Cracked or sunken concrete around Portland can often be lifted with cement grout or polyurethane foam, sealed, ground, patched or resurfaced. Replacement is better when slabs are badly broken. Because so many failures trace back to water, a lasting repair usually includes fixing downspouts and drainage. Moving hillsides or foundation cracks call for an engineer first.
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Not every cracked or sunken slab needs to come out. Depending on the cause, concrete can often be lifted, sealed, patched or resurfaced for less money and mess than replacement. In the Portland area, the cause is very often water, so the most useful repair conversations start with where the rain goes.
Why concrete cracks and sinks around Portland
- Saturated soil. Long wet seasons keep silty and clay soils damp, and saturated soil gives less support. Slabs over poorly drained ground settle unevenly.
- Washed-out edges. Downspouts that dump next to a walk or driveway, and runoff down sloped lots, carry soil out from under slab edges and leave voids.
- Loose backfill. Soil placed against foundations and along garages when the house was built often settles for years, which is why steps and patios pull away from the house.
- Tree roots. Street trees and big yard trees lift sidewalks and driveway edges throughout older Portland neighborhoods.
- Hillside movement. On steep ground in the West Hills and other slopes, slowly creeping soil can crack slabs and walls. DOGAMI rates the wind-blown silt on steep Tualatin Mountains slopes as highly susceptible to landslides.
- Freeze-thaw and deicers. Ice storms and occasional hard freezes, plus any salt, can scale concrete that isn't air-entrained or was finished poorly.
Repair options
- Slab lifting with cement grout (mudjacking): a cement-based slurry is pumped through drilled holes to raise a sunken slab and fill voids.
- Polyurethane foam lifting: expanding foam is injected through smaller holes. It's light and cures quickly.
- Crack and joint sealing: flexible sealant keeps rain out of cracks and joints so the base stays drier.
- Grinding: a small raised edge on a walk can sometimes be ground down to remove a trip hazard.
- Patching and resurfacing: repair mortars and thin overlays can renew a scaled but sound surface.
- Section replacement: badly broken panels are cut out at joints and repoured.
Fix the water too
Lifting a slab without fixing the drainage usually buys a few years. Extending downspouts, regrading, or adding a drain or a soakage feature keeps the base from washing out again. In the City of Portland, check with the Bureau of Environmental Services before disconnecting or rerouting downspouts or adding a drywell, since some setups need approval and lots differ.
City sidewalks
If the trip hazard is on the public sidewalk in Portland, the adjacent owner is responsible for repairs, and PBOT may send a Sidewalk Repair Notice. Repairs in the right-of-way need a permit and inspection, and the city lists vertical steps of one-half inch or more among common defects. Read our sidewalk repair notice guide before hiring.
When it might be structural or geotechnical
Cracks in a garage floor or patio are usually not structural. Cracks in foundation walls, doors and windows that suddenly stick, retaining walls that lean, or ground cracks on a slope after heavy rain are different. Those call for a structural or geotechnical engineer before any concrete work.
Questions to ask
- What do you think caused this, and how will the repair address it?
- Lift, patch or replace, and why?
- How will the holes or patches look afterward?
- Is there a warranty if the slab settles again, and what's your CCB license number?
Have a sunken slab or a trip hazard? Mark your request as urgent and request a concrete repair contractor.
See how it works
Frequently asked questions
Is mudjacking or foam lifting better?
Both can raise sunken slabs that are otherwise intact. Cement grout lifting is long established and heavier; polyurethane foam uses smaller holes, is lighter and cures quickly. The right choice depends on the slab, the voids and the contractor's experience.
Can a trip hazard on my Portland sidewalk be ground down?
Sometimes. Small vertical edges can be ground or a sunken panel lifted, but work in the public right-of-way needs a permit and must meet PBOT standards. Ask whether the fix will clear the defect cited on any notice.
Why does my concrete keep sinking after winter?
Often because water is washing soil out from under the edges or the base stays saturated. Extending downspouts, regrading and sealing joints help. Lifting a slab without fixing the water usually only lasts a few years.
Sources and further reading
- Oregon Construction Contractors Board: license requirements
- Oregon CCB: Guide to home improvement contracts
- Portland Bureau of Transportation: driveways
- Portland Bureau of Transportation: sidewalk repair notices
- Portland Permitting & Development: outside work permits
- Portland Bureau of Environmental Services: Clean River Rewards
- Portland Water Bureau
- City of Gresham Permit Services
- OSU Extension: clay soil challenges for Oregon gardeners
- DOGAMI: landslide hazard and risk study, Multnomah County (IMS-57)
- National Weather Service Portland
- Oregon 811: call before you dig
- American Concrete Institute (ACI)
- Portland Cement Association (PCA)