Last Updated on October 20, 2026 by Umar Farooq
Polyurethane foam under pavers can raise a sunken patch, but it is a concrete-slab technique borrowed for a surface that is not a slab, and it leaves the two things that made the pavers sink untouched: the base and the water. If your pavers dropped because sand or stone washed out, foam lifts the symptom and the cause goes on working underneath it. The first job is to find out why they sank. Then decide whether lifting and relaying them, which costs a rented compactor and an afternoon, is the better call.
I went looking for any independent test of foam on sand-set pavers and found none. What exists is vendor pages about slabs and one consumer article about the problems. So this page is what those say, plus the ICPI numbers any lift has to meet.
What polyurethane foam under pavers does, and where it comes from
The method comes from slab repair. A crew drills small holes through the sunken concrete, injects polyurethane, and the foam expands under the slab and pushes it up. One concrete-leveling contractor says the foam cures, expands and hardens in about 15 minutes after injection, and that it is lighter than the grout used in mudjacking, so it loads the weak soil less (ESOG). Those are company claims, and the page says nothing about pavers.
Hunker, writing for consumers, accepts that a can of spray foam can lift a paver in principle, since pros lift slabs this way (Hunker). Then it lists why it usually goes badly.
Foam or relay: what changes under the pavers
A paver patio is not one piece. It is hundreds of small units on one inch of loose bedding sand, held together by joint sand and an edge restraint. CMHA's guide spec says the screeded sand must not be disturbed. A slab rises as a single plate. Pavers have to rise together and stop at the same height, and ICPI allows at most 1/8 inch of lippage between neighbours on a pedestrian route (ICPI Tech Spec 2). That is my inference, not a published test: a pump can raise a slab, but landing a few dozen separate units within 1/8 inch is a harder target.
The downsides on sand-set pavers
- Holes in the pavers. Hunker says you have to drill several holes through the pavers to get foam under them, and that the tools can cost more than the traditional repair. The alternative is injecting through the joints, which I could not find described for pavers anywhere.
- Guesswork. Pros use pumps and gauges. A spray can does not, so a perfectly level result is unlikely.
- The cause stays. Foam does not address why the pavers sank. If the washout continues, so does the sinking.
- Drainage gaps. Hunker warns that if poor drainage caused the problem, foam can leave gaps that invite erosion.
- Mess. Foam can expand out of the holes and onto the pavers.
I found no independent durability data on foam under pavers. The longevity claims online come from companies that sell the service.
Ask why they sank before you pick a fix
A dip under a downspout is washout. A dip along an edge is usually a failed restraint, covered in paver edges sinking. A dip that appeared in the first year may be ordinary settling after installation. Foam helps none of these on its own. The washout version is explained in paver base washout.
Do the hose test first. Run water over the dip and watch where it goes. If it pools or runs into the base, fix that, then fix the pavers.
The one case where foam is reasonable
If the pavers sit on a concrete slab and the slab is what sank, foam is doing the job it was designed for. A-1 Concrete Leveling describes the same two options for a settled slab: leveling, or piers when the settling is too severe (A-1 Concrete Leveling). Pavers glued or laid over a slab are covered in pavers over concrete.
If you still want a quote, ask the contractor:
- How many paver jobs, not slab jobs, have you done?
- Where do the holes go, through the pavers or the joints?
- How will you keep neighbours within 1/8 inch?
- What fills the void if the base itself has eroded?
- What does the warranty say about a repeat dip?
If the answers are vague, you have your answer.
What does not work
- A hardware-store spray can. Drilling, guesswork and mess, per Hunker.
- Sweeping sand into the joints. It does not reach the void.
- Foam as a drainage fix. It is not one, and Hunker says it can make erosion worse.
Lift, fix, relay
For a patch of sunken pavers, the cheaper option is the one the pavers were designed for: lift them, rebuild the base in thin lifts, screed one inch of sand, and lay them back. How to fix sunken pavers walks through it. I would not pay anyone to hide a dip I had not diagnosed.
FAQ
Can you use spray foam to lift sunken pavers?
In principle, yes. Hunker says a spray can can lift a paver, but you have to drill holes through the pavers, you cannot control the amount, and the result is rarely level.
How long does polyurethane foam take to cure?
One concrete-lifting company says about 15 minutes after injection before it expands and hardens. Treat that as a vendor figure for slabs.
Will foam stop pavers from sinking again?
Only if the cause is not still active. Foam does not fix drainage or a failed edge restraint.
Is foam lifting better than mudjacking for pavers?
The vendor claim is that foam is lighter than mudjacking grout. I found no comparison on pavers.
Does foam lifting affect my paver warranty?
I found no warranty text that addresses it. Read your installer's and manufacturer's terms before drilling anything.
Foam raises the dip, and only the base fixes it
If a crew quotes you foam, ask the five questions above and the hose test. If the base is the problem, you are going to dig anyway, and a bag of sand costs less than an argument about holes in your pavers.
