Soil usually washes out from under a concrete driveway because water is flowing along or beneath the slab and carrying dirt away. Common sources include downspouts, runoff from higher ground, poor grading and gaps along the edges of the driveway.
This kind of erosion is easy to miss at first. You might notice a small gap under the edge, a hollow sound when you tap the concrete or soil collecting at the bottom of the driveway after storms.
Where the Water Comes From
Water doesn’t need to be dramatic to cause trouble. Over months and years, even moderate flows can move a lot of soil. Sources often include:
- downspouts that empty onto or beside the driveway,
- yards that slope toward the driveway,
- water running down a sloped driveway and off its edges, and
- gaps or open joints that let water reach the soil below.
Burlington and much of central North Carolina can see heavy downpours, especially in summer. Strong storms move a lot of water quickly, which makes erosion more likely where water collects or flows in one path.
Sometimes the water source is a neighbor’s yard or a street gutter rather than your own property. Noting where water enters during a storm can help pinpoint it.
Why Undermining Is a Problem
Concrete depends on the ground beneath it for support. When soil washes out, part of the slab may be left with a hollow space underneath. That area can crack, sink or break, especially when cars drive over it.
Washout near edges can also lead to crumbling, and voids under joints can cause one section to drop below another. These changes may happen slowly, then seem to appear all at once.
What Can Be Done
The first step is finding out where the water is coming from and how far the damage goes. Sometimes the fix starts outside the driveway, such as moving downspout outlets, improving grading or adding a way to carry water around the paved area.
If the concrete is still in good shape, filling voids or restoring soil along the edges may help, depending on the situation. If sections have cracked or sunk badly, they may need to be removed and replaced. Our article on replacing part of a concrete slab explains when partial replacement may work.
Don’t Wait Too Long
Erosion tends to get worse over time because each storm can remove more soil. Watching the area after heavy rain and taking photos can help a contractor understand the pattern.
Avoid digging under the slab yourself to check. That can remove more support and make the problem worse.
Our concrete driveway repair service looks at both the concrete and the water around it. If you’re seeing soil wash out under your Burlington driveway, get in touch and we’ll help you find the cause.
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