Fix it while the slab still looks fine.
A void is a gap the concrete is bridging. Concrete void filling, done before the slab finds out, is the cheapest version of this repair anyone will ever offer you.
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What to know about concrete void filling, and when it's the right call.
Void filling and slab lifting are the same process stopped at different points. Two liquid polyurethane components stay inert until they meet at the injection nozzle, react within seconds, and expand to many times their liquid volume, generating pressure as they go. The expanding resin follows the path of least resistance, which is the void, and fills it completely, including the fingers and channels that a slurry hose could never reach. As it presses outward at the edges it compacts the loose, disturbed soil that the erosion left behind, turning a soft zone into part of the new bearing surface. In a lifting project, continued injection past that point is what raises the slab. In a void filling project, that is where the work stops: the crew watches for the first movement at the surface and takes the pressure off, so the gap is gone and the elevation is unchanged. Within minutes the material cures into a rigid, closed cell base that does not absorb water, does not compress under traffic, and does not shrink back as it sets. The drilled ports are patched with concrete, and there is nothing to see afterwards, which is the point: the repair happened before there was any damage to show.
The symptoms that usually lead to concrete void filling are on the concrete leveling problem signs page, alongside the other signs that point to the same underlying cause.
How we install concrete void filling.
Sound the slab and map the void
Tapping across the concrete changes tone where it has separated from the soil, and tracing that boundary draws the void's footprint from above. Elevations are logged at the same time so we know whether the slab has moved yet.
Find the water that made it
Downspouts, irrigation, grade and joints are traced, because a void filled without closing its source inherits the same erosion that created it, and a garage slab losing its base is the clearest example of it.
Drill small injection ports
Ports about five eighths of an inch across are placed to reach the whole footprint, which is why the sounding comes first rather than a standard grid. On a slab that has already dropped the same ports serve the slab jacking lift as well.
Inject to full, then stop
Expanding polyurethane fills the gap and densifies the soil at its edges. Injection stops at the first sign of movement at the surface, because the job is support rather than lift.
Patch and verify
Ports are patched, the slab is sounded again to confirm the drum note is gone, and final elevations are compared against the starting survey. The readings go into your written findings the same way every other concrete leveling job here is recorded.
Concrete Void Filling on a real project.
A void is a gap the concrete is bridging. Concrete void filling, done before the slab finds out, is the cheapest version of this repair anyone will ever offer you.
Care and expertise from a team that's been doing this since 2011.
When the fix is concrete void filling, the installer matters as much as the method. Dalinghaus crews handle foundation, concrete, and crawl space work across California, Arizona, and Nevada, and nothing else.
Foundation repair, concrete leveling, and crawl space repair are our entire focus. Not a sideline.
More than 2,000 projects on the clay and desert soils of California, Arizona, and Nevada since 2011.
CSLB License #983851 in California, ROC #330307 in Arizona, and License #0089738 in Nevada. Look us up with the state before we ever set foot on your property.
Warranty terms come in writing with every proposal, and the terms that apply to your job are stated in that job's paperwork. Ask your project specialist during the free evaluation.
Answers to common questions about Concrete Void Filling.
Don't see your question here? Our team is happy to help. Reach out anytime.
Sound. Tap or walk across the slab and listen for a change from a dull thud to a hollow drum note. That change is the concrete no longer being in contact with the soil underneath it. A slab can sound hollow across a surprisingly large area while still measuring dead level, which is exactly the stage at which this repair is cheapest and least disruptive.
Other concrete leveling solutions we install.
Every solution is engineered for a specific soil profile and failure mode. Browse the full toolkit.
Concrete Grinding
Where a slab has stopped moving and one edge stands proud, shaving it flush removes the hazard in a visit. Where the slab is still moving, it only resets the clock.
Learn more
Polyjacking
Polyjacking injects expanding polyurethane under a sunken slab, raising it in minutes through coin sized holes. Light on the soil, hard under the load.
Learn more Polyurethane Foam Injection
Polyurethane foam injection restores the support your concrete lost: it fills the gap, densifies the soil, and lifts the slab back to grade, all through coin sized holes.
Learn more
Slab Jacking
Slab jacking lifts sunken concrete from below, through small holes, back to the level it was poured at. Here is how the method works and how we choose the material.
Learn moreFrom free evaluation to installed concrete void filling.
How a concrete void filling project moves from diagnosis to completed installation.
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Get your repairs.
Our crews complete the work on schedule, with the findings and scope in writing from the first visit.
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