Fill the Empty Space Under Your Slab Before It Sinks

Most voids in this region come from soil that leaves while the slab stays put. Expansive clay shrinks during dry summers and pulls away from the underside of the concrete. Loess and silty soils wash out when roof runoff, a leaking downspout, or poor grading funnels water along a slab edge. And backfill that was never compacted well keeps settling for years after a home is built. Epp Foundation Repair sees all three across Nebraska, Iowa, Kansas, and Missouri, often together on the same slab.

Epp Foundation Repair drills penny-sized ports through the slab and pumps in a two-part polyurethane as a liquid. The two parts react at the gun and expand to many times their volume in seconds, flowing into every connected pocket under the concrete and then firming up. Because it is a mid-soil injection, the foam reaches about 4 feet down, fills the open void, and presses lightly into loose soil seams. The cured foam carries several thousand pounds per square foot and does not absorb water.

Filling the void gives the slab solid contact with the ground again, which stops it from flexing and dropping over open space. That is the main protection against future sinking. Our goal is permanent stabilization, and some lift may be possible depending on conditions, but void filling is not a promise to raise the slab back to grade. If a footing under the slab is still moving, that has to be addressed first, and Epp will tell you that at the inspection rather than foam over a moving problem.

The polyurethane Epp Foundation Repair uses does not break down, rot, or absorb water, so the fill itself is built to last for the life of the slab. What can change is the soil around it. If the original water problem, a leaking downspout or bad grading, keeps washing soil out, new voids can open in adjacent areas. Solving the water source is part of a lasting fix, which is why the crew traces where water has been entering before they inject.

Yes. Driveways, garage floors, patios, sidewalks, and the slab under a finished basement are common void-filling jobs. The foam injects through small ports, so there is no tear-out, and the slab takes foot traffic right away and vehicle traffic the same day. The cured foam carries vehicle loads easily. Epp Foundation Repair confirms the concrete is sound first, because foam supports a slab but cannot rebuild concrete that is already broken into pieces.

Void filling is usually priced by the area treated and how much foam the pockets take, since a hollow you cannot see from the surface may be larger than it looks. A Customized Repair Estimate after an on-site inspection reflects your scope. Dave Epp does not price a slab he hasn't seen, because the void volume is the variable that moves the number.

A void does not fill itself, and the unsupported span only gets wider as more soil washes out or shrinks. The slab bridges the gap until it cannot, then it cracks or drops, often under the weight of a vehicle or a hard freeze. Once the concrete cracks, foam can still support the pieces, but you have lost a slab that could have been saved whole. Epp Foundation Repair has seen sound slabs that needed a simple fill turn into replacement jobs over a season or two of waiting.