Cantilevered countertop supports up to 960 pounds demonstrating the power of proper reinforcing

Students of Cast in Place Concrete Countertops 101 produced a cantilevered countertop that supported up to 960 pounds.

The countertop used Jeff Girard's mix design, steel reinforcing near the bottom to counteract the typical flexural forces at the bottom of the countertop, and TechFab's CT-300 carbon grid near the top to counteract the flexural forces produced when a cantilever section is loaded from the top.

Jeff placed 16 60-pound bags of sand on the 12" long cantilever, and no cracking occurred. "I stopped adding bags because they got too high, and I felt it was dangerous for me to continue lifting bags above my head.", Girard said. "Based on my calculations, I know I was close to the failure point of the countertop, but I didn't reach it."

This countertop had cured for several days before loading. The bags remained on the countertop for 3 weeks, with no cracking.

At another Cast in Place Concrete Countertops 101 class, taught jointly December 12-14, 2005 by Jeff and by Bob Harris of The Decorative Concrete Institute, students produced cantilevered countertops that supported a person's weight after only 1 day.

Dubious students were convinced when they stood on the end of the cantilevers and nothing happened.

Again, the countertops used steel and carbon grid reinforcement, placed at the top and bottom respectively. Some countertops used Jeff's mix design; one used Encounter from The Stamp Store.

The demonstration brought home the point to students that if they learn the engineering behind proper mix design and reinforcement, they can be totally confident in their countertops. With Jeff's engineering expertise and Bob's master craftsmanship, students of this class learned how to build stunningly beautiful, structurally sound countertops.

Bob stated, "My experience with concrete has taught me that you have to understand both the performance and the aesthetics of the material in order to produce quality work for your clients. Jeff totally understands countertop performance."

For more information about Bob Harris and the Decorative Concrete Institute, visit

For more information about Jeff Girard and the Concrete Countertop Institute, visit