Concrete cracks
Why Concrete Cracks and Which Cracks Need Repair
Every slab cracks some. Here is how to tell a crack you can seal and watch from one that means the ground under it has moved.
Free, no-obligation estimates, and a straight answer about the crack.
- We look before anyone quotes a fix
- Same-working-day callback
- The whole job quoted before we start
Every slab moves
Why concrete cracks
Concrete cracks to some degree no matter how well it was poured, because temperature changes, settling and curing shrinkage all put stress on the slab.
A slab grows and shrinks a little with every hot afternoon and cool night, the ground under it settles, and fresh concrete shrinks as it cures and dries. Concrete does not stretch, so it lets go of that stress with a crack.
That is why a crack on its own is not a verdict on the slab. What matters is how wide it is, whether it is growing and what is behind it, and that is what we look at when you call.
The American Cement Association publishes research on how concrete behaves and why it cracks.
What is behind it
Common causes of cracks
Most cracks come from soil movement, heat and weather, heavy loads, water, tree roots, a poor installation or plain wear over the years.
Knowing which one cracked your slab tells you whether a fill will hold, or whether the cause has to be dealt with before the crack is.
Not sure which one it is? Describe the crack on the phone and we will tell you what we would look for.
Here is what cracks a slab, cause by cause:
- Soil movement
The ground under the slab settles or shifts, and the concrete follows it down.
- Weather and temperature extremes
Heat and cold swing the slab through expansion and contraction, day after day.
- Heavy loads
Vehicle traffic and weight a slab was never meant to carry bend it until it breaks.
- Water
Water that gets into concrete weakens it and opens cracks wider.
- Tree roots
Roots growing under a driveway or walk push the slab up from below.
- Poor installation
A slab poured on a poorly prepared base, or without well-placed joints, cracks sooner and in worse places.
- Normal wear
Years of sun, traffic and use take their toll on any slab.
Read the width
Reading crack width
A crack under a quarter inch wide can often be sealed and watched, while a crack wider than that points to movement in the sub-grade, the packed soil under the slab.
Under a quarter inch
Seal it and watch itAn isolated narrow crack with the slab level on both sides is usually the concrete relieving stress, not the ground giving way.
- Both sides sit at the same height
- The width holds steady from season to season
- Water runs off instead of pooling along it
The fix: clean it out, fill it with color-matched caulk or patching compound, and keep an eye on it.
Wider than a quarter inch
Look under the slabA crack this wide says the sub-grade has moved, so the cause sits below the surface and the repair starts with finding it.
- One side sits higher than the other, a trip edge
- The edges crumble or water pools along it
- The crack keeps getting wider
We come out, look at the crack and tell you plainly which side of the line it is on.
Small cracks, simple fix
Fixing small cracks
Hairline cracks and small chips are cleaned out and filled with color-matched caulk or patching compound, so the repair blends into the slab around it.
A small crack repair runs in four steps:
- Clean out the crack
Dirt, weeds and loose bits come out, so the filler bonds to sound concrete and not to grit.
- Fill it flush
The filler is packed in until it sits level with the surface, leaving no ridge to catch a foot or hold water.
- Blend it in
The fill is smoothed and textured to the slab around it, so it reads as part of the concrete instead of a stripe across it.
- Watch it
A sealed crack that holds its width is done. One that opens again is telling you the cause is still at work.
Minor cracks can be fixed by a contractor or by a capable homeowner. If you would rather it was done once and matched to the slab, or you are not sure the crack is minor, call us and we will look at it first. The American Concrete Institute publishes the trade's guidance on concrete repair.
When a patch is not enough
When cracks point to bigger problems
A crack that keeps growing, a crack pushed up by roots and a crack in the wrong place all point past a simple patch.
These are the cracks we would rather see in person, because the fix starts with whatever caused them, not with the filler.
Cracks from tree roots
Roots growing under a slab heave it up and crack it, and they are one of the usual causes of driveway cracks. Replace the slab and leave the roots, and the new concrete heaves the same way, so the roots come out first.
Cracks that need concrete repair
Left alone, small cracks grow as water gets in, temperatures swing and the ground moves. The edges can crumble into a trip hazard and a low spot where water pools.
Planned cracks at control joints
Control joints are the straight cut lines in a slab, planned weak points that make shrinkage cracks form at the joint instead of wandering across the slab. A crack that runs along one is usually doing its job.
Seeing one of these? We answer the phone or call back the same working day.
From our Google reviews
Neighbors on the work we do
These are our own Google reviews, shown exactly as they were written.
I hired this concrete contractor for my driveway replacement and I couldn’t be happier with the results. The team was professional, showed up on time, and worked efficiently to get everything done ahead of schedule. The finish is smooth, durable, and really improved the curb appeal of my home. I would definitely recommend them for any concrete work.
Nick, and coworker did a outstanding job. Working on our front yard. My neighbor was so impressed he’s planning on hiring Nick, to do their front yard. Thanks, Nick
Trustworthy, dependable, and quality service. Greenscape Projects transformed my backyard space into a beautiful oasis. Budget friendly prices. Affordable landscaping made possible with greenscape Projects. They arrived on time, cleaned up afterwards and sent pictures of the progress. Trust Greenscape Projects for all of your landscaping, gardening, yardscaping needs.
Not sure about your crack? We will come and look.
Tell us where the crack is and what it is doing. We look at the slab, tell you plainly whether it needs a fill, a fix underneath or nothing yet, and quote the whole job free before any work starts.
We show up when we say we will, and we clean up when the work is done.