Your Concrete Patio Is Sinking on One Side — Here Are Your Leveling Options

A patio that slopes toward the house, ponds water after rain, or leaves a trip step at one edge is almost always a slab that has settled — the soil or fill underneath it has compressed, eroded, or washed away, and one section of concrete has dropped with it. The short answer: most sunken patios can be lifted back into place without tearing them out, using either mudjacking or polyurethane foam injection, and replacement is only the right call when the slab itself is badly cracked or broken apart.

Why one side sinks

Concrete is heavy and rigid, so it follows whatever is underneath it. The usual culprits are poorly compacted fill soil from when the patio was poured, soil that erodes when downspouts or surface water run underneath the slab, tree roots that decay and leave voids, or plumbing leaks that wash soil away. A slab that sinks slowly over years usually means gradual soil compaction; one that drops suddenly after a heavy rain or a leak often means a void has opened up underneath.

Before you fix the slab, find the cause. If a downspout dumps water right at the patio edge, or the grade slopes toward the slab, lifting the concrete without fixing the water problem just buys time until it sinks again. Redirect downspouts, regrade the soil away from the patio, and fix any leaking hose bibs or irrigation lines first.

Option 1: Mudjacking (slabjacking with cement grout)

Mudjacking pumps a cement-based slurry under the sunken slab through holes drilled in the concrete, filling the void and lifting the slab as the mixture builds up. It is the older, well-proven method, and it typically costs less than foam lifting — roughly $500 to $1,500 for a typical patio section, depending on size and how far it has dropped.

The trade-offs: the slurry is heavy, so on soft or weak soil it can settle again over time, and the drill holes are larger (usually 1 to 2 inches) and need patching. It also takes longer to cure — usually a day before the patio can take full use. Mudjacking works best on larger, thicker slabs over reasonably firm soil.

Option 2: Polyurethane foam lifting

Foam lifting injects an expanding polyurethane foam under the slab through small holes (about the size of a dime). The foam expands, fills voids, and lifts the slab with precise control, and it cures within minutes, so the patio is usually usable the same day. Typical cost runs roughly $800 to $2,000 for a patio section.

Foam is lighter than cement grout, so it adds almost no weight to weak soil, and the small holes are nearly invisible after patching. The main downside is cost — it usually runs more than mudjacking — and it is less forgiving if the slab needs a very large lift. For a patio that has sunk a few inches on one side, foam is often the cleanest option.

Option 3: Full replacement

Replacement means breaking out the old slab, fixing the base properly (compacted gravel, correct drainage), and pouring new concrete. It is the most expensive option — typically $2,000 to $5,000 or more for a patio — and the most disruptive, but it is the right call when the slab is cracked through in multiple places, shattered into pieces, or so thin and deteriorated that lifting would just raise a broken slab. Replacement also lets you fix the base and drainage properly in one job, which matters if the original base was the problem.

What to check before you hire

Get quotes that specify how much lift is planned and how the contractor will handle drainage afterward. Ask whether the bid includes sealing the joints and cracks after lifting — open joints let water back underneath, which restarts the whole cycle. And be wary of any quote that skips the cause: a contractor who lifts the slab without asking where the water goes is selling a repeat job.

A small drop — under half an inch with no ponding — can sometimes wait, or be handled with a concrete grinder or a surface-leveling compound at the joint. But a drop of an inch or more, water pooling against the house, or a visible trip hazard should be fixed, both for safety and because water against the foundation causes bigger problems than a patio.

On ZIP Pros — "Pros in your ZIP" — describe the problem once and get free quotes from local pros, with real starting prices shown up front. Mention how far the slab has dropped and whether water ponds against the house — that tells the pro which lifting method fits.