How to Repair Concrete Cracks
Fix cracks in driveways, sidewalks, and patios before they get worse
What You'll Need
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Tools
Wire brush
Hammer and cold chisel
For widening cracks
Caulk gun
For crack filler cartridges
Putty knife or trowel
Safety glasses
Materials
Step-by-Step Instructions
Clean out the crack
10-15 minutes
Use a wire brush to remove loose concrete, dirt, and debris from the crack. For stubborn material, use a hammer and cold chisel. Blow or vacuum out dust.
Pro Tip
A crack should be at least 1/4 inch wide and 1/2 inch deep for filler to adhere properly.
Widen the crack if needed
10-15 minutes
If the crack is less than 1/4 inch wide, use a cold chisel and hammer to widen it to 1/4 inch. This gives the filler more surface area to bond to. Clean again after chiseling.
Pro Tip
Make the bottom of the crack slightly wider than the top (dovetail shape) for better filler retention.
Warning
Wear safety glasses - concrete chips fly when chiseling.
Prepare deep cracks
5 minutes
For cracks deeper than 1/2 inch, insert backer rod first. Push it into the crack leaving about 1/4 inch depth for filler. This saves filler material and allows it to cure properly.
Apply crack filler (for narrow cracks)
10-15 minutes
For cracks 1/4 to 1/2 inch wide, use a caulk-style concrete crack filler. Cut the tip at a 45-degree angle. Fill the crack from bottom to top, slightly overfilling. Tool smooth with a putty knife.
Pro Tip
Work the filler in with your finger or a tool to eliminate air pockets.
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Track This Project FreeApply patching compound (for wide cracks)
15-20 minutes
For wider cracks or chips: mix concrete patching compound per directions. Work it into the crack with a putty knife or trowel. Smooth the surface level with the surrounding concrete.
Pro Tip
Misting the crack with water before patching helps adhesion.
Texture to match (optional)
5 minutes
While the patch is still workable, texture the surface to match the surrounding concrete. Use a broom for a brushed texture, or a sponge for a smoother finish.
Allow to cure
24-48 hours
Keep the patch moist for the first 24-48 hours for proper curing. Cover with plastic or mist periodically. Avoid foot traffic for 24 hours, vehicle traffic for 7 days.
Pro Tip
Curing is important - too fast drying causes weak, crumbly patches.
Common Mistakes to Avoid
- Not cleaning the crack thoroughly first
- Filling a crack that's too narrow (filler can't bond)
- Using the wrong product (mortar vs concrete patch)
- Not allowing proper cure time
- Filling over loose or crumbling concrete
Safety Warnings
- Wear safety glasses when chiseling concrete
- Wear gloves - concrete products are alkaline and irritate skin
When to Call a Professional
If the concrete is heaving (one side higher than the other), if there are large sections of damage, if cracks are very wide or growing rapidly, or if foundation walls are cracking.
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Frequently Asked Questions
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Project Overview
- Difficulty
- Beginner
- Time
- 30-60 minutes (plus cure time)
- Est. Cost
- $10–$40
- Tools
- 5 items
- Materials
- 3 items
- Steps
- 7
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