Many seemingly perfect concrete walls have cracks that show up months, even years later, affecting not just the aesthetics but also the integrity of the wall itself.
Concrete can and should be controlled by joints in spite of the fact that cracking is a natural feature of concrete. Whether you decide on concrete form rental or choose to purchase your forms, it’s good to start planning out your joints when you select your formwork.
Three Types of Joints to Prevent Concrete Cracking
There are three types of joints in concrete that prevent unwanted cracking. These consist of contraction, expansion, and construction joints. Employing the correct joints in your next pour will make sure the wall you build stands for years to come.
Contraction joints combat cracks that form because of changes related to shrinkage and temperature. Joints are created by fastening strips of wood or other material to the inside of the concrete. This protrusion from the form creates a grooved joint in the concrete. These joint grooves in the concrete should be sized to reduce the thickness of the wall by one fourth. Place sealant on the cracks to resist weather damage and attach an asphalt felt strip to the waterproof adhesive to protect the joint below ground.
Joint spacing varies depending on different factors such as wall height, thickness, and opening placement. In general, contraction joints should be not be spaced more than 30 feet apart. Joints should be placed in line with window and door jambs where possible.
Also known as isolation joints, expansion joints allow movement between two adjoining walls. Expansion joints can be complex mechanical systems or simple smooth dowels, though they are usually just asphalt impregnated fiber boards with a thickness of ½ to 1 inch. Verify what type of joint your plans call for in the planning stage before placing them.
Construction joints allow for pouring in sections when executing large pours. They are sometimes placed on purpose and other times they are placed out of necessity as equipment fails or concrete runs out in the middle of a section.
The key to connecting a construction joint is to make it as strong as the wall would have been without the joint. This means adding sufficient steel reinforcement to tie the placement at the joint as well preparing the surface so that the new concrete bonds well to it. If construction joints can be placed where expansion and contraction joints would be placed already that is an even better solution.
Renting the Right Concrete Form for the Job
Always remember to place any joint in a place that will not inhibit wall strength. If you can incorporate joints to blend in with the structures appearance that is an added bonus.
Putting joints in the right place is important and should be planned out in conjunction with the type of concrete forms that you will be using. Forming America takes the hassle out of concrete formwork rental. You can have confidence in our forming equipment’s integrity since we make sure that all forms are within specifications before we rent them to you. Plus, we deliver right to your jobsite. Contact Forming America or call 1-888-993-1304 to rent your concrete forms today.