You pull in. The headlights hit a crack running across the garage floor. Was it there last year? Probably. Is it bigger? Maybe.
Garage floors crack a lot. Most of those cracks are not a problem. Some are. This post is about telling them apart, with a focus on what makes a garage different from the rest of the house.
Five ways a garage floor is built differently
Same concrete. Different job. Here’s what’s different:
- It’s sloped on purpose. The California Residential Code, as adopted locally, says the parking area of a garage floor must slope so liquids move to a drain or toward the main vehicle door. A floor that slopes isn’t a sign of settlement by itself.
- It may have no vapor barrier. The code calls for a vapor retarder under concrete floor slabs, but it lists garages among the exceptions. Ground moisture can come up through a garage slab more freely.
- It carries point loads. Car tires, jacks, a loaded workbench, a gun safe, a second fridge. The house floor rarely sees that.
- It meets the house at a step. That step, or curb, is often the top of the foundation wall between garage and living space.
- It meets the driveway at the door. Two separate slabs, often poured at different times, meet under the garage door.
Keep those five in mind. They explain most of what you’ll see.
Why Poway ground adds to it
A lot of Poway sits on old sedimentary rock and the soils that weather from it. The California Geological Survey describes the Friars Formation, mapped across parts of the Poway area, as sandstone and claystone. Claystone weathers into clay that swells when wet and shrinks when dry. The City’s hazard plan annex tracks expansive soils as a hazard.
Many Poway homes also sit on graded pads. Part of a pad can be cut into native ground and part built up with fill. If the garage straddles that line, one end can settle differently from the other.
Common garage marks we shrug at
These are common and usually cosmetic:
- Hairline cracks that wander across the floor. Concrete shrinks as it cures. These show up early and stay thin.
- Cracks along the control joints. The saw-cut or tooled lines are there so the slab cracks along them. That’s the joint doing its job.
- Corner cracks at a column or re-entrant corner. Stress gathers at inside corners. A short, thin diagonal is typical.
- Surface flaking near the door. Water, sun and tire traffic wear the top layer. That’s a surface issue, not a structural one.
Red flags on a garage floor
These deserve attention:
- One side higher than the other. Run your hand across the crack. If you feel a lip, the slab has moved vertically.
- A crack that keeps getting wider. Measure it twice, a few months apart.
- Cracks that line up with cracks in the house wall on the other side of the garage step.
- A gap opening at the garage-to-house step. That can mean the slab and the foundation are moving apart.
- The garage door no longer seals at the floor, or one side of the door bottom shows daylight.
- Water or dampness coming up through the crack after rain or irrigation.
Do this first
Simple steps. No tools beyond a tape and a phone.
- Do sweep the floor and photograph each crack with a coin or ruler beside it.
- Do mark the ends of the crack with a pencil and write the date.
- Do check where the downspouts on that side of the house drain.
- Do look at the driveway joint at the door. Is water running back under the door?
- Do check the wall between garage and house. Look for new cracks or doors that stick.
- Do note heavy items and where they sit.
And skip this
- Don’t fill a moving crack with rigid patch and call it done. It’ll just crack again next to the patch.
- Don’t grind or cut a garage slab before you know whether it’s post-tensioned. Look for a stamp or tag near the garage door or in the plans.
- Don’t park a heavy trailer or RV on a slab edge that’s already cracked.
- Don’t seal the whole floor with an impermeable coating if moisture is coming up. You’ll trap it and the coating will peel.
- Don’t assume a sloped floor is a sinking floor. Slope toward the door is required.
The step between garage and house
This is the spot we look at hardest. The step is often part of the foundation that holds up the house wall. Cracks here can mean:
- The garage slab is settling away from the foundation. Usually a slab issue.
- The foundation itself is moving. A bigger issue.
Tell-tale signs of the second: cracks that run up into the drywall, a door between garage and house that binds, or cracks that continue into the house slab. If you see those, read our page on slab foundation repair.
What repair can look like
It depends on the cause. Common paths:
- Fix the water. Downspouts, grading and irrigation are first, every time.
- Seal and rout. For stable cracks, a flexible sealant keeps water and grit out.
- Structural crack repair. For cracks that need it, there are injection and stitching methods. Our foundation crack repair page explains the options.
- Slab replacement. For badly broken or heaved sections, sometimes replacing a panel is cleaner.
- Foundation work. If the house wall is moving, the fix goes below the slab.
When clay or fill is part of the story, coordinate with licensed engineers as needed. A soils look may be worth it on a pad that was graded. Our expansive soil page covers how that’s approached.
Permits
Some garage slab work is minor. Some isn’t. Replacing a section of slab or working on the foundation can need a permit. The City of Poway’s Building Services handles that. Ask before you start.
What shapes the cost
No prices here. Every garage is different. The cost moves with:
- How much of the slab is involved.
- Whether the house foundation is part of it.
- Whether the slab is post-tensioned.
- Access, and whether stuff has to be moved out.
- Whether a soils or engineering look is needed.
Wrap-up for Poway garages
Most garage cracks are shrinkage and joints. Watch for vertical offset, growth, water and anything that lines up with the house. Fix drainage first.
We cover all of Poway, from the older tracts near Poway Road to the hillside lots and large parcels. If something about your garage floor doesn’t sit right, request a Free Quote. Send a photo of the crack and one of the step. We’ll take it from there.