Cracked, Sunken and Heaved Concrete:
Driveways, Walkways and Patios
Nearly every driveway Russ inspects has cracks. The ones he writes up as more than typical are the ones that trip people or send water toward the house.
A La Center driveway where tree roots had lifted the slabs so far out of line that someone had ground down the raised edges. A Portland patio with a void under its edge where the soil had washed out. A Vancouver driveway that had settled next to the house until it sloped back toward the foundation.
Concrete outside the house cracks. In Russ’s recent reports, 142 of 269 houses had a finding on a driveway, walkway or patio, and about two-thirds of those were written up as typical or minor cracking. The rest are the ones this post is about: offsets that trip people, slabs that sank, roots that heaved them, and surfaces that send water the wrong way.
Normal cracks and the ones worth more attention
Concrete shrinks as it cures and keeps moving a little with the soil and the seasons. That’s why driveways have control joints, the straight grooves cut every few feet, to give the cracks a planned place to go. Cracks still show up between them. Hairline and small cracks that stay flat are what Russ writes up as typical: worth sealing to keep water out, not a sign of anything wrong underneath.
The ones that get more attention have one of these:
- An offset. One side of the crack is higher than the other. That’s the trip edge.
- Width. Cracks wide enough to fit a coin, or that keep opening.
- Settlement. A section that has sunk below its neighbors.
- Heave. A section pushed up, usually by roots.
- Water. A slab that ponds water or slopes toward the house.
A Lake Oswego patio had a crack wide enough to expose its reinforcing mesh. A Vancouver driveway had old crack repairs whose sealant had itself cracked and failed. Patched cracks in a Portland driveway showed where earlier settling had been filled.
Trip hazards and the quarter inch
About a third of the flatwork findings in Russ’s reports included a trip hazard. His reports flag vertical offsets of more than 1/4 inch in walking surfaces. That’s about the edge height a toe catches without anyone noticing it, and it’s the same threshold accessibility guidelines use for a level change that needs no special edge treatment.
Offsets showed up everywhere: front walks in Beaverton and Vancouver, back patios in Portland and Gladstone, a patio-to-deck transition in Gresham, and paver walks in Lake Oswego, Portland and Brush Prairie where individual pavers had settled or come loose. One Battle Ground walkway had rebar sticking up out of it. An Aloha water meter vault lid sat below the sidewalk, and an Estacada sewer cleanout cover in the driveway didn’t sit flush.
Steps are their own category. A walkway that ends in a short step with an uneven riser is covered in the post on stairs that trip people.
Settling, voids and water
Settlement was the most common reason a slab got more than a “typical” note, in about 59 houses. Slabs sink when the soil under them was poorly compacted, washed out, or got soaked. Water is usually involved.
A Beaverton patio had evidence of undermining, where soil had washed out from beneath the slab’s edge. A Portland patio had voids and cracks under its edge from soil erosion. A Forest Grove patio was cracking and pulling away from the house. And in Vancouver, a driveway next to the house had settled enough to slope back toward the foundation, which sends rain right where it shouldn’t go.
That last one connects flatwork to the house. A patio or walk that tilts toward the foundation is a grading problem as much as a concrete one. Downspouts and drain lines that dump water at a slab edge are a frequent cause of the washout underneath, and the post on downspout drain lines and storm drains covers where that water is supposed to go.
Tree roots, asphalt and surface wear
Roots lift slabs. Russ found root damage to walkways in Lake Oswego and Beaverton, a La Center driveway where roots had heaved and displaced the slabs, and root upheaval in asphalt driveways in Portland. Cutting roots to fix the slab can hurt the tree, so an arborist is often part of the conversation. The post on trees near the house covers what roots do to foundations and sewer lines too.
Asphalt fails differently than concrete. It cracks in a pattern of small blocks called alligatoring, humps, and settles in soft spots. A Hillsboro asphalt driveway had deep longitudinal and alligator cracks that pointed to a weak base underneath. Portland and Oregon City asphalt driveways had cracking, humps and settling.
Surface wear on concrete looks like scaling, flaking or exposed aggregate. A Vancouver patio had scaling and an uneven finish with the aggregate showing. A West Linn driveway had large cracks and standing water, and the report noted the pooling would speed up the surface wear.
Real Inspection Photos
Driveway, Walkway and Patio Findings From Russ's Inspections
Root heave, voids, settling and cracks in outdoor concrete and asphalt from Russ's recent reports.
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Walkway slabs pushed up and out of line by tree roots, leaving uneven edges. -
Soil had eroded from under the edge of this patio slab, leaving a void and cracks. -
The driveway next to this house had settled enough to slope back toward the foundation. -
A patio crack wide enough to expose the reinforcing mesh. -
Deep longitudinal and alligator cracks in an asphalt driveway, pointing to a weak base underneath.
Who fixes what, and what the inspection covers
Russ walks the driveway, walks and patios, notes cracks, offsets, settlement, heave, surface wear and drainage, and measures offsets that look like trip edges. He notes where a slab slopes toward the house and looks for the cause when it’s visible. He can’t see under a slab. When something goes beyond typical, the report recommends a concrete contractor, and sometimes an arborist or a drainage contractor.
Common fixes, for context: sealing cracks to keep water out; grinding a small raised edge; lifting a sunken slab with grout (mudjacking) or polyurethane foam; or removing and replacing badly broken or root-heaved sections.
The public sidewalk is a separate question. In Portland, city code makes the adjacent property owner responsible for building and maintaining the sidewalk. If the city posts a repair notice and the owner doesn’t act, the city can hire the work out and bill the owner. Other cities have their own rules. The garage floor has its own post, garage floor slab cracks, since that slab is part of the house.
- Walk the front walk, driveway and back patio and look for edges you’d catch a toe on
- Look for sections that have sunk lower than their neighbors, especially next to the house
- Check whether any patio or walk slopes back toward the foundation
- Look for roots lifting slabs near trees
- Ask the sellers whether the city has ever posted a sidewalk repair notice
Cracks in outdoor concrete are normal; offsets, settlement, heave and slabs that slope toward the house are the ones Russ writes up as more than typical. About a third of the flatwork findings in his reports included a trip hazard. In Portland, the public sidewalk in front of the house is the owner’s to maintain.
The guide to what to look at outside the house before you make an offer covers grading, siding and the rest of the exterior. To set up an inspection, you can book online.
Driveway and Patio Concrete FAQ
