How to Fix a Sinking Driveway: Mudjacking vs Polyurethane Foam

Why Your Driveway Is Sinking—and Why You Should Act Fast

A dip in the pavement is more than an eyesore; it’s a warning. Left alone, a sinking driveway funnels water toward your foundation, cracks widen, and slabs can tilt so far they become a trip hazard. The good news: you rarely have to tear everything out. Two proven lifting methods—mudjacking and polyurethane foam injection—can restore a level surface in hours, not days.

Below you’ll learn exactly how to fix a sinking driveway, what each repair costs, how long it lasts, and which option fits your soil, climate, and budget.

Option 1: Mudjacking (Slabjacking)

Mudjacking has been around since the 1930s. Contractors drill 1⅛–1½ in. holes through the slab and pump a cement-rich slurry underneath. Hydraulic pressure lifts the concrete back to grade, then the slurry hardens into a stable fill.

Step-by-Step: How Mudjacking Works

1. Diagnose voids. A pro taps the slab or uses a ground-penetrating radar to map hollow spots.
2. Drill access holes. Two to four holes per 100 sq ft is typical.
3. Mix the slurry. Portland cement, sand, and water—sometimes bentonite clay or fly ash—for flowability.
4. Pump and lift. Pressure gauges prevent over-lifting; crews watch the slab edge or use laser levels.
5. Patch holes. Cement grout plugs the holes; the surface is ready for cars the same day.

Pros of Mudjacking

• Lowest upfront cost—usually 25–50 % less than foam.
• Environmentally friendly slurry (mostly natural minerals).
• Excellent compressive strength (2 000–4 000 psi) for heavy vehicles.

Cons of Mudjacking

• Heavier material (100–110 lbs per cu ft) can re-settle if underlying soil is weak.
• Larger drill holes are visible after patching.
• Requires dry weather; slurry can freeze before it sets in cold climates.
• Not ideal for slabs thinner than 4 in. (too easy to crack).

Option 2: Polyurethane Foam Injection

Sometimes called “polyjacking” or “foam jacking,” this method injects a two-part liquid that expands into a high-density foam. The foam cures in minutes, weighing only 2–4 lbs per cu ft yet supporting 7 000+ psi compressive strength.

Step-by-Step: How Polyurethane Foam Works

1. 5⁄8-in. holes are drilled—about the size of a dime—through the slab.
2. Ports are inserted to deliver the foam in controlled lifts.
3. Dual-component gun mixes resin & catalyst; chemical reaction starts instantly.
4. Slab rises as foam expands 15–25 times its liquid volume.
5. Holes are patched and the driveway is drivable in 15 minutes.

Pros of Polyurethane Foam

• Lightweight: won’t burden loose or clay-rich soils.
• Moisture-proof: seals underside of slab, preventing freeze-thaw spalling.
• Smaller holes = nearly invisible patches.
• Fast cure—perfect for busy households or HOA deadlines.

Cons of Polyurethane Foam

• Higher material cost—expect 35–60 % more than mudjacking.
• Not all foams are equal; low-grade products can shrink or off-gas.
• Requires experienced techs; over-foaming can lift slabs too high.
• Recyclability is limited compared with natural cement slurry.

Cost Comparison: What Homeowners Pay in 2024

Prices vary by region, slab size, and how far the concrete has dropped. The figures below are typical for a standard two-car driveway section (≈ 200 sq ft) lifted 2–3 in.

Mudjacking Costs

• Residential: $4–$6 per sq ft ($800–$1 200 total).
• Additional sections beyond the first 200 sq ft often drop to $3 per sq ft.

Polyurethane Foam Costs

• Residential: $6–$10 per sq ft ($1 200–$2 000 total).
• Price includes premium hydro-insensitive foam and 1-year workmanship warranty.

Rule-of-thumb: If your driveway is 25+ years old and you plan to replace it within five years, mudjacking delivers the best ROI. For newer concrete or if you need precision leveling (garage approach, pool deck), polyurethane foam is worth the upcharge.

Which Repair Lasts Longer?

Both methods can deliver 5–10 years of service when coupled with proper drainage. Polyurethane has a slight edge because it:

• Repels water, preventing future soil softening.
• Adheres to the slab, locking out erosion.

Mudjacking slurry can erode if downspouts discharge directly beside the slab. Install gutter extensions ($15 each) and keep cracks sealed to max out either warranty.

Can You DIY a Sinking Driveway?

Short answer: not really. Both techniques need industrial pumps, specialized material, and real-time leveling tools. Online “foam kits” cost $300–$600 but rarely exceed 10 lbs of foam—enough for a sidewalk corner, not 400 sq ft of driveway. Mistakes cure in minutes; correcting an over-lift requires costly grinding or replacement.

What you can do yourself:

• Mark settling areas with chalk and photograph them for contractors.
• Clear cracks of weeds and seal with backer rod & polyurethane joint sealant ($30).
• Reroute downspouts at least 5 ft from the slab.

How to Choose the Right Contractor

1. Verify insurance. Ask for a certificate showing general liability and workers’ comp.
2. Demand references within a 10-mile radius—drive by and inspect older jobs.
3. Compare warranties. One-year minimum; three years is common for foam.
4. Get load-bearing data. Reputable providers will cite compressive-strength lab results.
5. Ask about cleanup. Foam overspray can stain brick or siding; pros mask adjacent surfaces.

After the Lift: Maintenance Tips to Prevent Future Settling

• Seal expansion joints every 2–3 years to block water infiltration.
• Keep vehicles under 12 000 lbs on residential driveways; heavy loads stress edges.
• Slope landscaping so soil around the driveway crowns ¼ in. per foot away from slab.
• Install a French drain if you notice standing water after rain.

Frequently Asked Questions