Lift or Replace Sunken Concrete in Troy, MI?

Level sunken concrete in Troy, MI when the slab has settled in one piece, the surface is sound and the cause of settling can be fixed. Replace it when the slab is broken into several pieces, scaled across much of the surface or sitting on a washed-out base. Leveling with mudjacking or polyurethane foam costs much less than replacement, but it only works on slabs worth saving. Troy's sidewalk program follows the same logic: sunken flags can be leveled, but cracked or spalled flags must be replaced.

How concrete leveling works

Both common methods raise a slab by pumping material underneath it.

• Mudjacking (slabjacking): Crews drill holes about an inch or more in diameter and pump a cement-based slurry under the slab. As the void fills, the slab rises. It is a proven method and typically less expensive.
• Polyurethane foam lifting: Crews drill smaller holes and inject expanding foam. It is lightweight, cures quickly and adds little load to weak soils. It usually costs more per job.

Afterward, the holes are patched and joints should be sealed to keep water out.

When leveling makes sense

• The slab dropped evenly or tipped but stayed in one piece.
• The surface is in good condition, without widespread scaling.
• The cause, such as a downspout or poor grading, can be corrected.
• The slab has useful life left.

Common candidates: a driveway panel that sank near the garage, a sidewalk flag that created a trip hazard, a patio that tipped toward the house, or a garage floor section that settled.

When replacement is the right call

• The slab is broken into multiple moving pieces.
• Scaling or spalling covers much of the surface.
• The base washed out under a large area.
• The concrete was too thin for its use.
• The city requires replacement, such as cracked or spalled public sidewalk flags in Troy.

Lifting a broken slab just raises the pieces, which will crack and move again. Lifting a scaled slab leaves you with a level surface that keeps flaking.

Fix the water first

Most settling is caused by water. A downspout that discharges beside a slab, a gutter that overflows, or a yard that slopes toward the concrete can wash out the base. Before leveling, redirect downspouts, fix grading and seal joints. Otherwise, the slab may sink again.

Cost comparison

Leveling usually costs a fraction of replacement for the same area, because there is no tear-out, haul-away, base work or new concrete. That is why it is worth asking whether your slab is a candidate. Replacement brings a fresh, air-entrained surface and a corrected base, so it is the better value when the slab is near the end of its life. For a sense of what drives replacement cost, see our driveway cost guide.

Public sidewalks in Troy

If your sidewalk notice lists sunken flags that are intact, leveling may be allowed. If the flags are cracked or spalled, the city requires replacement. Both require following the city's process. Read our Troy sidewalk and approach permit guide and the Troy sidewalk program page for details.

Around Troy

In older neighborhoods near Troy Historic Village, tree roots and decades of settling create many trip hazards. Some flags are good candidates for lifting; others are too broken. Newer subdivisions see more settling at garage aprons where fill was placed during construction.

For help deciding, see concrete repair and leveling. If replacement is the answer for walks, see sidewalks and walkways.