Color Concrete countertops offer unlimited colors for clients. From bright hues to dark rich translucent tones concrete makes a statement.

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The Secrets of Concrete Countertops

Mum's the word
Concrete countertop manufacturers — pour-in-place and pre-cast alike — obtain their materials from standard sources, such as concrete suppliers, ready-mix producers and stucco suppliers. Exactly what goes into the individual mixes, however, is not shared information.

For most contractors there was a good deal of painstaking experimentation before the “ideal” concrete countertop mix design was achieved. With such an intense learning curve, one can easily forgive the hesitancy to share. “You don't get to practice much,” says Pettigrew. “Once we got the basics down, then we began refining it.” Pettigrew generally has a ready mix plant prepare his concrete according to his specifications, but, if the job is a small one, he'll mix the batch himself right on the site. His topping mud is also a secret. “It's my ‘secret sauce,'” he says.

Additives might include polymers and plasticizers. Ralston sticks with half-inch angular rock aggregate and pours as stiff a mix as he can.

Shape is limited only by the designer's imagination and the crafter's knowledge of materials

For reinforcement, more than one material is often used. Zumpfe says he uses fiberglass in his mix for strength and to reduce shrinkage. In the form he often uses vinyl-coated wire shelving, which he places upside-down, or welded wire. Ralston uses stealth fiber mesh (like little strings) and fibrillated fiber mesh (like netting). Sometimes, around sinks for drainage or next to stovetops as hot pot rests, contractors will partially embed metal bars — stainless steel, brass or bronze.

You could say every concrete countertop is made from custom-made concrete and you wouldn't be wrong. Smith observes, “Everyone uses different things and most [contractors/manufacturers] keep their method under wraps.”

My lips are sealed
No less important than any other step is the sealer. “The sealer sustains the countertop, makes it still great looking in five to 10 years. That's what separates the men from the boys,” admonishes Smith, who's firm uses a water-based, USDA-approved sealer that is absorbed into the pores of the concrete. “It doesn't leave a [visible] coating, so the surface looks and feels like stone,” she explains.

Texture and Finish No two countertops are alike. It is the selected finish that will either enhance or disguise authentic details in the concrete.

Ralston says different sealers give you different looks. “Acrylic waxes have a matted appearance. Silicon-impregnated sealers look natural. Polyurethane epoxies have a high gloss.” Which sealer he uses depends on what the client wants.

In kitchen situations, a sealer that is compatible with food use is desirable. Tim Sherry, northeast regional sales manager for Increte Systems, says Increte's Counter Kote is an FDA-approved epoxy, designed to go on thick. He says Increte's Dura-gloss, also FDA-approved and originally designed for use on floors, is a thinner water-based epoxy that also works well on countertops. Bomanite's Florthane is an FDA-approved, highly chemical-resistant urethane sealer. Chris Stewart, Bomanite's director of technical services, says Florthane is available in water-borne and solvent-borne formulas. Seal Hard, by L&M Construction Chemicals in Omaha, Nebraska, is a USDA-approved hardener/densifier. Stu Wood, chemist at L&M, explains that Seal Hard penetrates the surface of the concrete and, through a chemical ion-exchange, bonds with the concrete, plugging up pores and crevices.

The secret is out!
Concrete countertops are popping up everywhere, in residences, restaurants and commercial businesses. While the materials are inexpensive, concrete countertops are cost-competitive with high-end solid surface products and some natural stone products, such as granite, because of all the skill and labor that goes into creating them — figure $65 to $125 per square foot.

“For someone who wanted to get into making them, experimentation is the first step, but you have to know what you're doing,” cautions Girard. “It's too easy to make a concrete countertop — it's difficult to make a good one. Durability depends on who makes them. The more experienced the fabricator, the better.”

The well-known durability of concrete notwithstanding, concrete countertops can crack and be damaged. Dropping a cast iron pot may cause chipping or break an edge. However such an event is likely to damage other countertop materials, as well. Heat, abrasives, sharp knives, the strong colors and acid or base properties of foods are all a concern, but more for the sealer than the concrete itself.

As Smith observes, with repairs “you'll never completely match 101 percent, it may be slightly different, but you're not dealing with something that needs to be computer-matched.” Variations in coloration and embedded objects help hide stains. Zumpfe points out if you use a high-build epoxy resin sealer, scratches and wear marks can be sanded and recoated. Or, as with other classic materials — good leather, wood or natural stone — imperfections add character.

“One of the most challenging things about working on a concrete countertop is that it's like working on a piece of furniture,” Ralston reflects. “Everything is brought up to your focal point and it's constantly under scrutiny. You almost need an artisan to do this work.” Indeed. That appears to be the biggest secret of all.