Summer temperatures regularly exceed 100 degrees to shrink upper clays, while alluvial gravel washes shift under heavy footing loads down to 25 feet.
Census records document that owner-occupied homes account for 46.8% of properties in San Bernardino, with many neighborhoods resting on loose alluvial outwash from the mountains. During wet winter storms, water runs off nearby peaks and saturates the porous subgrade, softening the bearing plane under exterior walls. When severe summer heat removes that moisture, unbonded gravels consolidate under building weight, causing outer foundation perimeters to settle unevenly.
The Portland Cement Association notes that concrete foundation beams require uniform subgrade bearing across their full span to avoid diagonal shear failure. When San Bernardino ground subsides beneath a single corner, the unsupported concrete must bridge the void using only internal tension. Surface mudjacking cannot resolve this condition because pumped slurry washes through coarse gravel. Hydraulic piers bypass weak surface soil completely, anchoring into dense load strata.