How to Make Expansion Joints When Pouring Concrete Slabs

by Renae De Leon; Updated September 26, 2017

Expansion joints, or isolation joints, are what are known as control joints. They are added to concrete slabs to provide space for expansion and settling, and to control where cracks develop. Expansion joints are usually used to separate the concrete slab from another object, such as a wall or column. When you are pouring concrete slabs for your business, ensure that your expansion joints are properly positioned and designed so that your slabs don't crack, crumble and heave, and so they don't damage another structure.

Items you will need

  • Plastic
  • Cork
  • Rubber
  • Neoprene
  • Asphalt-treated fiberboard
Step 1

Determine the height of the concrete slab from the base of the sub-base to the top of the finished concrete. This is the height your expansion joint will need to be. Determine the length of the joint. For example, if you are putting in an expansion joint between your exterior wall and a concrete slab, measure the width of the tentative concrete slab. This will be the length you will need to cut your expansion joint material to.

Step 2

Cut your expansion joint material using the measurements you came up with in Step 2. Place this material on the inside of the concrete form in the position where you want the joint to be.

Step 3

Pour your concrete in front of the expansion joint material so that it holds the material in place. Pour the rest of your slab. Once the concrete has cured, remove the concrete form.