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Caulking Concrete Cracks

Seal cracks in concrete with durable urethane caulk. It'll keep water out and protect your foundation and walks from further cracking and eroding. You can do it in less than a half hour.

By the DIY experts of The Family Handyman Magazine

Caulking Concrete Cracks

Seal cracks in concrete with durable urethane caulk. It'll keep water out and protect your foundation and walks from further cracking and eroding. You can do it in less than a half hour.

By the DIY experts of The Family Handyman Magazine

How to caulk wide gaps

Cracks and gaps in concrete are more than just an eyesore. Water can get into the joints, freeze and then expand, making the cracks even larger. Gaps against a house can direct water against the foundation, leading to more problems. Once a year, go around your home and fill these gaps and joints with urethane caulk to prevent problems. The caulk is available at contractor supply stores, well-stocked home centers and hardware stores. For gaps and joints more than 1/4 in. wide, install foam backer rod to support the caulk. You want the rod to fit tight in the joint, so buy it one size larger than the gap.

A word of advice: Keep the urethane caulk off your bare hands and clothes; it's the stickiest stuff you'll ever touch. Wear disposable gloves when you're tooling the joints. If you get some on your skin, quickly wipe it off with a paint thinner–dampened cloth.

How to caulk narrow gaps

Skip the backer rod and apply caulk directly to cracks narrower than 1/4-in.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Caulk gun

Spoon

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Urethane caulk
    • Foam backer rod
    • Mineral spirits

Comments from DIY Community Members

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1 - 5 of 5 comments
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October 19, 2:08 PM [GMT -5]

repairconcretecracks.com has all the info on repairing driveways, patios any concrete

September 21, 2:52 PM [GMT -5]

Thank you for the Step by Step outline. This is extremely helpful for homeowners and cost saving as well.

September 21, 8:07 AM [GMT -5]

I am planning on putting an epoxy finish on my garage floor. However, I have lots of cracks that are hairline to about 1/8".
1. Will I need to enlarge the cracks to get good penetration of the caulk into the cracks? Would it be easier to use a chisel rather than a saw?
2. Is this type of caulk compatible with the various types of epoxy or urethane garage floor finishes available?
4. I can't find a comparison of the various types of finishes available as to ease of installation, wear, touch-up, etc. Do you have any info?
3. Have you done a project like this? I'll happily let you guys use mine as an example!

September 20, 5:02 PM [GMT -5]

Zack,
This sounds good but I cannot get a picture of how this works in my head. Do you have any resources that might show pics or a video of this?

May 29, 1:38 AM [GMT -5]

if your caulking a seam with urethane and want a very sharp clean look try this.
This takes a little extra time but will make a very nice look.
Tape both sides of what you are going to caulk.. stick the tape down and pull it out several feet and pull it tight and stick the end of the tape down. This will make a true strait edge for your caulking.. next apply the caulking as cleanly as you can between the masked joint. Finally take a mixture of soapy water in a spray bottle and spray it on the urethane the soapy water will not break down the urethane. Once you squirt it down take your finger or a spoon and slick the bead down and remove the excess. The soapy water will keep the urethane from sticking to your finger and lets your get a nice slick sharp bead. now remove the tape and there you have it a laser sharp and perfect bead of caulking!

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