How Do You Fix Garage Floor Cracks?

Concrete cracks are splits in the floor surface. They run from a hairline to a few inches wide. Concrete cracks are one of the most common garage floor problems. So long as they're cosmetic, concrete cracks are pretty simple to fix.

Clean small cracks with a wire brush, a hammer, and a cold chisel. Prepare a larger crack using an angle grinder with a crack-chasing wheel. Vacuum away the debris. Fill small cracks with RTG Crack Filler. Fill medium cracks with EpoxyShield Patch & Repair. Fill large cracks with Epoxy Patching System.

Before you get started though, diagnose whether the crack is indicative of a structural problem that requires professional help to fix. Go ahead and fix cosmetic cracks yourself.

If you're dealing with more than one kind of concrete repair, read these next:

• How Do You Fix Garage Floor Cracks?
• How Do You Fix Garage Floor Spalling and Pitting?

Find links to the products mentioned in these articles on this site:

• The Best Garage Floor Repair Products
• The Best Garage Wet Vacs
• The Best Garage Project Safety Gear

When Should a Professional Fix a Garage Floor Crack

A minority of cracks are signs of structural or deeper damage. Look for these symptoms of a larger problem:

• one side of the crack is higher than the other
• bulging
• erosion

If you see any of that, you should get a professional concrete contractor to check the problem.

As long as it's not a structural crack, you can fix it yourself.

First, you want to get a sense of the crack's length, width, and depth.

This will help you determine what type of product you want to use and how much stuff you need to repair it.

Why Do Garage Floors Crack?

Most cracks are not structural. They are simply stress fractures caused by the contraction and expansion of the floor.

Concrete contracts in cold temperatures, and expands in warm temperatures. All concrete floors crack. That's just the way it is.

You can learn more about concrete cracking in this excellent article about thermal expansion and contracting on the Penn State College of Engineering website.

Crack Repair Step 1: Clean Out the Crack

The first step in any crack repair is to open and clean out the crack using a cold chisel. This is called “chasing the crack.”

Next, clean out the crack with a brush and vacuum cleaner. Use a simple nylon brush

You should look for and remove any easily crumbled or sandy concrete. This is called “laitance.”

It is a weak area in the original pour and must be removed.

Laitance will not provide a stable surface for the repair to attach to and will possibly cause your repair to fail.

Go at the area with a brush and vacuum again until you are certain you've removed the crumbly concrete.

For longer cracks, you can use a small angle grinder with a crack-chasing masonry wheel. This will create a nice smooth groove and save you lots of time. The angle grinder we like best is on our products page here.

Warning! Angle grinders give off sparks and debris. Wear appropriate safety equipment such as goggles and gloves. Don't assume you know how to use the angle grinder. At least go to Youtube for lessons.

You really want to make sure that you have cleaned out the crack well and that no loose debris and sandy concrete remain. This is the key to lasting repairs.

Crack Repair Step 2: Fill the Crack

For cracks up to about 1/2″ wide, get a self-mixing tube of crack filler. These are great because they work without requiring you to mix batches of filler.

Our favorite small crack repair is RTG Concrete Crack Filler (link goes to Amazon).

It's reasonably priced and is the one I would choose for my own garage repairs.

RTG works with a standard caulking gun. The filler comes with a self-mixing nozzle. It leaves a hard, concrete-like finish.

RTG Concrete Crack Filler Fast Facts

1. Use RTG on cracks up to 1/2 in. wide
2. It's waterproof
3. Can be used on concrete, slate, brick and cement
4. It fills cracks and holes
5. No mixing required – it mixes itself as it comes out of the tube
6. It dries to a milky clear color
7. Use a minimum of an 8:1 ratio caulking gun – 1 lb. of hand pressure translates to 8 lb. of force
8. Check out RTG Concrete Crack Filler on our Product Page

For bigger cracks, you can use either an epoxy kit or a polymerized concrete mixture.

One of the best garage floor crack repair epoxy kits is Rust-Oleum’s EpoxyShield Concrete Patch & Repair. This is a two-part kit consisting of epoxy and sand. EpoxyShield has a good reputation and is easy to use. It dries to a very tough surface that seals the crack with a light gray finish.

Thoroughly clean the concrete crack before mixing the product. Mix the epoxy and sand together on a piece of cardboard.

To use Rust-Oleum Concrete Patch & Repair you need:

1. Rust-Oleum Concrete Patch and Fill
2. Vacuum Cleaner
3. Putty Knife
4. Optional Trowel
5. Gloves
6. Broom
7. Cardboard

Check out Rust-Oleum Concrete Patch & Repair on our Product Page

Rust-Oleum EpoxyShield Concrete Patch & Fill Fast Facts

1. Use Concrete Patch & Repair on cracks up to 1/2 in. wide
2. It's waterproof
3. Can be used on concrete, brick, masonry and stone
4. It fills cracks and holes
5. Mix 2 parts base with 1 part activator
6. It dries to a light gray
7. Use a trowel to spread Concrete Patch & Fill

Check out Patch & Fill on our Product Page

Then fill the crack with the mixture. It is important not to mix too much since it may start to cure before you are finished working. Only mix enough for what you are doing at the moment.

If your garage floor has lots of cracks, one of the best solutions is the three-part Epoxy Mortar Patching System. It has an excellent reputation. It doesn't just fill concrete cracks. You can also use it to repair the driveway (asphalt), wood, and metal.

Epoxy Patching System comes in 25 and 50 lb. pails. Use Epoxy Patching System for cracks up to one inch wide. The Epoxy Patching System is really strong and effective, but you still have to clean the damaged area before applying it. To apply it, you mix the resin, hardener, and aggregate in small batches.

For deeper cracks, fill the crack two-thirds of the way with sand first. Be sure to force the mixture into the crack to remove any air. For the best finish, add sand to the top. Then scrape it off after the mixture cures.

Epoxy Patching System Fast Facts

1. Use Epoxy Patching System on cracks up to 1 in. wide
2. It's waterproof
3. Can be used on concrete, brick, masonry and stone
4. It fills cracks, small holes and pits
5. It is a 3-part epoxy patch
6. It dries to a medium gray
7. Use a trowel to spread Epoxy Patching System

Check out Epoxy Patching System on our Product Page

Sometimes contractors prefer using polymerized concrete rather than epoxy-based solutions to patch cracks. Using layers, you can fill any width crack with polymerized concrete.

Polymerized concrete is easier to apply than epoxy. You mix it with water and then trowel it into the crack. Polymerized concrete also gives you more time to work with the slurry before applying it. Polymerized concrete is not as strong as epoxy, but it is easier to apply.

One of the best polymers is Sakrete's Top ’N Bond Concrete Patcher. It's easy to use and dries to a light gray. It's a good product for small cracks.

Sakrete Top ‘N Bond Concrete Patcher Fast Facts

1. Use one layer of Top ‘N Bond for each 1/2 in. width of crack. The mixture will settle toward the bottom of the crack. Wait for the material to harden before adding a new layer.
2. It's waterproof
3. Can be used on concrete, brick, masonry and stone
4. It fills cracks, small holes and pitting
5. Mix with water to form a smooth paste
6. It dries to a medium gray
7. Use a trowel or a brush to spread Top ‘N Bond
8. Check out Top ‘N Bond on our Product Page

The Appearance of the Fixed Crack

Simply put, you will not match the color of your existing floor. Many of the negative reviews I have read about products like this revolve around how it was ‘too dark” or “too light.” If you are worried about the color then you will need to paint the floor.