Void Filling Under Concrete
Empty spaces beneath concrete can lead to settling, cracking, uneven surfaces, and eventually expensive repairs. Pro Polyjacking provides professional void filling under concrete throughout the Kansas City area using lightweight polyurethane foam that expands beneath the slab, fills hidden gaps, and helps stabilize the supporting soil. Unlike traditional mudjacking, our foam void filling process adds very little additional weight beneath the concrete while creating durable support where it is needed most.
"WHAT IS IT?"
Why a Void Under a Concrete Slab Can Become a Serious Problem
A void under a concrete slab develops when the soil or material that originally supported the concrete moves, settles, erodes, or contracts, leaving an unsupported space between the ground and the slab. This can be especially troublesome in the Kansas City area, where changing moisture levels, shifting soils, heavy rain, drainage problems, and seasonal freeze-thaw conditions can continually affect the ground beneath driveways, sidewalks, patios, garage floors, commercial slabs, and other concrete surfaces. Once support is lost, the concrete must span the empty area on its own. As vehicles, foot traffic, equipment, and the weight of the slab itself continue placing pressure on that unsupported concrete, sections can begin to settle, tilt, crack, or break. Water entering beneath the slab can make the situation worse by moving loose material and enlarging the existing void. Professional concrete void filling addresses the problem below the surface by filling these empty spaces and restoring support beneath the concrete before additional settlement or damage occurs.
"WHen to MUDJACK?"
Why Polyjacking Is Better for Concrete Void Filling
Traditional mudjacking attempts to fill the space beneath concrete by pumping a heavy slurry made from water, soil, and cement underneath the slab. While that material can initially fill a void and raise concrete, it also places considerably more weight on the same underlying soil that allowed the void or settlement to develop in the first place. Pro Polyjacking uses high-density polyurethane instead. The polyurethane begins as an injectable material and rapidly expands beneath the concrete, allowing it to spread through empty spaces and provide support without loading unstable soil with a large amount of additional weight. Pro Polyjacking reports polyurethane at approximately 2–4 pounds per cubic foot compared with roughly 100 pounds per cubic foot for traditional mudjacking material.
That difference makes foam void filling particularly well suited for Kansas City properties. Polyurethane foam is hydrophobic, meaning it does not rely on a soil-based mixture that can be eroded or washed away as water moves beneath the concrete. The expanding foam can also reach irregular gaps beneath a slab, helping with both void filling under concrete and stabilization of loose material surrounding the affected area. Because the foam expands quickly, technicians can precisely inject material where support is needed rather than filling the area with a large volume of heavy slurry.
Polyjacking also requires substantially smaller access points. Traditional mudjacking commonly requires holes approximately 1⅝ to 2 inches across, while Pro Polyjacking uses approximately dime-sized injection holes. Once the polyurethane has been injected, the holes can be patched with much less visible disruption to the existing surface. The foam expands and cures rapidly as well, allowing many concrete surfaces to return to use much sooner than with mudjacking. For homeowners and businesses looking for concrete void filling that minimizes disruption while providing lightweight, water-resistant support, polyurethane offers a modern alternative designed for the conditions beneath the slab—not simply a temporary way to pack more material underneath it.
Frequently Asked Questions About Void Filling Under Concrete
What causes a void under a concrete slab?
A void under a concrete slab can develop when supporting soil settles, contracts, erodes, or is displaced by water. Around Kansas City, seasonal moisture changes, drainage problems, shifting soil, and freeze-thaw cycles can all contribute to movement beneath concrete. Once soil pulls away from the slab, the unsupported space can gradually become larger and eventually contribute to sinking or cracking concrete.
How does foam void filling work?
Foam void filling uses polyurethane that is injected through small holes drilled through the concrete. Once beneath the slab, the polyurethane expands rapidly, flowing into available spaces and filling the void. As it expands and hardens, the foam provides support beneath the concrete and can help stabilize loose surrounding material. When necessary, controlled expansion can also be used to raise settled sections of concrete toward their proper position.
Is polyurethane better than mudjacking for void filling under concrete?
Polyurethane offers several advantages over traditional mudjacking for void filling under concrete. The foam is dramatically lighter than mudjacking slurry, requires much smaller injection holes, cures rapidly, and is hydrophobic. These characteristics are especially valuable where weak soil or water movement contributed to the original void because the repair adds minimal additional weight and the polyurethane itself is resistant to being washed away.
Can concrete void filling prevent my slab from sinking?
Professional concrete void filling can restore support where empty spaces have developed beneath a structurally sound slab, reducing the unsupported areas that can contribute to settlement and cracking. Polyurethane can also help stabilize loose material beneath the concrete. However, drainage problems and other conditions contributing to soil movement should also be addressed whenever possible to reduce the risk of future settlement. If the concrete itself is severely deteriorated, broken into many pieces, or otherwise structurally failing, replacement may be more appropriate than lifting or void filling.