Expansive soil is the reason most of this website exists.

Expansive Soil: diagnosed and explained.

Expansive soil is clay rich ground that swells when it absorbs water and shrinks as it dries, and that cycle drives most foundation damage in the Southwest. It is not a symptom you see; it is the cause behind the symptoms you do. The clay is made of microscopic plate shaped particles that absorb water between their layers, and when they do, the soil physically grows, swelling with enough force to lift slabs, push walls, and rack a wood framed house. When the moisture leaves, the soil shrinks back, and the foundation that rode up now rides down, rarely evenly. A home on expansive soil is effectively floating on a material that changes size with the weather, and the damage vocabulary is familiar: drywall and stucco cracks that open and close with the seasons while trending worse, doors that stick in some months and swing free in others, slab cracks, sloping floors, stair step cracking in masonry, and gaps at ceilings and baseboards. What makes expansive soil distinctive is the rhythm. Damage driven by it breathes with the moisture calendar, worsening after wet winters or during deep droughts, and it concentrates wherever moisture is uneven: the heavily irrigated side of a house versus the dry side, the corner near a downspout, the zone over a slow leak. Southern California, Arizona, and Nevada are heavily mapped with these clays, which is why foundation work here is less about fixing concrete and more about managing the relationship between a house, its water, and a soil that refuses to hold still.

For the repair side of this, the foundation repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than expansive soil.