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Concrete · Lift before you replace

Driveway settling near the garage

Backfill against the foundation compacts over years and the slab follows it down. Mudjacking or foam lifting is usually cheaper than replacement if the slab itself is sound.

Quick answerThe soil dug out and refilled around a foundation when a house is built is looser than undisturbed ground. Over the years it compacts, and the end of the driveway resting on it sinks. If the slab is still in one sound piece, lifting it by mudjacking or foam injection is usually cheaper than tearing it out. Fix the water that’s softening the ground too, or it can sink again.

A drop at the garage apron is one of the most common concrete complaints. It’s also one where homeowners often get quoted for a full replacement when a lift would do.

A driveway leading to a garage, with autumn trees
A driveway running up to a garage. The section nearest the garage often sits on backfill, which is where settling shows first. Photo by Bruno Guerrero on Unsplash.

1Why the slab sinks there

  • Backfill compaction. The trench around the foundation is refilled after the walls go in. That fill settles slowly for years, and the driveway edge goes with it.
  • Water from the roof. Downspouts at the garage corners often dump water right where the slab meets the house, softening and washing out the soil.
  • Voids under the slab. Once a gap opens underneath, the slab is bridging air. It cracks or drops when a car rolls over it.

2How to check what you’re dealing with

  1. Look at the joint with the garage floorA step down from the garage slab to the driveway shows how far it has dropped. Note whether water now flows toward the garage.
  2. Look for cracks across the sunken partOne intact slab that has tilted is a lifting candidate. A slab broken into several pieces may need replacing.
  3. Find the downspoutsCheck where the garage downspouts discharge and whether soil at the slab edge is washed out.
  4. Tap and listenA hollow sound when you tap the slab can mean a void underneath.

3Fixing it

Do it yourself

  • Extend the downspouts so water lands well away from the slab
  • Regrade soil at the slab edges so it slopes away
  • Seal the joint between the garage floor and driveway
  • Mark and watch the drop through a season

Hire a pro

  • Lifting the slab by mudjacking or foam injection
  • Filling voids under the slab
  • Replacing sections that are broken or spalling
  • Water is now running toward the garage or house

Mudjacking pumps a cement-based slurry under the slab; foam lifting uses an expanding polyurethane. Both raise the slab and fill the void. Ask the contractor which they use, how many holes they’ll drill, and how they’ll patch them.

4What drives the cost

Lifting is priced mainly by how much slab is being raised and how much material it takes to fill the void underneath. Replacement adds breaking out, hauling away, base preparation and a new pour. Get both options priced if the contractor offers only one.

Concrete cost

Driveway dropping at the garage?

Talk to a concrete contractor who will tell you whether the slab can be lifted before quoting a replacement.

877-360-4657

5Questions

Will it keep sinking after it’s lifted?

It can if the soil keeps washing out. Redirect roof water and fix the grade at the edges so the ground under the slab stays drier.

When is replacement the better choice?

When the slab is broken into pieces, badly spalled, or so out of shape that lifting won’t give a usable surface.

Is this a foundation problem?

Usually not. It’s the fill next to the foundation compacting. If you also see cracks in the garage walls or sticking doors, have that looked at separately.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.

877-360-4657