Surface Prep for Concrete
Proper surface prep is essential to success application of a microtopping over a concrete surface. Profiling is essential, and moisture vapor, alkalinity, cracks and seams must all be dealt with.
by Mike Dawson

If a microtopping looks good on the surface, don't be too impressed until it's proven to perform. When it comes to these thin overlays, beauty is only skim deep, but ugly goes all the way to the slab.

In other words: A beautiful microtopping over concrete is only as good as its preparation. A poor substrate will show its character flaws sooner or later, costing money and making a contractor look bad. That's why the voices of experience advise spending more time on prepping the surface than on the microtop application itself. "We do more prep and cleaning than we do decorative work," says Wes Vollmer, a consultant and owner of Alternative Finishes, based in San Antonio, Texas.

A microtopping is thin by definition, less than 1/8-inch, and is often applied by squeegee, trowel or broom. Some, like CemLogic MT-200 from Floric Polytech, can be sprayed.

But first the concrete substrate must be free of any bond breakers, including grease and solvents spilled on the surface, as well as alkali and moisture generated from within the concrete. So whether your substrate is an old garage floor or a fresh pour, you have a lot to consider before applying a microtopping.

"No single factor accounts more for the success or failure of an installation than substrate preparation," says Bruce Newbrough, director of technical services for Ardex Engineered Cements. "Regardless of the underlayment or patching compound used to level, smooth or repair a substrate's surface, the ultimate strength of the bond will only be as strong as the substrate itself."