Concrete Countertops Mixes, How-To and Tips

Concrete countertops are more than a trend. As more and more homeowners and designers specify concrete countertops in new homes and in remodeling projects, concrete is making a permanent place for itself as a material of choice for countertops across the country.

Of course, the cost of countertop materials varies around the nation, but if you compare concrete to other popular products what you would probably find is this: A typical tile countertop is less expensive than a concrete one. Solid surface materials run about the same or a little less. Granite and marble often cost more.

The advantages of concrete as a countertop material range from its physical characteristics to aesthetics — from its durability to its flexibility. As Michael Karmody, a founding partner of Stone Soup Concrete in Northampton, Mass., points out, “With concrete, you can have any shape you want. Concrete is a structural material; you can vary textures. We can grind it to expose the aggregate or leave it as it comes out of the mold. … It’s easy to inlay [and] emboss textures. It’s a really good sculptural material.”

Creative potential aside, there are some who may wonder about the weight of concrete countertops. However, weight really isn’t an issue any more than natural stone. Karmody explains that a granite countertop weighs about 22 pounds a square foot. Concrete 1.5 inches thick weighs about 18.5 pounds a square foot; at two inches thick it weighs about 25 pounds a square foot.

Concrete has some disadvantages, such as its vulnerability to staining and it not being as rock-hard as granite. As Fu-Tung Cheng, principal and chief executive officer of Cheng Design in Berkeley, Calif., philosophically observes, “I frequently tell people that you have to be objective about concrete. You have to play to the strengths.” Fortunately, the contractors who have enjoyed the challenges of creating concrete countertops for many years have worked out many of the “bugs,” and the results are more reliable and consistent.

Concrete countertops are not for everyone, though. “Concrete has an earthy aesthetic — mottled color, some crazing. It’s OK for it to have some patina,” Cheng says. If people want “slick,” concrete is probably not the material for them.

“There are criteria people use in selecting countertop materials — granite is a typical standard,” Cheng explains. It boils down to the issue of what constitutes what’s acceptable, he adds. “Contractors who experiment or push the envelope will help set the standard of what’s acceptable.”

How-to depends on whom
Each contractor who has experimented and refined his or her concrete countertop technique has found individual solutions to this creative process.

Karmody says his “mix design is not too different than what they used in the Hoover Dam,” but he does use admixes, fiber and fan-shape reinforcement, and other innovative techniques to create unique products for each of his clients. “Everybody wants something different, so all colors are custom and are included in our standard product.”

His custom finishes include marbling colors, adding dye late in the mix so the colors appear like flames in the finish, acid etching, and embedding objects, such as sea shells, stones, brass and voids for drainboards.

Steve Eyler, owner/operator of Eycon in Myersville, Md., created his mix design based on a Glass Fiber Reinforced Concrete design — tweaking it to work with and enhance his product. “It gives it more structural and flexural strength. [I’m] not as concerned with compression strength, but more concerned with flexural strength.”

Another technique Eyler has been perfecting is using sandwich panels to reduce the weight when a thick slab is required. He has developed specific procedures that allow him to sandwich in a lighter material, such as Styrofoam, inside the center of a thick slab without compromising the countertop’s structural integrity or finish characteristics.

Many contractors prefer to pre-cast concrete countertops for many reasons: It is less risky. You have more creative control and more artistic options. And you can get a better surface. But there are times when pouring on site is the only option. For example, Cheng pours on site when he is creating a wall that becomes a cantilevered countertop in one monolith pour.

Pre-casting means seams. Contractors use a variety of materials to fill them: from silicon caulk, to grout, to marine epoxy. Something most contractors agree on, however, is that seams don’t have to be a negative. If they can’t be placed inconspicuously, they work well if they play into the overall design of the countertop.