Uneven sidewalk sections are usually solid concrete that sank on one side of a joint, which creates a trip lip. We lift the low section back up to meet its neighbor with polyurethane foam, which removes the trip hazard without tearing anything out. A typical front walk takes an hour or two.
By Rob Diederich, owner · Updated
Typical job
2–5 sections
Time on site
1–2 hours
Walk on it
Right away
Warranty
Written warranty
The sunken section rises to meet its neighbor, so the trip lip and the puddle are gone. Drag the slider.
Trip hazards are a lift, not a replacement
Most uneven walks are a section that dropped at a joint. The concrete is fine; the soil under it washed out. Lifting brings the low side back up so the joint is flush again.
For businesses and HOAs, uneven walks are a liability issue. Under the 2010 ADA Standards, a change in level over 1/4 inch on an accessible route needs a bevel, and over 1/2 inch needs a ramp. Lifting removes the lip instead of working around it. See commercial concrete leveling.
Why sidewalk sections sink
Water washout
Roof and downspout water runs into open joints and carries fine soil out from under the slab. The slab drops into the hollow.
Fix: We seal the joints, and point out downspouts that need extending.
Freeze-thaw
Clay-heavy Green Bay soil holds water. Every winter it freezes, swells and thaws softer, loosening the base a little more each year.
Fix: Sealed joints keep water out of the base, which is what freezes.
Tree roots
Roots pull water out of the soil in dry summers, which shrinks it. If a root pushed the slab up instead, that's a grind-or-replace job, not a lift.
Fix: We'll tell you from the photos whether it sank or heaved.
Thin or loose base
Some slabs were poured on a thin or poorly compacted base. Gaps under the slab let it settle at joints and corners.
Fix: Foam fills the gaps and supports the slab across its whole footprint.
Lift or grind?
Grinding shaves a small lip down and can be the right answer for a slab that heaved up slightly. When a section has sunk, grinding the high side just leaves a low slab that holds water. Lifting fixes the cause.
How we fix a trip hazard, step by step
1Find the low side of each jointWe check every joint and mark which section dropped. The goal is flush: no lip at all, not just under the 1/4″ ADA limit.
2Drill 5/8″ holesPenny-sized holes go through the slab a few feet apart, kept off the edges and corners where concrete is weakest.
3Inject and lift to flushFoam fills the void, then lifts the low section in small steps until the joint is flush and the walk sheds water instead of holding a puddle.
4Patch and sealHoles are filled with cement grout and joints get a flexible sealant, so water can't wash the soil out again.
Illustrations, not to scale. Most residential jobs take a few hours, and you can walk on the slab when we pack up.
Why lift instead of replacing the section?
A replaced sidewalk section has to be barricaded while it cures, and new concrete next to old rarely matches. A lifted walk is open the moment we pack up, which matters for a storefront or an HOA entrance.
Fraction
of what tearing out and pouring new concrete costs
Same day
Walk on it when we pack up, not days later.
No demo
No jackhammers, no dumpster, no torn-up lawn or landscaping.
5/8″ holes
Penny-sized and patched flush. No new slab that won't match.
Stays up
Foam adds almost no weight and doesn't wash out like soil.
Warranty
Written, and spelled out in your quote before you approve it.
Replace
tear out + pour
Demo
Base
Pour
Keep off
Still curing: full strength in about 4 weeks
Lift
foam, one visit
Done in a few hours. Walk on it right away.
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Replacement timing is typical; a contractor's schedule and the weather can stretch it. New-concrete cure times from Concrete Network.
Your price, without a sales visit
Send three photos and a tape-measure shot. You'll get a firm price by text within 24 hours.
It can be. Uneven walks are one of the most common causes of trip-and-fall claims. For businesses, the ADA standards treat any change in level over 1/4 inch on an accessible route as something that needs to be addressed. Lifting the low section removes the hazard.
Who is responsible for fixing a public sidewalk in Green Bay?
Rules for sidewalks in the public right-of-way are set by each city, and responsibility can fall to the property owner. Check with your city's public works department; once it's approved, we can lift public sidewalk sections like any other.
Can you grind a trip edge instead of lifting the slab?
Grinding works for small lips on slabs that heaved up slightly. When a section sank, grinding the high side leaves the low slab holding water. Lifting fixes the cause and keeps the walk draining.
