Spray-down systems have become a top choice for transforming gray, unsightly concrete. Through a combination of various coloring, patterning, and texturing methods, this system creates infinite design possibilities. Spray-down systems provide a durable, skid-resistant surface. They are ideal for projects where complete concrete removal and replacement is not an option, including pool decks, patios, driveways, sidewalks, and balcony decks.
Preparing the Surface
As with all overlays, spray-down systems require some type of profiling, either chemical or mechanical. If you plan to use acid etching, make sure to neutralize any remaining acid residue with a solution of water and ammonia or baking soda. Chips, spalls, and minor cracks in the substrate must also be repaired.
Some spray-down systems require priming of the prepared substrate surface before topping installation. If the system does not require a primer you will need to prewet the substrate to obtain a saturated surface dry (SSD) condition. To fully saturate a dry substrate, constant wetting for a minimum of four to six hours is necessary.
Mixing
Spray down systems are available in both single- and two-component types. Mixing procedures are similar to those used for microtoppings. First add the proper volume of liquid (water or polymer) to a five-gallon bucket, then slowly add the powder while simultaneously mixing with a paddle drill until thoroughly blended. Always keep a spare drill on hand as backup.
Applying the Base Coat
After allowing the primer to dry for the recommended amount of time, put down a base coat of the spray system to fill in minor pits and cracks and to improve bond. The quickest way to apply the base coat is with a rubber or metal squeegee or with a hand trowel. Depending on jobsite conditions, a minimum of two hours drying time is necessary before the second coat can be applied.
Applying the Texture Coat
Use a random motion to spray the texture material straight down onto the substrate rather than at an angle. Hold the sprayer 2 to 3 feet above the surface. A popular spray-applied texture is a knock-down finish, so called because it involves knocking down with a trowel the high peaks that result from the spray application to achieve a lightly textured surface. This is a two-person process, with one spraying and another wielding the trowel. On surfaces where greater traction is needed, the knock-down may be skipped.
Color Options
Most colored spray systems use an integral pigment. Color layering can be achieved with topically applied color from chemical stains, tinted sealers, or multiple layers of the spray-down material in contrasting colors. A technique I use is to apply the first coat of base color, wait until it is dry, then lightly mist on an accent color of spray material.
Using Stencils
The most common type of stencils used in conjunction with spray down systems are made of plastic-coated fiberboard. First, apply a colored base coat, and then after it dries apply the stencil to the basic layer followed by a spray application of texture coat in a contrasting color. Once the stencil is removed the base color appears as a grout joint. Wait several hours to remove the stencil, or until the top layer has properly cured.
