Concrete leveling questions, answered

Concrete leveling raises a settled slab back to its original grade by filling the void under it with material injected through small holes. The slab you already have stays in place. It's an alternative to breaking out sound concrete and pouring new.

The slab follows the soil under it. Common causes are fill that was never compacted well (especially backfill next to a foundation), water from downspouts or sprinklers softening or washing out soil, plumbing leaks, freeze-thaw, and clay soils that shrink as they dry. Along the Front Range, expansive clay is common enough that we consider it on every job.

No. Leveling works when the slab is in one piece or a few large pieces and the cause of settlement can be controlled. Concrete broken into many small fragments, slabs pushed up by tree roots, and settlement tied to a foundation problem need replacement, root work or a structural engineer.

It's an alternative when the existing slab is still sound. If the concrete itself is failing (crumbling surface, heavy spalling, many broken pieces), replacement is the right call and we'll tell you so.

Foam leveling injects a two-part polyurethane through ports about 5/8 in wide; it expands, fills the void and lifts the slab, and it is very light. Mudjacking pumps a cement-based slurry through larger holes, roughly 1 to 2 in; it is much heavier and needs longer to cure. The process page compares them side by side.

Both. Soft or wet soil, slabs that need to carry traffic soon, and places where weight matters usually point to foam. Some large, dry voids are a reasonable fit for slurry. We explain which one we'd use on your slab and why.

During injection the crew follows the manufacturer's safety requirements and wears the protective equipment it specifies. The foam goes under the slab, not onto the surface around it, and once it cures it is a solid that stays in place.

Foam doesn't wash out. Slurry can be affected if water keeps running under the slab, which is one more reason the drainage problem behind the settlement has to be fixed either way.

Send the estimate form with the address, the slab that moved and a couple of photos. We follow up to arrange a visit to measure the slab, then explain the method and give you an estimate.

Move vehicles, planters and furniture off the slabs, make sure we can reach the work area, and let us know about sprinkler lines, invisible pet fences or other buried lines near the slab.

Many residential jobs take part of a day on site. Large commercial areas and groups of connected slabs take longer. We give you a time estimate after measuring.

It depends on the method and conditions. Foam can be placed in colder weather than cement-based slurry, but frozen ground, snow and ice on the slab, and very low temperatures can all push a job to a better day. We'll tell you if your job should wait.

Foam-lifted slabs can usually take foot traffic the same day. Slurry needs more curing time before vehicles. We give you the wait for your specific job before we leave.

A lift lasts as long as the soil and water conditions under the slab stay stable. That's why we point out downspouts, grading and irrigation problems: they are the most common reason a slab settles again.

They're patched flush with a cement-based patch. Patches can be visible up close because new material rarely matches weathered concrete, but foam ports in particular are small.

Yes, in most cases. Sealing control joints and cracks with a flexible sealant keeps surface water from reaching the soil under the slab. See joint and crack sealing.

There isn't one universal number for every setting, but the 2010 ADA Standards are a useful reference for accessible routes: vertical changes in level up to 1/4 in are allowed, 1/4 to 1/2 in must be beveled, and anything over 1/2 in needs a ramp. Many property managers use similar thresholds when they survey walkways.

Yes. Commercial and HOA work usually means walking the property, measuring and mapping the offsets, and scheduling the lifts around residents, tenants and customers. See commercial concrete leveling.

That depends on the city. Rules differ across Front Range municipalities and change over time, so check with your city's public works department before scheduling work on a public sidewalk.