Control Joint Spacing Guide

When working with concrete, control joints are an important part of the process. Control joints are used in the planning of cracks in the future. They allow for movement according to temperature changes, atmospheric conditions, and overall use. Most concrete walls, sidewalks, and other types of construction is going to crack. With the use of control joints you have some control over where the cracks will happen. Here is a simple guide to help you understand these control joints a little better for your next cement project.

Proper Spacing is Important

When it comes to controlling the cracks that are in the concrete you must adhere to a certain spacing guideline. As a general rule you should space the control joints no more than two or three times the thickness of the actual concrete slab. For example, if the slab is 8 inches thick you would space the control joints at least 16 feet apart. In smaller slabs, this spacing would also be smaller. 

Depth of Control Joint is Also Important

As with the spacing of the control joint, the depth of which they are made is also just as important. The control joint depth should not be any less than 25 percent of the actual depth of the concrete slab. This means that a slab that is 4 inches deep should have control joints that are 1 inch in depth. 

Cutting Control Joint

The easiest way to cut control joints into the concrete is as soon as it has been poured and sets up a little. Grooving tools will do this without any problems. If you must cut the control joint into the concrete after is has hardened, a cutting tool with a diamond blade will help to do the job. Just make sure it is at the right depth and use water to keep the blade cool. Either way, the concrete control joint must be cut into the concrete within 12 hours of it drying and setting up. 

Placement Should Be Hidden

When working on a slab for a basement, or a garage, you can place the control joint in an area where it will not be easily seen. Set the control joint near walls, or under carpeted areas. This way they won't be seen through casual observations. 

Plan Control Joints

If you are working with a blueprint of a home, garage, or other type of building, there will be control joints already drawn on the plan. Sometimes these plans do not have enough control joints built into them. Look over the plans first and add them if they are needed. However, if you are building something from scratch, make up a plan where the control joints will be located. One rule of thumb is to avoid re-entrance corners. Joints should run across the corners instead of into them. 

Take Control Joints Seriously

One of the main things about concrete control joints is to take them seriously. By doing so you are making sure that the concrete slab is not going to crack in areas where you do not want it to. These cracks can cause structural damage if in the wrong areas.