Tree Roots and Your Foundation: What Root Barriers Do

They can add to foundation movement, mostly by changing the moisture in the soil. This matters most in the Piedmont, where clay already swells when wet and shrinks when dry.

A mature tree close to the house draws water out of the surrounding soil, and during a dry Carolina summer that can shrink the clay near the foundation more than the weather alone would. That adds to the seasonal movement that stresses footings and piers, and it can show up as a floor dipping over one side of a raised home.

The signs of soil movement are the same whatever the cause: floors that slope or dip, doors that stick, and cracks in drywall or masonry. What points toward roots is where the movement is. A dip on the side of the house nearest a large tree, especially one that gets worse in dry summers, is worth noting.

Roots are rarely the only factor. Crawl space moisture, soil that washed out from under a footing, and supports that were undersized from the start can produce the same signs, which is why the inspection looks at all of them.

A root barrier is a sheet of durable material set upright in the soil between a tree and a house. It steers roots downward and away, so they do not spread into the soil right next to the foundation. The idea is to keep the soil near the footings from drying out as much in a dry season.

A barrier only affects future root growth. It does not lift or level a home that has already moved, and it does not repair a support that has settled.

When a support under a raised floor has settled, it is given firm bearing again, often with adjustable steel jacks on footings, and the floor is brought back toward level in stages. Pier and beam repair explains that work, and damaged framing is handled through repairs to crawl space framing.

Movement that affects a whole foundation is covered under foundation repair. When a tree is a concern in its own right, an arborist is the right resource for the tree.

Roots dry the soil out; crawl space moisture does the opposite. Water that stands under a home can soften the ground beneath pier footings and keep the framing damp. Both swings in soil moisture can move supports.

Keeping the crawl space dry with crawl space drainage to a sump where water gets in and a liner over the soil helps keep conditions under the home steadier.