Trees drink from the same soil your house stands on.

A mature tree is a pump. It pulls water from the soil every day, hardest from the ground nearest its trunk, and in clay that pumping changes the ground's volume. USDA survey data shows clay dominating Los Angeles and San Diego area soils, and clay shrinks as it dries. When the drying is concentrated under one side of a home, that side's soil contracts while the far side stays moist and swollen, and the foundation ends up bridging two different soils. The supports over the dry side settle, and the house tilts toward the tree.

The upstairs evidence is indistinguishable from any other differential settlement: sloping floors, sticking doors, cracks over openings. Which is exactly why the diagnosis has to separate root drying from the drainage problems that mimic it, a distinction the evaluation makes with elevation measurements and soil evidence rather than guesswork. The symptom picture is laid out on our floor settlement symptom page.

A root barrier is a permanent underground wall of high density panels set vertically in a trench between the tree and the foundation, deep enough to intercept the active root zone. Roots that reach it are deflected downward and away, toward soil where the tree can drink without unbalancing the house. The tree keeps its water supply, the foundation side of the line keeps a consistent moisture level, and the crawl space stops hosting root systems that displace soil and press on piers.

Depth is the honest variable. A barrier that stops above the active root zone simply gets grown under, so the panel depth is set by the roots actually found during the evaluation, not by a standard number. Installation is a trench along the planned line, panels set and joined, soil restored, typically finished in a day or two.

Root drying and poor drainage produce the same differential settlement from opposite directions: one removes water unevenly, the other adds it unevenly. Installing a barrier against a drainage problem fixes nothing, which is why the evaluation checks both stories before either fix is proposed. Elevation mapping shows which side settled; soil and root evidence show whether the dry side matches the tree; the drainage picture shows whether water, not roots, explains the pattern, in which case the answer is stormwater drains rather than panels.

And when settlement has already happened, the barrier only stops the cause. Supports that dropped need direct repair, usually steel floor jacks and new footings under the affected section. The evaluation separates the two scopes with measurements so you can see what the tree caused and what it costs to correct.