This California home is an example of what occurs when soil material becomes heavily water saturated under residential and commercial structures.
Usually the source of underground saturation is determined with drilling, mapping of the subsurface conditions, water sampling, soil samples including moisture contents which are mapped to show the locations and elevations.
It is vital that buyers be certain of property they are considering for purchase. Buyers should be aware, before purchase, of the geological formational foot print area under the structure. Question the site, drilling logs, and geotechnical report to provide your own personal knowledge before attempting to build or purchasing a home. When possible a third party consultant also acts as a site foundation analyst.
Once the subsurface investigations are complete the buyer will receive a report for the site geological conditions, depth and location which should show the weathered and un-weathered formational material shape and elevations. The formational subsurface terrain and the shape of the above land vary in the effects and structural integrity of the building site of the home.
The Cities Building Department of General Services and Permitting are the offices that determine the site locations to build and which areas to avoid. Information history is provided by these departments for these purposes.
For sale purposes, view and location is a valued commodity. In some cases building a home in prime location with a view might indicate the home is too close to the slope edge. Unfortunately, the forces of nature and geological change caused by erosion, seismic movement, hydrostatic pressure, time and wear can lead to structural failure.
In contrast, formational material may be found in a beneficial geological condition. If not, it can be removed during construction formed into a formational material keyway. This will interlock the home or building in addition to benching the slope. This is sometimes referred to as certified fill. In other words, what was an unknown subsurface condition became keyed into un-weathered solid bedrock. The grading pad is completed by stair step interlocking into weathered formational material as the pad is graded to reach the desired elevation.