A Modello Designs pattern and Colormaker Sgraffino fine overlay with integral color and dyes. Photo courtesy of Ramcrete.

Staying on Top of Decorative Concrete Stenciling

Several companies have developed polymer-modified concrete toppings formulated specifically for stenciling. Bob Harris of the Decorative Concrete Institute in Temple, Ga., says these products differ from general-purpose overlay materials in two ways — the polymers that are used and the gradations of the aggregate. “A lot of times with a traditional overlayment, maybe even a microtopping, it’s a much finer sand,” he says. “In some cases they even have ground sand, which is silica flour.” The special-purpose stencil toppings, on the other hand, generally use slightly coarser sand.

Many times, these types of products are air-applied with a hopper gun. However, some manufacturers suggest troweling as an alternative.

Application techniques and final properties of special-purpose stencil toppings differ from general-purpose overlays in several ways.

Thickness
One way stencil-grade toppings differ is thickness. “The specifically formulated ones are designed to go down very thin,” says Matt Shields of Ramcrete in Owasso, Okla. He often uses Colormaker’s Sgraffino, which is troweled on in ultra-thin coats that are less than 1/32-inch thick. More commonly, stencil-grade toppings are applied at thicknesses of 1/32 inch to 1/8 inch, compared with general-purpose overlays, which are applied at thicknesses of 1/4 inch to 3/4 inch. The stencil-grade products can be built up in layers if a thicker surface is desired.