Control joints
How Concrete Control Joints Keep Cracks in Line
The straight grooves in your driveway are there on purpose. Here is what they do, how far apart they belong and why we seal them.
Free, no-obligation estimates. We answer the phone or call back the same working day.
- Free, no-obligation estimates
- Same-working-day callback
- The whole job quoted before we start
The grooves are the point
What a control joint does
A control joint is a planned cut that makes shrinkage cracks form at the joint, in a straight line, instead of randomly across the slab.
Concrete shrinks as it cures and dries, and that stress has to go somewhere. The joint is a weak line put in on purpose, saw cut or tooled into the fresh concrete, so the crack opens at the bottom of the groove where you never see it.
- "Control joint"
- The trade's word for what most people call the cut lines or the grooves in the concrete. People often call them expansion joints too; on a driveway or walk, the straight cuts are control joints.
So a crack that runs along a joint line is the joint doing its job. A crack that crosses the open slab is the one worth a look.
Spacing by the slab
Control joint spacing
On "flatwork" such as a driveway or patio slab, control joints go every 8 to 10 feet; on a 4-foot-wide sidewalk, they go every 4 to 6 feet.
Good installers space them as planned weak points that relieve the stress before it finds its own way out:
-
Driveways, patios and slabs
8 to 10 ft
between joints, cut as planned weak points that relieve the stress across a wide slab.
-
Sidewalks and front walks
4 to 6 ft
between cross joints on a walk of standard width, which keeps each panel close to square.
The American Concrete Institute publishes the standards and guidance contractors follow on concrete joints, placement and repair.
When the cut is skipped
Joints cut too late or missing
Leave the joints out, or cut them too late, and the slab cracks at random across its face.
On an older slab, a spread of random cracks often tells us the joints were too few or too far apart from the start.
Sealed, not left open
Sealing control joints
We fill control joints with a flexible joint sealer, which lets the slab expand and contract and keeps water and insects out of the voids below.
What makes the sealer right for the job:
- Flexible, not hard
A rigid filler cracks loose the first time the slab moves; a flexible sealer gives with it and stays in the joint.
- Kept full
Where old sealer has pulled away or gone missing, the joint is open again, and that is the gap we clean out and reseal.
Joints open, weedy or never cut?Call and tell us what the slab is doing. We look at the joints and the cracks before anyone quotes a fix.
(951) 439-3217Joints and repair work
Joints and repairs
Joints set the lines a repair is cut to, and the gaps that need cleaning out while we are there.
We work to the joint pattern your slab already has, so the repaired part lines up with the rest of it.
We answer the phone or call back the same working day.
Cutting out a sidewalk section to the joints
For larger repairs, the cleanest result comes from cutting the damaged section out to the nearest control joints and pouring it new.
The new panel then meets the old concrete along a straight joint line instead of a ragged patch edge, and the joint goes on doing its job.
Debris-packed joints and street creep
When joints pack with dirt and debris, slabs that expand can push against each other with nowhere left to go. The trade calls it "street creep", and it can shove a driveway into the garage or a walk into the house.
Cleaning the joints out and sealing them gives the slabs back their room.
From our Google reviews
Neighbors who called us
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.
Cracks wandering past the joints? We will come and look.
Tell us what the slab is doing. We look at the joints and the cracks, tell you plainly whether it needs sealing, a section cut out 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.