Understanding The Three Types Of Concrete Slab Joints

As your new concrete slab is poured for your commercial building remodel, it is essential that you understand the three different types of concrete joints that will be used and their purpose.

These concrete joint types are:

  1. construction joints

  2. contraction joints

  3. isolation joints

Here is some information about each type of concrete joint to help you understand their necessity, use, and how they are created:

Concrete Construction Joints

Construction joints in a concrete slab occur where your concrete contractor needs to stop pouring the cement due to weather, materials shortage, or time constraints. The construction joint is formed at the edge of the pour area using a plastic, steel, or wood key joint or simple butt joint.

Key joints are more complex and are necessary where there will be vehicles driving on the slab. For walkways and office spaces, a simple butt joint is all that is necessary.

Concrete Contraction Joints

Contraction joints are cut into all concrete slabs using a concrete saw. Contraction joints are needed to prevent concrete from unnecessary cracking. Since concrete is a porous material, it needs room to shrink as it cures and expand when it absorbs water.

Cutting contraction joints is vital and their spacing depends upon many factors, including:

  1. the depth of the concrete

  2. the concrete's substrate makeup

  3. the concrete mix being used

Thinner concrete mix and a less desirable substrate make it necessary to put more contraction joints in the slab and place them closer together. A deep concrete slab can be scored and allowed to crack vertically as it cures.

Concrete Isolation Joints

Isolation joints are used in concrete to separate the new slab from columns, plumbing, and walls. This is vital because construction materials of different compositions act differently as they naturally contract and expand as the temperature and humidity changes from one season to another. To keep the materials from pushing on each other and causing damage, isolation joints are created between them.

Concrete isolation joints are created by placing a plastic material around the base of anything that the concrete slab would otherwise come into contact with. When the concrete has cured, then the isolation joints can be sealed for cosmetic purposes at the surface.

For Additional Information

For further information about the joints necessary in your building's new concrete slab, you should speak with your remodeling contractor, who will be happy to answer all of your questions.

Talk to a business like Red Rock Construction to learn more.


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