Fill Voids Under Concrete
Voids beneath concrete slabs can lead to serious structural problems if they are not addressed. These empty spaces often develop when soil erodes, settles, or washes away beneath the concrete. When the slab loses support underneath, it can begin to crack, sink, or become unstable.
STL Polyjack provides void filling in St. Louis, MO using advanced polyurethane foam injection. This process fills empty spaces beneath concrete slabs and stabilizes the soil underneath. By restoring support below the slab, void filling helps prevent future settlement and protects the concrete structure above.
Why Voids Form Beneath Concrete
Concrete slabs rely on solid soil support underneath. When that support weakens or disappears, empty spaces can develop beneath the slab.
Common causes include:
- Soil erosion caused by water runoff
- Poor soil compaction during construction
- Water infiltration beneath the slab
- Natural ground settling over time
- Drainage issues around the property
When voids form, the concrete above them may begin to shift or crack. Filling these empty spaces helps restore stability and prevent further damage.
Signs You May Have Voids Beneath Concrete
Voids beneath concrete are not always visible right away, but there are several signs that may indicate the problem.
You may need void filling if you notice:
- Hollow sounds when walking on concrete
- Cracks forming in slabs or concrete surfaces
- Concrete beginning to sink or tilt
- Gaps appearing beneath the slab edges
- Water pooling around the concrete
- Uneven or unstable surfaces
If these issues continue, the slab may settle further and create larger structural concerns.
Voids beneath concrete can affect many different areas of a property. In some cases, void filling is needed before lifting the slab. Saint Louis Polyjack frequently performs void filling alongside services such as driveway leveling, walkway and sidewalk leveling, and pool deck leveling to stabilize the ground beneath the concrete.
Free Concrete Leveling Estimate
Customers can also send photos of the problem area for a faster quote.
Why Property Owners Choose Saint Louis Polyjack
Serving St. Louis, Sunset Hills, Fenton, Kirkwood, Ballwin, Chesterfield, and surrounding communities.
Our Fix: Polyurethane Void Filling
Saint Louis Polyjack uses polyurethane foam injection to fill empty spaces beneath concrete safely and efficiently. Instead of removing the slab, our process restores support underneath by injecting expanding foam into the void.
Our process works in three simple steps:
1. Drill Small Access Holes
Small holes are drilled in the slab so the foam can reach the empty space beneath the concrete.
2. Inject Expanding Polyurethane Foam
High-density foam is injected below the slab. The material expands to fill the void and stabilize the surrounding soil.
3. Patch the Holes and Finish the Repair
Once the void is filled and the slab stabilized, the holes are patched neatly and the repair is complete.
Benefits of Void Filling
Void filling provides several advantages compared to ignoring the problem or replacing the concrete.
Some of the main benefits include:
- Restores support beneath concrete slabs
- Helps prevent future settling
- Stabilizes weak soil beneath the slab
- Fast repair that typically takes only a few hours
- Minimal disruption to the surrounding property
- Helps extend the life of existing concrete
By filling empty spaces beneath the slab, this repair helps protect the structure above and prevent additional damage.
Why Choose STL Polyjack
When concrete starts to sink or settle, choosing the right contractor matters. STL Polyjack brings over a decade of experience and more than 1,200 completed lifts across the St. Louis area. We focus on fixing the root cause—not just the surface—using advanced polyurethane foam injection to lift and stabilize concrete without the cost and disruption of replacement. When you work with our team, you can expect:
- Over a decade of hands-on experience
- 1,200+ concrete lifting projects completed locally
- Polyurethane foam designed for long-term support
- Minimal disruption to your home or business
- Completed in hours, not days, with same-day use
- Honest evaluations and straightforward recommendations
- Repairs backed by a 5-year warranty
Whether the project involves a residential driveway, uneven sidewalk, patio, commercial slab, or structural repair, our goal is to deliver a repair that restores safety, stability, and confidence in your concrete surfaces.
FAQs – Void Filling
Clear answers about how void filling works and why stabilizing the soil beneath concrete is important.
Void filling is a repair method used to fill empty spaces beneath concrete slabs. Saint Louis Polyjack uses expanding polyurethane foam to fill these spaces and restore support beneath the slab.
Voids usually form due to soil erosion, water movement, or poor soil compaction during construction. Over time, these conditions can wash away soil and leave empty space beneath the slab.
Yes. Filling the void restores support beneath the slab and helps prevent further settlement. In some cases, void filling is combined with services like concrete leveling to lift the slab back into position.
Most void filling projects can be completed in just a few hours depending on the size of the area and the amount of space beneath the slab.
Yes. High-density polyurethane foam expands beneath the slab and forms a strong support structure that stabilizes the concrete above it.
Yes. Void filling is often performed alongside services such as driveway leveling, garage floor leveling, and patio leveling when slabs have lost support underneath.
Yes. The polyurethane material stabilizes the soil and fills empty spaces beneath the slab, helping create a durable and long-lasting repair backed by Saint Louis Polyjack’s 5-year warranty.
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Areas We Serve
STL Polyjack proudly serves homeowners, businesses, and property managers across the St. Charles and St. Louis area. With over a decade of experience, we provide polyurethane concrete leveling, lifting, and structural repair solutions that restore sinking concrete without the cost of replacement. From driveways and sidewalks to warehouse floors and parking lots, we keep properties safe, level, and stable.
Serving St. Louis & Surrounding Communities
- St. Charles, MO
- St. Louis, MO
- Sunset Hills, MO
- Fenton, MO
- Kirkwood, MO
- Webster Groves, MO
- Ballwin, MO
- Chesterfield, MO
- Crestwood, MO
- Arnold, MO
- Manchester, MO
- Des Peres, MO
- Ellisville, MO
- Town and Country, MO
- Oakville, MO
- Affton, MO
- Clayton, MO
- Maryland Heights, MO
- Bridgeton, MO
- Florissant, MO
- University City, MO
If you have sinking or uneven concrete around your property, we can evaluate the issue and recommend the best solution.
We offer free estimates, and you can even send photos for a fast quote.
About Saint Louis Polyjack
Saint Louis Polyjack specializes in polyurethane concrete leveling, lifting, and structural repair throughout St. Louis, MO and surrounding communities. We raise and stabilize sinking driveways, sidewalks, patios, pool decks, warehouse floors, and more using advanced poly foam technology.
Our process is fast, clean, and long-lasting — backed by a 5-year warranty.
Office Location : 12951 Gravois Rd. Ste. 100 St. Louis, MO 63127
Uneven Concrete? Don’t Replace It — Lift It.
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✉️ stlpolyjack@stlpolyjack.com
Serving St. Charles, St. Louis, Sunset Hills, Fenton, Kirkwood, Webster Groves, Ballwin, Chesterfield, Crestwood & Arnold.
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