Concrete countertops bring elegance and custom styling to the kitchen with colors, profiles, and patterns to suit any design.

Concrete Countertop Basics
A concrete countertop mix includes sand, stone, and cement along with proprietary ingredients that are unique to the manufacturer. Cement is mixed according to the desired outcome. “If the countertop has to cantilever out, for example, it has to be extra strong,” says Stephen Rosenblatt, president of Sonoma Cast Stone of Petaluma, Calif., which has 20 different formulas for their mixes.

Concrete tops are cast in thicknesses from 1½ inches to about 2 inches. Countertops that are too shallow can curl while curing, but concrete forms are often reinforced with rebar or wire mesh for strength and stability. Dyes penetrate the concrete completely for integral colors that won’t fade over time and sculptural properties allow for any edge profile.

Curing—a process that involves a chemical reaction between water and the cement—is regulated. A concrete surface must be kept moist as it cures so that crystals will grow and harden to create quality concrete. Moisture levels are maintained in various ways, including tenting the concrete to maintain consistent humidity levels. When completely cured—a process that can take up to 28 days—a penetrating sealer and wax are typically applied to this porous material.

Depending on thickness, countertops weigh 16 to 23 pounds per square foot. Many manufacturers won’t fabricate countertops over 10 feet in length because a longer top is difficult to muscle around the shop and install in a kitchen. Longer tops can be cast in place or cast in separate sections and installed.

Concrete Cautions
Concrete countertops have been around since the late 1970s but demand has grown as improved technology and skills have brought better results. Homeowners must be sure their contractors understand the principles of concrete, says Jeffrey Girard, P.E., president of Concrete Countertop Institute, Raleigh, N.C. Girard, a licensed professional civil engineer, started the institute and its contractor training programs to provide more information, guidance, and hands-on learning for concrete countertop fabricators. When interviewing contractors, ask for a product sample and perform your own tests to see how it stands up to heat, abrasion, cutting, and staining. Also, ask for customer references so you can view countertops that have seen use.