Concrete Void Filling

What Is Void Filling?

Beneath every concrete slab sits a layer of soil that provides structural support. Over time, that soil can erode, wash away, compact, or shift — leaving hollow spaces called voids. When your concrete sits over an unsupported void, it's only a matter of time before it cracks, settles, or collapses under weight.

Void filling is the process of injecting expanding polyurethane foam into these empty spaces beneath your concrete. The foam begins as a liquid, flowing into every gap and crevice, then expands to fill the void completely. In seconds, it cures into a dense, waterproof mass that permanently restores support to your slab.

Signs You May Have Voids Under Your Concrete

Not all voids are visible from the surface, but there are telltale signs to watch for:

• Hollow sounds — Tap or walk on your concrete. If sections sound hollow compared to others, there's likely a void underneath.
• Visible settling — One area of your slab is lower than adjacent sections, often creating a lip or step.
• New crack patterns — Cracks appearing where there weren't any before, especially in radiating patterns.
• Water pooling — Water collecting in areas where it didn't before indicates the slab has shifted.
• Bouncy concrete — If a section of your driveway or garage floor flexes when you drive or walk over it, there's a void below.
• Gaps at edges — Visible gaps between the slab edge and the adjacent structure (foundation, garage wall, etc.).

Why Voids Are Dangerous

Voids aren't just a nuisance — they're a structural problem that gets worse over time. Unsupported concrete is vulnerable to:

• Cracking under load — Vehicle weight, foot traffic, or heavy equipment can crack unsupported slabs.
• Water infiltration — Voids create channels for water to flow beneath your concrete, accelerating erosion and expanding the void.
• Foundation damage — Voids near your home's foundation can undermine structural support and lead to costly repairs.
• Sudden collapse — In severe cases, large voids can cause concrete to collapse unexpectedly — a serious safety hazard.

How We Fill Voids

Our void filling process is fast, minimally invasive, and permanent:

1. Assessment — We evaluate your concrete to identify void locations and extent. In some cases, we can feel where voids are by the sound and flex of the slab.
2. Drill access points — Small 3/8" holes are drilled through the slab at strategic locations.
3. Inject foam — Expanding polyurethane foam is injected through the holes. Because it starts as a liquid, it flows into every void space before expanding to fill them completely.
4. Cure and close — The foam cures in minutes. Holes are patched, and your concrete is usable within 2 hours.

Why Polyurethane Foam Is Ideal for Void Filling

Unlike grout or mudjacking slurry, polyurethane foam has unique properties that make it the superior choice for void filling:

• Flows before it expands — Reaches every corner of the void, even irregular shapes
• Lightweight — At ~2 lbs per cubic foot, it won't add significant weight to already-stressed soil
• Waterproof — Immune to water damage and freeze-thaw cycles
• Dimensionally stable — Won't shrink, compress, or erode over time
• Eco-friendly — Made from 39-49% renewable and recycled materials, certified toxic-free

Common Void Filling Applications

• Garage floors — One of the most common applications. Garage slabs frequently develop voids from soil settling and poor original compaction.
• Driveways — Heavy vehicle traffic accelerates void formation. Filling voids prevents cracks and collapse.
• Pool decks — Water runoff around pools erodes soil rapidly. Void filling prevents deck sections from settling unevenly.
• Commercial floors — Warehouse floors, loading docks, and retail spaces subject to heavy loads benefit from proactive void filling.
• Near foundations — Voids adjacent to foundations can compromise structural integrity. Filling them early prevents expensive foundation repairs.