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Overlaying Microtoppings on Concrete Floors
Overlaying over an existing overlay can be problematic. Knowing the existing overlay, how it was mixed and knowing if the substrate was done properly are key to a completing the decorative concrete floor.
by Susan Brimo-Cox
How much of a gambler are you? When you’re considering applying an overlay over an existing overlay, most experts will tell you not to do it — the risk is too great.
The fact is, unless you’re the contractor who applied the existing overlay, “you’re banking on what the guy in front of you did,” says Marshall Hoskins, senior technical representative at Specialty Concrete Products Inc. “It’s a roll of the dice.”
Seth Pevarnik, manager of technical service at Ardex Engineered Cements Inc., agrees. There are three major areas of concern, he says. You may not know what the existing overlay product is. You don’t know if it was mixed correctly. And you don't know if the substrate preparation was done correctly.
Even if you do a test area, you can’t be 100 percent certain your overlay will work over the existing one. Why? “What works in a small area may not work in a large area,” Pevarnik points out.
Overlay manufacturers don’t want to assume the risk either. As Scott Wyatt, director of technical services at Floric Polytech Inc., explains, “When you’re doing overlays, the first thing a manufacturer will tell you is to rip up what was there. They don’t want to guarantee that their product will adhere to someone else’s.”
With those cautionary caveats acknowledged up front, there may be times when you’re asked to apply an overlay over an existing one. Can it be done? Of course. But you need to limit your risk and liability.
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