Void filling under concrete slabs
Hidden voids under your concrete are the #1 reason slabs sink. We fill them with expanding polyurethane foam before the slab cracks, drops, or fails.
How it works
Voids form under concrete slabs from soil washout (downspouts, irrigation, plumbing leaks), poor original compaction, or freeze-thaw soil contraction. They are silent — until the slab above them suddenly drops or cracks. We locate voids using probing, GPR (ground-penetrating radar) on commercial jobs, or visual cues like hollow-sounding concrete and edge gaps. Polyurethane foam is then injected through small holes to fully fill and stabilize the cavity. The result: no more progressive settlement, no more sinkholes under driveways or garages.
Cost
Residential void filling typically runs $400–$1,200 depending on void size and number of injection points. Commercial and industrial void filling is quoted per cubic foot of foam.