How To Reseal Driveway Expansion Joints

Introduction

If you have a concrete driveway, it's likely comprised of multiple slabs. The gaps between these slabs are called expansion joints.

The number of expansion joints varies with the size of the driveway — the larger the driveway, the more joints you'll have. But whether you have one or a dozen, all need occasional maintenance.

What Are Expansion Joints?

Two types are commonly found on concrete sidewalks and driveways: expansion joints and control joints.

Expansion joints are the gaps that provide room for the concrete to expand with warmer temperatures or when the ground shifts. This reduces the risk of cracking.

Control joints give the concrete surface a safe place to crack, controlling the location and extent of any cracks that do occur.

Can I Seal the Expansion Joints in my Driveway?

Absolutely. During construction, expansion joints are filled with material to prevent water infiltration. (I most often see fiberboard, but different contractors use different materials.) As this material wears out, it must be replaced with a new water-resistant barrier.

The easiest way to do that is with a little caulk and backer rod. This prevents water from getting under the concrete slab while still providing enough give to let the slab expand and contract without damage.

Should I Seal Driveway Expansion Joints?

Yes. Expansion joints need to be resealed as part of your regular maintenance.

Because expansion joints go all the way to the ground, water that gets between the slabs can wash away the underlying soil. The resulting voids can cause the slab to tilt or crack.

Control joints, however, do not go all the way through the concrete slab, and they typically don't need to be caulked. In the driveway I worked on, some of the control joints were particularly deep and would channel water into the expansion joints. So they needed to be caulked as well, though I left the shallower control joints uncaulked.

When to Fill Expansion Joints

You can typically determine if it's time to reseal by looking at the joints. If the existing filler is worn enough to allow water to get between the slabs, or if it's missing entirely, it's time to refill the joints.

Fill the joints when no rain expected for 24 hours and the temperatures fall within the caulk's installation directions. In general speaking, any time other than winter is fine.

What is the Best Sealant for Driveway Expansion Joints?

You'll likely use self-leveling or non-sag. Non-sag is similar in consistency to the caulk you've likely used for windows, doors or tubs. Self-leveling is more fluid and, as the name implies, will level itself.

There are several brands to choose from. I used three to demonstrate the difference in coloration and use.

I used Sika and Quikcrete self-leveling caulk. The Sika was more liquid and self-leveled faster and easier. However, the second tube of Sika separated and came out discolored. The Quikcrete self-leveling caulk was more viscous and went on slower, making it a better choice for gently angled surfaces. Both products had a distinctly smooth and shiny appearance. The Quikcrete was a slightly darker shade of gray.

For non-sag caulk, I went with Saschco Slab. It was easy to work with and had a darker gray tone than the other caulks. It was also textured to look like concrete.