Sinking Concrete Slab Repair Cost: Mudjacking vs Foam

A sinking concrete slab — driveway, patio, garage floor, or walkway — can be lifted back to level with either mudjacking ($3 to $9 per square foot) or polyurethane foam injection ($5 to $25 per square foot). This is a different, much less expensive problem than a sinking foundation wall; if your foundation itself is settling, see our foundation piers guide instead.

Cost and performance comparison

For a typical single slab project (a sidewalk section or small patio), polyurethane foam injection often totals $500 to $4,000, while mudjacking a similar area typically costs less per square foot but follows the wider ranges above depending on slab size.

Why the price gap exists

Polyurethane foam can cost up to 4 times more per square foot than mudjacking. The premium buys you a much faster cure time (traffic-ready in about 15 minutes versus 24-48 hours for mudjacking) and a dramatically lighter material — polyurethane weighs 2-4 lbs per cubic foot versus 100+ lbs for mudjacking's cement-based slurry. That weight difference matters because mudjacking adds significant new load to a subgrade that may already be struggling to support the slab, which is part of why some slabs sink again after mudjacking sooner than after a foam repair.

Which one makes sense for your project

• Choose mudjacking if budget is the primary concern and the slab isn't in an area with known poor or unstable subgrade — it's a well-established, lower-cost method for straightforward sinking.
• Choose polyurethane foam if you need the area back in use quickly (driveways, walkways with daily foot traffic), the subgrade is already soft or unstable, or you're trying to minimize the risk of the slab sinking again.

When it's not just the slab

If a driveway or patio slab keeps sinking repeatedly even after repair, or if the sinking extends to the foundation itself rather than a standalone slab, the underlying cause may be broader soil or drainage issues worth a full foundation assessment — see the foundation repair cost guide for that bigger picture.

Prices on this page are researched ranges compiled from multiple public contractor-pricing sources, not quotes from us or a guarantee of what you will pay. Actual costs vary by region, material choice, and job complexity — always get itemized quotes from licensed local contractors before committing to a project. See How We Price for our sourcing methodology.

Frequently Asked Questions

Can mudjacking or foam fix a foundation, not just a slab?

No — mudjacking and polyurethane foam are designed for flatwork slabs (driveways, patios, walkways, garage floors) that have sunk due to soil settling beneath them. A foundation wall that's settling needs a different solution, typically piers or underpinning, because it's load-bearing and structurally different from a flatwork slab.

How long does a mudjacked or foam-lifted slab stay level?

Both methods can last many years if the underlying cause of the original sinking (poor drainage, soil erosion, or unstable fill) is also addressed. If the root cause isn't fixed, either method can see the slab sink again over time, though foam's lighter weight makes it somewhat less likely to accelerate a repeat sink.

Is polyurethane foam injection safe for the environment?

The polyurethane used in slab lifting is a closed-cell, inert material once cured, and is generally considered safe for residential use around foundations and landscaping. If you have specific environmental concerns, ask your contractor about the specific product they use.

Why did my slab sink in the first place?

Common causes include soil erosion from poor drainage, soil compaction that wasn't done properly during original construction, tree root removal leaving a void, or naturally expansive/contractive soils in your region. Understanding the cause helps determine whether a repair will hold long-term or whether drainage improvements should be part of the fix.