How to Repair Cracks in Concrete?

While concrete is one of the most durable and long-lasting construction materials available, it’s still subject to cracking over time. Repeated freezing and thawing over winter, the ground below it settling, and tree roots growing can all lead to unsightly cracks in your garage floor, driveway, or sidewalk.  

Luckily, repairing cracks in concrete is a simple and low-cost job that most DIYers will have no problem with. Hiring a contractor to repair cracks in concrete can be costly, so doing it yourself will save you both time and money.

It’s also best to fill cracks before they expand and become more difficult to repair.

All that’s needed to repair most cracks in concrete is a few basic tools, a concrete repair product, and a little elbow grease. Let’s take a look at what it takes in detail.

Patching Cracks in Concrete – Guide

Before you get started, you’ll want to make sure you have all the tools and materials necessary to repair your concrete cracks.

Anytime you’re working with concrete and concrete products, you’ll want to have everything you need before beginning. The last thing you want to happen is to realize you don’t have enough concrete patch mix halfway through the job.

Tools & Materials Needed

Step 1: Assess Cracked Area

The first thing to do is assess the cracked area. The repair process will differ depending on the size of the crack and the level of damage to the slab.

surface cracks in concrete
Fine surface cracks like these can be repaired by applying a concrete resurfacer.

Small surface cracks that don’t penetrate very far are the least concerning type. You’ll often see these spider web shaped cracks on larger slabs that have dried too quickly. This phenomenon is called ‘crazing’ and is not an indication of serious structural damage. These cracks can be repaired using a resurfacing product which is applied with a concrete broom.

If you’re dealing with a larger crack, then the repair procedure is a little more complex.

A crack under ¼” wide can usually be repaired with an epoxy or concrete caulk specifically designed for this. Many of these products are designed to shrink and expand with the concrete, so they’ll prevent further damage later on.

Cracks from a ¼” to 1” may be an indicator of more serious damage, but can be patched with a mortar mix or pre-mixed concrete patching compounds.

Step 2: Clear Loose Concrete

Use your hammer and cold chisel to knock loose any weak or cracked pieces that are inside the crack. This will also widen out the gap – which will make the patching compound adhere better.

If the crack is particularly narrow, then you’ll need to widen the entire thing to make it large enough to apply the patching compound.

Step 3: Clean Crack and Prep for Patching

Once you’ve cleared the loose concrete and figured out what type of patch product to use, you’ll need to thoroughly clean the crack from debris. Cracks in concrete act like magnets for weeds, dead leaves, pebbles, and other yard waste, so you’ll want to get rid of these before patching.

Use a pressure washer or garden hose and spray nozzle to clear out as much debris as possible. Then use the steel brush and broom to get rid of any leftovers.

Step 4: Apply Concrete Filler

Next, you’ll want to apply the concrete filler. Masonry and concrete filler products come with a wide variety of applicators including caulk tubes, squeeze tubes, and buckets.

cracked concrete driveway after repair
Cracked concrete after repair. [Source: Decorative Concrete Kingdom]
The tube-style applicators allow you to squeeze the filler directly into the bottom of the crack. You may need a caulking gun to get this done effectively.

Make sure you push the filler all the way into the crack, so there are no gaps or air pockets left. When this is done, smooth it out with a trowel or putty knife.  Scrap off and remove any excess if necessary.

Concrete patching products differ significantly in terms of dry times and application methods, so consult directions on the package for specifics.

Step 5: Allow the Filler to Dry/Cure

When you’re satisfied with the look of your patch job, you’ll need to let the concrete filler dry and cure overnight. Once again, the drying and curing times will vary widely depending on the product specs, so make sure to check the back of the package.

Step 6 (Optional): Coat with Sealant

While it’s not strictly necessary, coating your patch job with a few coats of clear polyurethane sealant. This will help protect the crack from further damage, give it a nice professional-looking finish, and will last for years before requiring reapplication.

These sealers can be used for both exterior and interior applications and will make the surface nearly impervious to liquids after application.

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