Temperature changes cause concrete to expand or shrink. That often leads to cracks, which lead to extensive structural damage over time. A concrete expansion joint is placed to allow the materials to expand or contract without damaging other structures.
What are the expansion joints?
Contraction joints are used to regulate cracks in the concrete. The joints may be tooled into the surface of the concrete or sawed into hardened concrete. However, the longer the sawing takes, the greater the risk of cracks in the concrete.
What do the joints do?
A concrete expansion joint separates the slabs and concrete from other parts of the structure, thus allowing each structural component room to move. The joint makes the thermal expansion and contraction possible all while eliminating any possible strain on the system or other parts of the structure.
Do you need them?
If your home structure has areas where two consecutive placements of the concrete meet, those areas require concrete expansion joints. For the best time to place the joint, choose the end of the day.
How do you place them?
For placement tips, you should go over the following reminders:
- If you want to ensure maximum joint spacing, make sure it is 24 to 36 times the thickness of the slab.
- Place the joints about 10 feet apart, with 15 feet as the maximum distance.
- For contraction joints that use a joint groove, make sure the dept of the joint is at least one-fourth of the thickness of the slab.
- If you opt for saw-cut joints, make sure these are done within 4 to 12 hours after your contractor finishes the concrete. Any longer and cracks could develop in the concrete.
- If you are working on industrial floors, steer clear of keyed joints.
- If the slab comes with a wire mesh, cut the mesh across the contraction points.
To learn more about concrete expansion joint, visit Trim-A-Slab.com