Building Expansion Joint Systems

Mixing concrete in a bucket
What You'll Need
Expansion joints

The expansion joint is a fitting in the wall which is designed to absorb shocks such as heat-induced expansion and contraction of walls, any kind of noise vibration, and even defend against earthquake damage. They are often used between structures, for example connecting buildings separated by a sidewalk, or running underneath paving to connect pipework. The expansion joint is also used in buildings to help prevent cracks from appearing in concrete and cement. For example, if you wanted to use an expansion joint on the surface of a driveway, this would help to stop the changes in temperature from summer to winter from causing splits in the concrete. You can easily install expansion joints anywhere you choose.

Step 1 - Prepare the Joints

When you are nearly ready to add your concrete to the wall or pathway, then you should start constructing your expansion joints. You will need to have a joint which is the same depth as the concrete which is being poured, although this should be easy to assess from the size of the concrete frame you have constructed. You may also make your expansion joints out of wooden lengths, cut down to a suitable height, keeping in mind the thickness of the concrete. Use your hacksaw to remove any excess lengths from your expansion joint.

Step 2 - Pour the Concrete

pouring concrete in a basement

Once you have prepared the joints, you can start to pour out the concrete. This is the best time to install your expansion joints, as the concrete is pliable, and you can move the joints until you find the right place. The ideal spot is between the finish of one concrete slab, and the beginning of the next. You should create one slab, add an extension joint, pour the next slab, and then repeat until finished.

Step 3 - Fit the Joint

Although it is easier to put the joint into position when you are pouring the concrete, you can also wait until your slabs are almost hard, and then you can use a trowel to press the slabs apart. This space should be just enough to fit the expansion joint, and allow movement. You could also just leave this small gap between the slabs, although this could expose them to water damage. Press down the expansion joints until they are tightly nestled in the slab.

Step 4 - Add the Joint Later

A bigger problem arises if you are adding the joint after you have already fitted the concrete. You will need to remove all of the concrete where the joint will go using a concrete saw. Mark out where you want the expansion joint to go, and then cut out these sections. You can then position the expansion joint against the concrete, and add a layer of cement where any gaps have been left. This is not a very good idea for building an expansion joint system, and you are better off installing the joints before the concrete has set.