Why is my concrete driveway cracking or sinking?

All concrete shrinks slightly as it cures, and control joints are cut into the slab so that shrinkage cracks happen in straight lines where you expect them. Thin hairline cracks along or near those joints, with both sides level, are normal and mostly cosmetic.

Cracks that run diagonally across panels, cracks you can fit a coin into, and cracks where one side sits higher than the other are a different story. Those usually mean the slab has lost support underneath or is carrying more weight than it was built for.

A sinking panel almost always sits over a void or soft spot. Common causes are a base that was not compacted when the drive was built, downspouts or runoff that wash material out from under the edges, a slope that sends water under the slab, and fill soil that keeps settling for years after construction.

On Upper Cumberland lots, water is the usual culprit. Heavy rain and repeated freeze and thaw work into any gap at the edges and joints, and each cycle carries a little more of the base away.

• Poorly compacted or thin base
• Downspouts and runoff draining under the slab
• Settling fill soil on new construction lots
• Heavy trucks, trailers or equipment on a thin slab
• Missing or shallow control joints
• Tree roots lifting or cracking panels

Slab lifting, often called mudjacking or foam jacking, pumps material under a sunken panel to raise it. It can work on a panel that is still in one piece and only slightly low. It does not fix a panel that is badly broken, and it does not correct the drainage that caused the problem.

Whether lifting or replacement fits depends on how the panel broke and why the ground under it moved. Joe looks at both on the site walk and tells you which approach makes sense before anything is priced.

Replacement makes sense when several panels are broken, the slab has sunk in more than one place, the surface is crumbling, or the base under it has failed. A partial replacement, where the crew cuts out the bad panels and rebuilds the base beneath them, can work when the damage is limited to one area.

Replacing the slab is also the chance to fix what broke it: compact a proper base, correct the slope, move downspout water away and set the thickness for the vehicles you actually own.

Send a few photos of the cracks and any sunken areas through the request form at /request-estimate, or call the office. Joe walks the drive, checks the drainage and the base where he can see it, and gives you a written estimate for the repair or replacement that fits.