How to Fix Cracks in Concrete Driveways and Sidewalks

sidewalk crack

If you have an older concrete driveway, path, or sidewalk, you may wonder how to fix those cracks that often appear on the surface over time. Fortunately, this is an issue that you can easily repair yourself.

The biggest culprits of cracks are the weather and the changing of the seasons. Over time, the freeze and thaw cycle causes the concrete to expand and contract, resulting in cracks.

Another cause are roots from a nearby tree pressing up on the concrete from underground.

And if we’re talking about your driveway, cracks could come from many years of large, heavy vehicles driving over the surface.

No matter what’s causing your concrete cracks, the repair is basically the same: ideally using a flexible caulk with some give to it.

Plan to do the job on a warm, sunny day. Summer is your best chance, though, and is usually the season most people prefer for these types of repairs.

Tools and materials
  • Hook knife or another tool for clearing debris and vegetation out of the crack

  • Leaf blower or a blower powered by a compressor

  • Caulk intended for use in concrete that will be walked or driven on. We recommend Slab caulk, because it’s extremely stretchy and perfect for this application

  • Backer rod, which you need if the crack is one-half inch or deeper. This comes in several thicknesses, so select the size most appropriate for the crack. This is sometimes called filler rope

  • Screwdriver or other narrow, blunt metal tool

  • Caulking gun

  • Small container of clean water

  • Foam brush (optional)

1. Clean out the crack

Using your hook knife or another tool, scrape and loosen up any dirt, vegetation, and/or debris. Then, use a leaf blower to clean the area.

2. Install backer rod

Insert the backer rod by hand, and run it the full length of the crack. Next, use a screwdriver or other blunt, narrow metal tool and tuck the backer rod tightly into the crack.

3. Install the caulking

Squeeze a bead of caulk along the full length of the crack. Be generous with it, but try to install it as evenly as possible.

If you use Slab caulk, you’ll see it looks a lot lighter than the surrounding concrete. But as it hardens and cures, the color starts to blend in very nicely, becoming barely noticeable over time.

4. Smooth out the caulking

You can use a foam brush to do this, but sometimes it’s easier to use your finger. Just dip your finger in water, and run your finger along the bead of caulk, smoothing it out carefully as you go. Periodically dip your finger in the water as you go to keep your finger wet.

Once you’ve smoothed out the caulk, check the manufacturer’s instructions for the curing time. Usually, it will be a short period of time before the caulk “skins” over but a longer period of time for it to cure — often days or weeks. The manufacturer will also tell you the time frame before you can walk and/or drive on the caulk.

Follow these steps and you can fix most cracks in your concrete driveway, path, or sidewalk.

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