature on the research that went into Australian Standard 2870 (1986) and why there are now beams for H2D sites (i.e. highly reactive) having an I value (uncracked stiffness) 2.7 that of the 1986 edition. Methods of investigation used today include relative level survey via a water level only, photographic record of cracks and distortion, and geotechnical investigations (bore logs) to determine soil moisture, free swell, and consistency index (Atterbergs Limits). This paper recommends, in necessary cases, that plumbing investigations utilising a newly developed methodology be implemented. This methodology has verified that water is flowing from trenches external to the site in close to 100% of the cases where heave was observed. Three example cases are used as points of discussion, including recycled sites, which have problems of abnormal moisture before construction starts, new construction on new subdivisions, and a case where abnormal moisture conditions happened well after construction. Ultimately the method of repair permanently is hold down screw piles retrofitted, or attempt to control moisture variations after the failure methodology has been corrected.