Investigating Weather during Construction
A little know service that might help determine the soil moisture before and during the construction of the house you are investigating is the Bureau of Meteorology.
The Bureau holds daily weather records for the last 100 years in some localities.
Use this information to determine the likelihood that the ground was moist at the time of construction. If you have observed slab doming and the perimeter soil moisture conditions are dry, consider coring the slab and checking soil moisture conditions under the slab. If they are moist – then the source of the soil moisture might be stormwater from when the slab was poured.
If the weather was very dry for the month preceding construction of the house, then look edge heave and external sources of soil moisture.
Correlate the BOM weather reports with soil moisture readings form the original soil test. Did the report indicate moist soil for the depth of the investigation?