Is polyurethane concrete raising the same as replacement?

No. Polyurethane concrete raising lifts and supports existing concrete. Replacement removes the old concrete and installs new concrete.

How long does foam concrete raising take?

Many residential concrete raising projects can be completed in a single visit, depending on the number of slabs, site access, and project complexity.

Can cracked concrete be lifted?

Sometimes. Small, stable cracks may still allow the slab to be raised, but severely broken, crumbling, or structurally failed concrete may need replacement.

Will concrete raising fix water pooling?

It can improve pitch and drainage when settlement is part of the problem. Long-term results also depend on addressing the cause, such as downspouts, grading, or erosion.

Do I need to replace my whole sidewalk if one panel is uneven?

Usually not if the panels are still structurally intact. Targeted concrete lifting can often restore safer transitions with less disruption than replacing the entire walkway.

What measurement makes a sidewalk edge a concern?

The U.S. Access Board explains that changes in level above 1/4 inch generally require treatment, with beveled changes allowed up to 1/2 inch under specific slope limits.

What if the slab cannot be made perfectly level?

A trustworthy contractor should explain what is realistic before work begins. Final results depend on slab condition, surrounding concrete, obstacles, and how the slab responds during lifting.

Why Did My Garage Floor Sink?

Aug 8

Written By Tate Carlson

Your garage floor sank because the soil underneath it settled or washed away, leaving a void the slab could not span. Most garage floors are floating slabs poured over backfill that was placed during construction and never fully compacted. Water from downspouts, roof runoff, and poor grading speeds that settling up year after year. The concrete itself is usually still sound. The ground under it is not.

Key Takeaways

A garage floor slab rests on soil, not on footings, which is why the floor can drop several inches while the foundation walls stay exactly where they were.
Poorly compacted backfill along the foundation wall is the most common cause of a sunken garage floor in the Twin Cities.
Polyurethane foam lifting restores a garage slab to level in a few hours, and the garage is drivable the same day.
The foam weighs roughly 2 to 4 pounds per cubic foot, so it fills the void without adding weight to soil that already failed once.
Lifting the slab does not fix the water that caused the settling. If downspouts and grading are not corrected, the void will come back.
Lifting is not the right call for every slab. Concrete that has broken into several loose pieces or lost significant surface is usually better replaced than raised.

Your Garage Floor Sits on Backfill, Not on Footings

When your house was built, a trench was dug for the garage foundation, the walls went in, and the space inside was filled back with loose dirt. The garage slab was poured on top of that fill. Foundation walls sit on footings below the frost line, so they stay put. The slab has nothing under it but soil.

Backfill placed during construction is compacted, but not to the density of undisturbed ground. It keeps compressing for years afterward under the weight of vehicles, snow loads, and its own settling. That is why a garage floor can drop an inch or more while every wall around it stays level. It is also why the drop is almost always worst along the perimeter or near the garage door, where the fill is deepest and the water is heaviest.

Water Is the Reason the Soil Went Somewhere

Settling backfill explains slow, even sinking. Water explains the fast, uneven kind.

The usual sources we find:

A downspout discharging within a few feet of the garage wall instead of past the apron
Grading that slopes toward the garage rather than away from it
Roof runoff with no gutter above the garage door at all
A cracked or separated apron letting surface water run straight down the joint
Sump discharge lines that dump close to the foundation

Water moving through loose fill carries fine soil particles with it. Enough of that over enough seasons and you have an open void. The slab bridges the void until it cannot, then it cracks and drops.

Freeze and Thaw Cycles Widen the Void Every Winter

Minnesota ground goes through dozens of freeze and thaw cycles between November and April. Saturated soil expands when it freezes and shrinks back when it thaws, and it does not settle back into the same arrangement it started in. Each cycle leaves the fill a little looser and a little lower.

This is why a garage floor that seemed fine for fifteen years can drop noticeably over two or three winters. The void was building the whole time. The freeze and thaw cycles just finished the job.

How to Tell the Slab Settled and Did Not Just Crack

A settled slab and a cracked slab look similar from a standing position. These signs point to settling:

A visible gap between the slab and the foundation wall, sometimes wide enough to drop a pencil into
The bottom of the garage door no longer sealing evenly against the floor
Water running into the garage from the apron instead of out toward the driveway
A hollow sound when you tap the low area with a hammer or drop a wrench on it
Cracks that are wider at one end than the other, which means one side moved and the other did not
Storage shelves or a workbench sitting out of level against a wall that is still plumb

If you have the gap at the wall and the hollow sound, you have a void. That is a lifting problem, not a patching problem.

Polyurethane Foam Lifting Is the Repair, and It Is Not Mudjacking

Benchmark Concrete Raising lifts sunken garage floors with high-density polyurethane foam. We drill penny-sized holes through the slab, inject foam beneath it, and the foam expands to fill the void and raise the concrete back to level. The holes get patched, the foam cures in about fifteen minutes, and you can park on it the same day.

Mudjacking solves the same problem a different way, by pumping a sand and cement slurry under the slab. That slurry is heavy, often 100 pounds or more per cubic foot, and it goes on top of the exact soil that already proved it could not carry a load. It also requires holes closer to two inches across and a longer cure before the slab can take traffic.

Foam is the better fit for garage floors specifically because it is light, it expands into the smaller channels the water carved out, and it does not need the garage out of service for days.

What to Do Before You Call Anyone

Walk the outside of the garage and find every place water lands. Extend downspouts at least six feet past the wall.
Check the grade against the foundation. You want the ground dropping roughly six inches over the first ten feet.
Look at the apron in front of the garage door. If it has settled too, the joint is likely feeding water underneath both slabs. Here is how apron settling works.
Photograph the gap at the wall and measure it. That number tells a contractor how much lift the slab needs.
Fix the water source first or at the same time as the lift. A repaired slab over an uncorrected downspout is a temporary repair.

Get the Slab Looked At

Benchmark Concrete Raising lifts sunken garage floors, aprons, sidewalks, and steps for homeowners across [Blaine, Coon Rapids, Maple Grove, Plymouth, Eden Prairie, Woodbury, and the surrounding Twin Cities metro]. Estimates are free, and most garage floors are lifted in a single visit.

Request a free estimate or call 952-295-0500.

Frequently Asked Questions

Can a sunken garage floor be raised, or does it have to be replaced?

Most sunken garage floors can be raised. Polyurethane foam lifting works as long as the slab is still in reasonably solid pieces. Replacement makes more sense when the concrete has broken into several loose sections or the surface has badly deteriorated.

How long does it take to lift a garage floor?

Most garage floor lifts take two to four hours from setup to cleanup. The foam cures in about fifteen minutes, so you can drive on the slab the same day.

Will my garage floor sink again after it is lifted?

The foam does not compress or wash out, so the fill it replaces will not settle again. New settling can happen in an untreated area nearby if the water source that caused the first void is still active, which is why correcting downspouts and grading matters.

Is a sunken garage floor a foundation problem?

Usually not. Garage slabs float on soil while foundation walls sit on footings below the frost line, so a sinking floor next to level, plumb walls points to soil settlement rather than foundation movement. Walls that are cracked, bowed, or out of plumb are a different issue and should be evaluated by a structural engineer.

Tate Carlson