Why Builders Saw-Cut Concrete Foundation Slabs

As concrete pours, home builders smooth it out to create the perfect foundation for a custom home. After that, the framing stage of the home build is ready to begin, right? Actually, there are a couple of precautions home builders take before framing to ensure clients have the strongest foundation for their home. 

Before framing, the concrete foundation needs to be prepped. As concrete cures, it shrinks and leads to internal tension. Over time, the internal tension creates unpredictable cracking along the concrete which compromises the integrity of the foundation. Builders are far too familiar with concrete to let this cracking get the best of the build. Cracking is inevitable, but there are ways to control it. 

Concrete crack control is an imperative step for a sturdy build. Shortly after the concrete has dried and cured, home builders saw grooves into the concrete in the pattern of a grid to control how the concrete will crack down the road. These grooves are also known as ‘control joints’, and they tend to line up closely to the piers of the foundation. Each control joint is ¼ of the foundation thickness deep, so if the slab is 4 inches deep, home builders will saw 1 inch deep. Timing for control joints should be anywhere between 4-12 hours after the concrete is done curing. Cutting into the concrete too early could lead to crumbling edges from the saw. When it’s too late, the concrete could have already started cracking down the middle.  

When a concrete foundation is prepared for cracking, breaks in the foundation are predictable. Cutting ¼ of the way into the foundation near support points acts as a guide for cracking when the time comes. As the foundation is cut in a grid pattern, think of the foundation like a Hershey Bar. Each piece is easy to break off thanks to the help of grooves in the chocolate. The same idea applies to concrete foundations.