Is concrete leveling worth it?

A sidewalk section that has dropped at the front steps, or a patio that now tilts toward the house, makes most homeowners wonder whether to lift it or tear it out. Lifting is usually the better choice, but not always. Here is how to tell the difference on your own property in Sandy Springs.

The short answer

For most sunken slabs, leveling is worth it. If a sidewalk, patio, driveway section or porch step has dropped but the concrete itself is still sound, lifting it back into place is usually the sensible choice. You keep the slab you already paid for. The work is usually quicker and less disruptive than breaking out concrete, hauling it away and pouring new.

It stops being worth it in two situations. The first is when the slab is badly broken or crumbling at the surface. The second is when it is sinking because of a problem that leveling does not fix. If you lift a slab that sits over a washout from a leaking downspout, you only buy time until the soil moves again. So it is worth it when the concrete is sound and the cause can be dealt with. If either of those is missing, it is not.

What changes the answer on a real property

Three things decide it: the condition of the slab, the reason it sank, and what the slab does.

Start with condition. A slab with one or two clean cracks can be lifted and the cracks sealed. A slab broken into many pieces, or one with a flaking, pitted surface, will still look and wear like old concrete after it is level. At that point replacement is often the better use of your money.

The cause matters more than most people expect. Around Sandy Springs the soil under most homes is dense red clay. It swells when it is wet, shrinks in dry spells and washes out where water keeps running over the same spot. Summer thunderstorms drop a lot of water fast. On the sloped lots common across the area, that water finds the edge of a walkway or patio and works its way underneath. If a downspout empties right beside a slab, or the yard drains toward it, the soil will keep moving after the slab is lifted. Leveling lasts when the water problem is fixed first.

Large trees play a part too. Many older neighborhoods here have mature oaks and maples close to driveways and walks. Their roots can push up one side of a slab while they dry out the clay under the other side.

Then think about what the slab does. A sunken section of sidewalk at the front steps is a trip hazard and worth fixing soon. A patio that tilts toward the house sends rainwater at the foundation. A garage apron that has dropped a little may only be an annoyance. The more a slab affects safety or drainage, the easier the decision.

What you can check yourself

Before anyone comes out, a few minutes with a tape measure and a garden hose will tell you a lot.

Look at the joint where the sunken slab meets the next one. Measure the drop. Anything you could catch a toe on should be fixed. Next, run a hose onto the slab and watch where the water goes. Water that pools in the middle or runs toward the house tells you the slab is tilted the wrong way.

Walk along the edges. Gaps under the edge, or soil that has washed away from the side, point to erosion underneath. Follow each downspout and note where it empties and whether that water heads toward the slab. Check for large trees within a few feet. Finally, tap the surface with a hammer handle. A hollow sound over part of the slab suggests there is a void below.

Take a few photos while you do this. They make it much easier to describe the problem when you call.

When it needs a professional

Leveling itself is not a do-it-yourself job. It means drilling holes in the slab, pumping material under pressure and judging how much lift each section can take. Push too hard in one spot and you can crack a slab that was otherwise fine.

Call sooner rather than later in three cases: the slab sits against the house and has started to tilt toward it, the sunken area gets worse from one season to the next, or the settling is next to a retaining wall. On a hillside lot, a walkway or patio that drops along its downhill edge can mean the wall holding that soil is leaning or losing fill behind it. Then the wall needs attention before the slab, because concrete lifted on top of moving soil will not stay put.

How leveling fits with mudjacking and wall work

Concrete Leveling is the general term for raising a sunken slab back to its original height. Mudjacking is one way to do it. A cement-based slurry is pumped through small holes drilled in the slab. It fills the void underneath and pushes the concrete back up. It works well on sidewalks, patios, steps and driveway sections, and the material gives solid support where the soil has washed out.

We also build and repair retaining walls, so we look at the slab as part of the whole yard. A lot of the settling we see in Sandy Springs comes from soil moving on a slope. Sometimes the right order is Retaining Wall Repair first and leveling second. If a walkway is cracked and broken rather than just sunken, Sidewalk Repair may be the better fit. We will tell you which one we think the problem calls for.

What a visit involves

When we come out, we look at the slab, measure how far it has dropped, check the edges for washout and see where the water goes. We also look at any nearby walls or slopes that might be part of the problem. Then we explain what we think caused the settling, whether leveling makes sense and what else should be done so the slab stays level. If replacement is the better call, we will say so. You get an estimate before any work starts.