Waterproofing and sealing expansion joints

Expansion joints help maintain the integrity of concrete for the longest possible life. Here are some fundamental techniques for waterproofing and sealing expansion joints.

Importance of expansion joints

Expansion joints separate concrete slabs in sidewalks and driveways. They are usually made of wood or fiberboard bonded to asphalt.

Expansion joints help prevent drying concrete from pulling apart as it shrinks and assist in dealing with temperature changes. The joint gets smaller when concrete heats and expands and larger when concrete gets cold and compresses. They also help concrete movement adjust to underlying soil condition changes due to temperature and water so the concrete doesn’t break up.

Minor risks associated with unsealed joints include unsightly weeds growing up through gaps in the expansion joint and missing expansion joints, which can be a trip hazard. The most significant risk is that air, water, and insects can remove soil from underneath the concrete slab, leading to the slab cracking from vehicle weight.

Steps for effective waterproofing

To replace expansion joints, you can use multiple materials, sealants, and techniques. Here is one general method.

Removal and cleaning

First, remove the old expansion joint material. Then, clean out the groove with a screwdriver, chisel and hammer, wire brush, air compressor, or leaf blower. You want the expansion joint free of loose debris and paint.

Refilling and sealing

Measure the depth and width of your expansion joint. You will need to lay in a backer rod, which is a foam rope. Try to get a backer rod about 1/8″ wider than the expansion joint. If the joint is larger than your backer rod, you can fill the joint with all-purpose sand up to 1/2″ below the surface. Then, place your backer rod 1/2″ below the surface and brush the excess sand away.

Find a good self-leveling sealant and use a caulking gun to fill the crack. If needed, use painter’s tape to keep your line clean. For any areas where the edge has been broken or chipped away, try to remake the line with the right liquid fixative. Let the sealant dry before you put any pressure on it, and it should be good.

Do your expansion joints need repair or replacement? JK Industries provides a wide variety of concrete restoration services, including concrete slab repair and replacement. Contact us today.