Free, no email required

The Sunken Slab Checklist

Ten minutes, a tape measure and a level. Work through this before you call anybody, including us, and you will know whether you are looking at a lift, a replacement, or something that is not really about the concrete at all.

To check a settled slab yourself: measure the drop at the worst joint, tap the slab and listen for a hollow sound indicating a void, trace where water reaches it, confirm the slab is not cracked through, and check the house itself for sticking doors or stair-step cracking.

1. Measure the drop at the worst joint

Lay a straightedge or a level across the joint where two slabs meet and measure the gap under it at the low side. Write the number down. This single measurement decides more than anything else you will do today.

Under 1/4 inch: cosmetic, and usually not worth paying anyone for yet.
1/4 inch to about 2 inches: the normal range for lifting, and the cheapest point to deal with it.
Beyond roughly 3 to 4 inches: still often liftable, but ask directly whether replacement makes more sense.

2. Tap the slab and listen

Walk the slab and rap it with a hammer handle or the heel of your shoe every few feet. Solid concrete on soil sounds dull. A hollow, drummy note means there is an empty space underneath.

Mark where it sounds hollow. The void is almost always bigger than the visible dip.
A hollow slab that has not yet dropped is the cheapest possible time to fix this.
If the whole slab sounds hollow, say so when you call. It changes the material estimate.

3. Work out where the water goes

Stand at the slab and find every source of water that reaches it. This is the step people skip, and it is the reason some slabs get lifted twice.

Downspouts discharging within a few feet of the slab.
A grade that runs toward the slab or toward the house rather than away.
Irrigation or a hose bib near the low corner.
Any sunken area that holds water for a day or more after rain.

4. Check whether the slab is intact

Lifting works by floating a slab as one piece. A slab already broken into several pieces does not float, it just spreads.

Hairline surface cracks: normal shrinkage, not a problem for lifting.
A crack running fully through the slab, with the two sides at different heights: that panel may need replacing rather than lifting.
Crumbling, flaking or exposed aggregate across the surface: the concrete itself is failing, and lifting it does not address that.

5. Now look at the house, not the slab

This is the step that matters most and takes the least time. A house here sits on footings 42 inches down, below the frost line. Flatwork does not. They are supposed to move independently.

Open and close the doors on that side of the house. Sticking or out of square is a signal.
Look for stair-step cracking in brick or in a foundation wall, rather than cracking in the slab.
In the basement, look for a horizontal crack or any bowing in a poured wall.
If any of those show up, you want a foundation contractor first. Lifting the slab would hide the signal.

6. Photograph it properly

Three photos get you a far more accurate quote than a paragraph of description, and they save a visit.

One wide shot showing the whole slab and what it connects to.
One low shot along the surface, camera near ground level, so the dip is actually visible.
One close-up of the worst joint with a tape measure held in the gap.

Reading your own results

What Your Answers Mean

Hollow sound, small drop, intact slab. This is the ideal case and the cheapest one. There is a void, the concrete is still sound, and filling it now costs a fraction of what it will after the slab drops properly.

Big drop, intact slab, water source found. Straightforward lift, but the water has to be dealt with as part of the job or you will be reading this page again in three years.

Slab cracked through and tilted. Ask about replacing that panel specifically rather than the whole run. One bad panel in an otherwise good driveway is a panel-sized job.

Doors sticking, stair-step cracking in the wall. Stop and call a foundation contractor before anyone lifts anything. The slab is the symptom here, and lifting it removes the evidence without fixing the cause.

Which Slab Is It?

Each of these settles for a different reason, and the pages explain what is specific to that slab:

Background on why any of it moves in the first place is on why concrete sinks in Rockford. General guidance for homeowners, not an engineering assessment of a specific property.

Worked through it and want a number?

Send the three photos and the measurement from step one. That is enough for a fixed quote without a visit in most cases.

Get a Quote See Pricing