How to Repair Erosion from Under Your Foundation

Stop Erosion Under Your Foundation

Erosion under a foundation usually comes from poor drainage or surface runoff washing away soil. You can repair it by redirecting water, stabilizing the ground, and filling voids beneath the slab or footing.

Inspect the Damage

Look for cracks in the slab, gaps between the foundation wall and soil, soft spots in the yard, or doors that stick. A level check across floors shows whether settlement has already begun. If the erosion is under a crawl space, inspect for washed-out soil and standing water.

Fix the Water Source

Before filling voids, control the water causing the erosion. Clean gutters and downspouts, extend discharge at least 6 feet from the house, and regrade soil so it slopes away from the foundation. Consider a French drain or surface swale if runoff concentrates near the wall.

Mudjacking and Slabjacking

A contractor pumps a cement grout or polyurethane foam mix under the sunken slab to lift and fill the eroded space. This works where the soil is mostly washed out but the foundation remains intact.

Helical Piers or Push Piers

When the foundation has settled or the soil is too weak to support a lift, piers are driven to stable bearing depth. This stabilizes the structure and can partially restore elevation.

Soil Replacement and Compaction

For minor washout, excavate the loose soil, replace it with compacted fill, and re-grade. Trenching along the footing and adding clean gravel improves drainage under the slab.

Prevent Future Erosion

• Keep downspout extensions in place year-round.
• Avoid planting large trees close to the foundation.
• Check grading after heavy rains and rework soft spots.
• Install a perimeter drain if your yard stays soggy.

Small washouts can often be patched DIY, but deep voids or ongoing movement need a structural contractor. A foundation specialist can tell whether mudjacking, piers, or drainage control is the right fix for your erosion pattern.