Sinkholes form under a driveway when the supportive gravel base wears away due to poor drainage of acidic water. Air pockets beneath the surface will eventually cause the concrete to sink. These holes start off small, but can expand quickly. Large sinkholes call for removing the entire driveway to fix the structural problem with the foundation. If the sinkhole is only in one section of the driveway, you can fix it over a weekend and stop the hole from spreading.
Drill small holes in the driveway surface. The holes must go through the entire slab and into the subbase below. Have a contractor pump concrete into the holes to slowly fill the sinkhole beneath the surface. The existing surface will lift until it is level with the rest of the driveway. The new concrete will provide a supportive base for the driveway so it doesn’t sink again.
Dig out a drainage channel parallel to the driveway with a shovel. Make it 10 inches wide and about 18 inches deep. Fill the bottom with a 6-inch layer of gravel and slope the gravel toward the street. Dig the channel away from the driveway to an area with adequate drainage.
Lay perforated PVC drain pipes down the length of the channel, cutting the pipes with a handheld rotary tool and cutting accessories if necessary for a proper fit. Cover the pipes with gravel and fill the top with the dirt and grass you removed to dig the channel. Installing drain pipes along the driveway will enable acidic water to drain away faster before it can damage the foundation again.
Fill any cracks or holes in the surface with vinyl patch compound to prevent water from seeping into the foundation. Use a putty knife or trowel to stuff the compound in the holes and smooth the top.
Seal the driveway with penetrating acrylic sealer and roller brush to repel water and fill the porous material.
Things You'll Need:
- PVC perforated drain pipe
- Handheld rotary tool
- Cutting accessory
- Vinyl patch compound
- Putty knife
- Roller brush
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