Voids underneath concrete are a common problem that many homeowners face.
If you notice that your concrete is developing empty spaces underneath it, you may be worried about what that means for the life of your concrete.
While concrete voids are a big problem that needs to be addressed, they’re also very common. As long as you have the right information, a good maintenance plan, and a good concrete repair team, the voids under your concrete likely won’t pose a big threat.
Key Takeaways
Voids under concrete slabs form when the material beneath settles, but the slab itself is rebarred into a nearby structure. If ignored, voids can cause damage to the adjoining structure and the slab itself. Concrete leveling can fill the void and support the slab, preventing further damage.
In This Article
What Are Voids Under Concrete?
We use the term “voids” to describe the empty spaces that can form underneath concrete slabs. These empty spaces, or voids, are usually places where the sub-material that the concrete was sitting on settles or erodes away.
How Voids Under Concrete Form
The voids can occur because the slab is supported by something other than the sub-material it’s sitting on (e.g., another slab or a wall), which allows it to stay supported as what’s underneath it settles away.
Voids are most common when concrete has rebar in it and/or it is rebarred into a retaining wall or the footer of a house.
Why Voids Under Concrete Are Bad
While it can seem like the concrete will be fine because it isn’t initially sinking or falling with the settling sub-material, if you do nothing to fix the issue, there’s a large risk of it collapsing or causing damage to what is holding it in place.
Waiting to address voids under your concrete can cause more damage in the long run.
Issues Caused by Voids Under Concrete
When the sub-material under concrete slabs settles in normal circumstances, the slabs settle with it. But because voids typically open up under slabs that are being supported by the walls of a house or connecting slabs, it can cause many problems:
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The slabs can pull on adjoining walls or house foundations, causing potentially severe damage to door frames, masonry, and walls.
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The slabs can pull down the slabs connecting to it, collapsing in on themselves.
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The unsupported section of concrete is a weak spot with a higher risk of cracking.
Pro Tip: Voids can cause more damage if it’s ignored. The problem doesn’t go away, but rather increases the stress on the surrounding support structures over time.
Example: Void Under Front Step
This is an example of damage that can happen as a result of waiting to repair concrete voids. The concrete had a void underneath and started to settle.
When it started to settle on the right-hand side, the left-hand side started to raise, like a teeter-totter. Because of this, it put pressure on the door frame, causing the door to stick and the wooden trim to be skewed, which resulted in additional repairs.
Example: Large Void Under Front Porch
These pictures show how rebar has this porch pinned to the house, while the soil underneath of it has settled. This could have been caused by the downspout not being extended properly or natural settling, or a combination of the two.
Example: Boarded-Up Void Under Steps
These photos show steps that developed a void underneath. The customer used a board to keep critters out, but didn't fill the void. Over time, the steps settled and started to pull on the walls of the porch because they were rebarred into place.
How To Fill Voids Under Concrete
While there is no complete solution for avoiding naturally occurring empty spaces under concrete, you can prevent worse outcomes if you stabilize the area before bad damage happens.
Concrete leveling is a great way to do this, as it fills the voids with a strong compound that provides a new base to support the concrete so it no longer has to pull on surrounding structures.
Fill the Voids Under Your Concrete Slabs
Voids under concrete slabs can be a big problem if not taken care of properly, but addressing the situation before damage occurs is the best possible plan of action.
A-1 Concrete Leveling has been specializing in concrete leveling and stabilizing concrete voids for over thirty years. Request a free estimate today!
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