How To Fill Concrete Slab Voids
Voids under sidewalks, driveways, pool decks, and other structures can lead to cracks, voids, and uneven concrete. Usually, the soil beneath the foundation slab is to blame. However, as we explain below, there’s much more to it than that.
Below, you’ll discover how concrete lifting experts fill voids under slabs, helping create a safer living environment for you and your loved ones.
What Causes Concrete Slab Voids?
Concrete slab voids form for various reasons, including:
- Soil erosion: When too much water comes into contact with a concrete slab, soil erosion can occur, leading to voids. Drainage problems and leaky plumbing are two of the top causes of soil erosion.
- Soil settlement: Soil must be properly compacted before you place concrete on top of it. Otherwise, the soil can compress unevenly, resulting in slab voids.
- Freeze/thaw cycles: Sudden changes in temperature cause freeze-thaw cycles that increase soil erosion risk and slab void formation.
- Gutters and downspouts: Ineffective gutters and short downspouts may fail to direct water away from concrete slabs, contributing to soil erosion and voids.
- Drought: Expansive clay soil shrinks in dry weather, which often leads to voids.
- Hydrostatic pressure: When water under a concrete slab can’t drain, hydrostatic pressure might build up, causing the slab to crack and become uneven.
- Poor maintenance: If concrete slabs are not properly maintained, they can deteriorate over time, increasing the risk of concrete voids.
- Burrowing animals: Rabbits, squirrels, and other creatures can also cause void formation.
Filling Slab Voids: Polyurethane Foam vs. Mudjacking
There are two main ways concrete lifting experts like Groundworks fill voids under concrete slabs:
Polyurethane Foam Injection
This solution involves drilling holes into the concrete slab and injecting polyurethane foam beneath it. The foam lifts the slab, fills voids, and can potentially restore it to its original position.
Unlike mudjacking, polyurethane foam won’t shrink, erode, or settle. Plus, you can use your concrete slabs immediately after the repair is complete.
Mudjacking
This is an outdated concrete lifting method that some contractors still use today. It involves drilling larger holes in concrete and injecting a slurry mix of cement, sand, and water through the holes and into the slab.
Mudjacking is cheaper than polyurethane foam. However, it doesn’t expand as quickly to fill voids under concrete. That means you might still have voids after the repair. The mudjacking mix requires time to cure, which can take up to three weeks. This means you won’t be able to use your slabs immediately, unlike with polyurethane foam.
Alternative Slab Repair Methods
Alternative repair methods include full and partial slab replacement.
Partial Slab Replacement
Partial slab replacement involves removing one or more slab sections to access the voids. The voids are then filled with a concrete and sand mix before new slab sections are poured.
Full Slab Replacement
Full slab replacement is expensive and time-consuming, but it might be necessary if you have a lot of damage. Freshly poured concrete takes up to three weeks to cure, and you won’t be able to use the new slab during this time.
How to Avoid Concrete Slab Damage
After repairing or replacing a concrete slab, you can prevent future problems with proper drainage practices. For example, channel water away from the slab by cleaning gutters and installing longer downspouts. You can also regrade your yard or install a French drain to prevent water from pooling around the slab foundation.
Contact Groundworks for Expert Concrete Slab Solutions
Voids under concrete slabs don’t have to be a problem. Groundworks offers a range of custom-engineered concrete lifting solutions, including our PolyRenewal™ polyurethane foam injections, which offer same-day use.
Contact us today for a free inspection and to learn more about safeguarding your property.
Concrete Slab Lifting FAQs
Polyurethane injection is fast, non-invasive, and capable of supporting heavy loads, making it perfect for industrial and commercial needs.
It’s fast, strengthens the soil base, minimizes downtime, and eliminates the need for costly excavation.
It’s a no-excavation, fast-installation solution that levels floors efficiently and cost-effectively.
