Slab Foundation Repair for Cracks, Settling, and Uneven Floors

A slab foundation, or slab on grade, is a concrete slab poured directly on the prepared soil that serves as both the foundation and the ground floor. It has no crawl space or basement beneath it.

Slab foundations are common in newer Carolinas subdivisions, from the suburbs around Charlotte and the Triangle to developments in the Sandhills. Because the home sits directly on the slab, it responds quickly to what the soil does. In Piedmont clay, seasonal swelling and shrinking can heave or settle sections of the slab, while in sandy Sandhills soils, erosion and poor compaction can leave parts of it unsupported.

The signs show up inside and out. You may see cracks in floor tile or grout first, then doors that stick or stop latching in the same part of the house. Many homeowners also notice drywall cracks at the corners of doors and windows, and floors that feel uneven underfoot.

In the Piedmont these signs often track with wet and dry seasons as the clay changes volume. A plumbing leak under a slab can also wash out the supporting soil over time, and when settlement is concentrated in one area you may notice one corner sitting lower than the rest of the home.

We start by working out whether the slab is heaving upward, settling downward, or cracking from shrinkage, because each points to a different fix.

For settlement, steel piers under the slab carry its weight down to firmer soil. Where a section dropped over a void, injecting polyurethane foam under the slab can lift and support it.

Stable cracks are sealed, often with epoxy injected into the crack, using the same approach as our foundation crack repair. When the footings along a whole side of the house are settling, the repair may be underpinning the perimeter footings with piers.

Sealing slab cracks on their own is only a surface fix when the slab is settling. In that case the slab is stabilized first, with piers or foam support, so the repair holds.

A slab foundation has no crawl space to inspect from below, so the inspection reads the symptoms: the crack pattern, how doors and windows fit their frames, and how level the floors are from room to room.

We explain what we find in plain language and lay out the options. Every slab repair begins with a free slab foundation inspection.