Polyurethane Foam Jacking: How the Injection Process Works

Polyurethane Foam Jacking: How the Injection Process Works

Sunken driveway or patio? Polyurethane foam jacking lifts settled concrete in hours. Here is the injection process step by step, plus foam vs. mudjacking, costs, and durability.

Polyurethane foam jacking — also called slab jacking or polylifting — injects a two-part polyurethane foam beneath a sunken slab through small drilled holes. The foam expands, fills soil voids, and gently raises the concrete. Most jobs finish in hours, and you can drive on the slab the same day.

If your driveway has a lip where it meets the garage, or your patio slopes toward the house, the soil under that concrete has settled or washed out. Tearing out and repouring is the old answer — loud, messy, expensive, and it does nothing about the bad soil underneath. Foam jacking fills the voids and lifts the slab from below, usually for a fraction of replacement cost.

Homeowners ask us about this one a lot, so let’s walk through exactly what happens from the moment the crew arrives to the moment you park your car back on the driveway.

What Polyurethane Foam Jacking Actually Is

Strip away the trade names and the chemistry is simple. Two liquid components — a polyol resin and an isocyanate — meet in a mixing gun at the job site. The moment they combine, a reaction starts that turns the liquid into an expanding rigid foam, a lot like the foam in a can you might use around windows, but engineered to support thousands of pounds.

That expansion is the whole trick. As the foam grows, it does three jobs at once: it fills empty pockets under the slab, it compacts the loose soil around those pockets, and it pushes upward with enough controlled force to lift the concrete. The technician controls the lift by injecting in small bursts and watching the slab rise — often with a laser level — so the lift is gradual and even.

Once cured, the foam is a lightweight, waterproof, rigid material that will not wash out or rot — and it adds very little weight to ground that is already settling. A cubic foot of cured foam weighs roughly 2 – 4 pounds, versus 100-plus pounds for the same volume of mudjacking slurry. On soft Louisiana soils, that weight difference matters.

Why Concrete Settles in the First Place

Foam fixes the slab, but it helps to know why slabs sink, especially around Shreveport:

• Poorly compacted fill soil. New construction backfill that was never compacted right settles over the first few years, leaving voids under driveways and patios.
• Water erosion. Heavy Louisiana rains and misdirected downspouts wash soil out from under slabs, especially along driveway edges. (If this is your cause, pair the lift with drainage correction or it will happen again.)
• Expansive clay cycles. Our shrink-swell clay moves with the seasons. Repeated swelling and shrinking can open voids beneath concrete over time.
• Plumbing leaks. A slow leak under or near a slab erodes soil grain by grain until the concrete has nothing left to sit on.
• Tree roots. Roots draw moisture from soil, causing localized shrinkage and settlement near large trees.

The Injection Process, Step by Step

Here is what actually happens on job day. A typical residential foam jacking job — a two-car driveway section or a patio — takes 2 to 4 hours from arrival to cleanup.

Step 1: Assessment and Lift Plan

The crew walks the slab and maps the settlement: where it has dropped, how far (often 1 – 4 inches on residential jobs), and where the voids likely are. They check for the cause, too — if a downspout is dumping water under the driveway, they will tell you, because lifting without fixing the water is a temporary win. Injection points get marked in a grid pattern, usually 3 – 6 feet apart depending on the slab.

Step 2: Drilling Small Access Holes

Using a rotary hammer drill, the technician drills holes about 5/8 inch across — roughly the diameter of a dime — at each marked point. Compare that to mudjacking, which needs holes 1.5 – 2 inches wide: smaller holes, cleaner result, far less patching.

Step 3: Injecting the Foam

This is the main event. The injection gun goes into the first hole, and the two-part foam is pumped underneath in controlled bursts. Underground, the foam starts expanding within seconds — growing to many times its liquid volume — filling voids, compacting loose soil, and pushing upward. The technician moves hole to hole in sequence while a laser level on the slab tracks the rise in real time, down to fractions of an inch. The goal is a slow, even lift — an experienced operator can meet an existing edge like a garage floor within about a quarter inch.

Step 4: Monitoring the Lift

Lifting concrete is part science, part feel. Too much foam in one spot and the slab can crack or lift unevenly, so good crews inject, pause, measure, and move on — sometimes returning to an earlier hole for a final nudge. This is the step where experience shows, and it is why foam jacking is not a DIY project: the material reacts in seconds, and there is no undo button for an over-lifted slab.

Step 5: Patching and Cleanup

Once the slab is level, the injection holes get filled with a concrete patching compound and smoothed flush. The crew cleans up, and you are done. The foam reaches handling strength in about 15 – 30 minutes and full cure within a day — but in practice, you can usually walk on it within the hour and drive on it the same day.

Foam Jacking vs. Mudjacking: An Honest Comparison

Mudjacking (slab jacking with a cement-based slurry) has been around for decades and still works. But foam has taken over most residential work for good reasons. Here is the side-by-side:

Factor	Polyurethane Foam	Mudjacking Slurry
Hole size	~5/8 inch (dime-sized)	1.5 – 2 inches
Weight added	Very light (2 – 4 lbs per cubic ft)	Very heavy (100+ lbs per cubic ft)
Cure / use time	Drive on it same day	24 – 72 hours before full use
Water resistance	Waterproof, will not wash out	Can erode again if water returns
Lift precision	Fine control, small increments	Coarser, harder to fine-tune
Typical cost	Higher per job, but less material needed	Lower per job on large areas
Best for	Driveways, patios, sidewalks, pool decks on soft soil	Large commercial slabs, very thick concrete

On Louisiana’s soft, wet soils, foam’s light weight is the deciding factor for most homeowners. Pumping a hundred pounds of slurry per cubic foot onto soil that is already settling is asking the soil to hold up even more weight. Foam lifts without loading the ground. For a full cost breakdown of both methods, see our concrete leveling cost comparison: mudjacking vs. foam.

What Foam Jacking Can (and Can’t) Lift

Foam jacking is remarkably versatile on residential concrete:

• Driveways — the most common job; fixes the lip at the garage and trip hazards at joints
• Patios and pool decks — re-levels slabs that slope toward the house (a water problem) back to proper drainage slope
• Sidewalks and walkways — lifts settled sections that have become trip hazards
• Garage floors — can be lifted from inside or through the driveway approach
• Stoops and steps — small, precise lifts where replacement would mean demo and new pours

What it cannot do: foam will not fix a slab broken into many pieces, it will not fix a settling house foundation (that needs piers — different problem, different tool), and it cannot lift concrete pinned under a structure. A good contractor tells you when foam is the wrong tool. Our concrete leveling service page covers where foam fits in the bigger picture.

How Long Does Foam Jacking Last?

The foam itself is extremely durable — waterproof, rot-proof, and unattractive to insects. Once cured, the material will outlast the concrete sitting on it. Whether the lift lasts depends on the soil and water, not the foam. If the original settlement was a one-time event (poor compaction, a repaired plumbing leak), the lift is effectively permanent. If the cause is ongoing — uncorrected drainage washing soil out, or a still-active leak — the soil can move again around the foam. Fix the water first or alongside the lift.

In practice, on stable soil with the water issue addressed, foam lifts hold for many years — commonly a decade or more. Pelican’s foundation repair team evaluates the whole picture (soil, water, slab) before recommending foam, so you are not paying for a lift that the yard will undo.

The Louisiana Angle: Heat, Humidity, and Clay

A quick note for Shreveport-area homeowners: summer heat and humidity do not bother cured foam — it is closed-cell, waterproof, and rated far beyond anything Louisiana delivers. The local variable is always the clay, and foam’s light weight is a genuine advantage on expansive soils because you stabilize the slab without loading ground that already moves with the seasons. Pair the lift with good drainage and you have addressed both the symptom and the cause.

What Foam Jacking Costs

Pricing is usually based on how much foam the job needs and how far the slab has settled. For typical Shreveport-area residential work:

• Small jobs (a sidewalk section, a stoop, one patio corner): $500 – $1,200
• Mid-size jobs (a driveway section, a full patio): $1,200 – $3,500
• Larger jobs (long driveways, pool decks, multiple areas): $3,500 – $7,000+

Most companies have a minimum charge (commonly $500 – $800) because mobilizing the rig and material costs the same whether you lift one slab or ten. Compare that to tear-out and replacement at roughly $8 – $15 per square foot — a 400-square-foot driveway section can easily top $4,000 – $6,000, plus days without a driveway and a new slab sitting on the same unsettled soil. Foam usually lands at 30 – 50% of replacement cost.

One caution on quotes: if a price seems far below the ranges above, ask what foam is being used and how lift is measured. Cheap, low-density foam and “eyeball it” leveling are how bad foam jobs happen. For patios specifically, our guide to concrete leveling for Louisiana patios walks through that exact project.

Frequently Asked Questions

How does polyurethane foam jacking work?

Two liquid components are mixed at the job site and injected beneath the sunken slab through dime-sized holes. The mixture expands into a rigid, waterproof foam that fills voids, compacts loose soil, and lifts the concrete back to level. A technician controls the lift in small increments while monitoring with a laser level.

How long does foam jacking take?

Most residential jobs take 2 – 4 hours. The foam supports weight in about 15 – 30 minutes, so you can usually walk on the slab within the hour and drive on it the same day.

Is foam jacking better than mudjacking?

For most residential work on soft soils, yes: smaller holes, almost no added weight, minutes to cure, and it will not wash out. Mudjacking still suits very large commercial slabs. Our mudjacking vs. foam cost comparison breaks down when each wins.

How much does polyurethane foam jacking cost?

Typical residential jobs in the Shreveport area run $500 – $1,200 for small lifts (sidewalk sections, stoops), $1,200 – $3,500 for mid-size jobs (driveway sections, patios), and $3,500 – $7,000+ for large areas. That is generally 30 – 50% of the cost of tearing out and repouring.

Will the foam wash away in heavy Louisiana rain?

No. Cured polyurethane foam is closed-cell and waterproof — water runs around it, not through it. But if runoff caused the original settlement, fix the drainage too, or water keeps eroding the soil around the foam.

Can foam jacking fix my settling house foundation?

No — and be wary of anyone who says it can. Foam jacking lifts non-structural concrete like driveways, patios, and sidewalks. A settling house foundation needs steel piers or helical piers driven to stable soil, which is a different repair entirely. If your home itself is settling, get a foundation inspection, not a foam quote.

Is polyurethane foam safe around my home?

Yes. The components react and cure within minutes, and the finished foam is inert — it does not off-gas, leach, or break down in soil. It is widely used under homes, schools, and commercial buildings. The U.S. EPA regulates the raw chemical components for worker handling, which is one more reason this is a pro-only job, not DIY.

How do I know if my concrete can be foam jacked?

If the slab is mostly intact, has settled 1 – 4 inches, and is not pinned under a structure, it is probably a candidate. Slabs broken into many pieces usually need replacement. A free inspection with measurements gives you a straight answer.

Pelican Foundation Repair
6118 Fairfield Ave, Shreveport, LA 71106, USA
318-585-2003
https://foundationrepairshreveport.com/