Why is my driveway or patio lifting, sinking or cracking?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: Driveways, sidewalks and patios are thin slabs resting directly on the soil, so they show soil movement quickly. On Oklahoma clay they can lift when the soil swells, sink when soil washes out, compresses or dries, and crack in either case. Their movement is a clue about water and soil around the house, but it does not by itself mean the house foundation has moved.

Why does flatwork move so easily?

"Flatwork" means exterior concrete slabs: driveways, walks, patios, porches and pool decks. They are usually a few inches thick, carry little weight and sit on the top layer of soil, the layer whose moisture changes most. That makes them more sensitive to soil movement than a house foundation.

In Oklahoma, the Oklahoma Geological Survey lists sidewalks and highways, along with foundations and utilities, among the things damaged when expansive soil swells after saturation from rain, lawn watering or sewer leaks ². More than 75% of the state has bedrock that can produce expansive soils ².

What causes can produce flatwork movement?

Swelling and shrinking clay

Expansive soil swells when wet and shrinks when dry ³. Swelling soils frequently cause distress in floor slabs, and water from a pool can differentially lift the adjacent pool deck ¹. Fissures in expansive soil can be up to about 20 centimeters (8 inches) wide and 4 meters (13 feet) deep ⁶.

Water and erosion

The U.S. Geological Survey lists subterranean erosion, such as piping, and water leakage from utilities among the causes of landslides ⁴. Swelling clays can crack concrete drainage ditches, and the voids that form can lead to piping and erosion ¹. Leaking pipes and pools are common sources of uneven moisture ¹.

Tree roots

Root growth can physically disturb the ground, which is often seen as damage to pavements and walls ³. Trees also dry clay; see tree-root desiccation settlement.

Does flatwork movement mean the house moved?

Engineering guidance on expansive soil recommends keeping soil moisture steady around a building and mentions surrounding it with concrete paving as one way to limit moisture changes ⁵. When flatwork next to the house settles or tilts toward it, rain can collect against the foundation instead; see water ponding near foundation and surface drainage and grading.

How do you document flatwork movement?

1. Note which way each slab has moved: lifted, sunk or tilted, and toward or away from the house.
2. Measure height differences at joints and cracks with a ruler or level.
3. Photograph with a ruler in view, and record the season and recent weather.
4. Look for voids at slab edges, downspouts discharging onto or under slabs, and nearby trees.
5. Include key points on an elevation survey if the house is being surveyed.

How is flatwork repaired?

Options matched to flatwork include slabjacking and polyurethane to raise settled slabs, void and compaction grouting, and drainage solutions to deal with the water. Lifting slabs that rose from swelling clay is not the same problem as raising sunken ones; see flatwork and exterior slabs.

Related

• Flatwork and exterior slabs
• Slabjacking and polyurethane
• Frost heave
• Erosion, undermining and washout voids
• Surface drainage and grading