Applying the stencils

After crews place the concrete, they screed, float and edge the slab in the usual manner and then place the stencils on the surface while the concrete is still wet but free of excessive bleed water. Placement requires two people, with one person holding the stencil roll while the other person holds the uncoiled end on the opposite side of the slab. Once the stencil is laid down atop the slab, it's plastered to the surface with a special stencil roller.

The stencil is placed and worked one strip at a time. Because the stencils are die cut, the strips must be aligned in a specific manner to ensure pattern continuity, similar to aligning strips of patterned wallpaper. After the entire slab is covered, workers use a pair of scissors to trim the stencil to about 1/8 inch inside the form boards (this allows for the stencil to swell a bit). A hand float is then used to stick down the edges.

Applying stencils to existing concrete - sandblasting or acid etching?

These two popular techniques for stenciling hardened concrete involve removing a very thin surface layer of concrete, leaving the areas masked by the stencil intact to create a raised, three-dimensional pattern. In the case of sandblasting, you adhere the stencil to the concrete, then go over the area with a sandblaster, keeping the nozzle at least 12 inches above the surface. With etching, you brush-apply a gelled acid over the exposed areas not covered by the stencil, using a product that's thick enough so it won't bleed underneath.

Both techniques, especially sandblasting, can be tough on the stencil itself, so the material needs to be durable enough to stand up to the process. You'll also need to use a stencil with an adhesive backing that prevents movement. Be sure to ask the manufacturer if its stencil products are suitable for these applications. Brickform Rafco Products, for example, makes self-adhesive vinyl stencils designed to withstand sandblasting and light shotblasting. They are available in many stock patterns as well as custom designs.