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Concrete Floors, Epoxies
This is a new angle for epoxies. They have been used for years on concrete floors in factories, hotel lobbies and other commercial settings because of their adhesive properties, hardness and resistance to chemicals.
by John Strieder
A plethora of pigments, flakes, powders and additives are available to help epoxy coats suggest everything from the stateliness of marble to the shimmer of a “candy-coated” hot rod.
The pigments on the market radically expand the color palettes of decorative concrete contractors, according to Lee Tizard, vice president of sales for flooring supply company Floric Polytech Inc. “You can change the integral color of the floor to almost any other color you want,” he says.
Decorative epoxies are sold in flats, mattes and high glosses. There are metallics, pearlescents that change color with the light, phosphorescents that glow in the dark, and fluorescents that strike the eye with vivid, glowing colors.
Granitelike flake floors — epoxies saturated with vinyl chips that give a garage floor a rich rocky appearance — have become extremely popular in garages, Tizard says. “Epoxy granite floors are sometimes referred to as poor man’s terrazzo.”
Chameleon glitter, like the kind used in custom-painting cars, can give the floor of a trendy nightclub or restaurant the striking ability to change colors as customers walk across it. From one direction it looks green, and from another, red.
Contractors who sell these special-effects floors are making a killing, Tizard says. “The materials cost might be double, but that still doesn’t warrant the extra $3 per square foot contractors are getting paid. Obviously in time prices will come down. But it’s definitely something that’s very profitable, and it looks good.”
Even so, Manuel says that commercial architects often feel more comfortable experimenting with epoxies than do homebuilders. “Their mind’s eye is a little bit better for seeing what they can expect with an epoxy,” he says. “It’s not the sort of thing you try and see if you like. They are very difficult to remove.”
They’re also hard to apply, especially for contractors for whom sealing a back porch usually means pumping acrylic out of a sprayer.
Epoxy, a coating that cures by chemical reactions, is more temperamental than acrylic paint, a liquid that cures by evaporation.
“Typically with these things you just need a good clean surface,” says Manuel. But by clean, he means pristine, devoid of any powder, oil, acid or compound that could disrupt the curing and bonding process. Often, the surface needs to be roughened, which is best accomplished with shotblasting or grinding.
“Epoxy’s tough to bond,” says Tubbs. “The surface has to be clean. There’s a lot more prep work getting that stuff to stick.”
And epoxies have their limitations. Traditionally, their biggest liability has been their lack of “breathability,” the ability to let moisture vapor seep through them into the open air. When those vapors are trapped under a coating, something has to give, and it’s often the epoxy.
Vapor pressure in concrete is one of the main reasons epoxies fail, says Manuel, noting that most epoxies cannot be applied on green concrete surfaces. Another reason they fail is improper pH levels in the concrete.
Epoxies are also notorious for chalking and yellowing outdoors. But aliphatic epoxies, unlike aromatic epoxies, stand up to the outdoor elements, and offer better gloss retention as a bonus. Vexcon’s PowerCoat Epoxy System does not yellow or chalk even in aromatic form, has better breathability than standard epoxies, and can be applied as soon as the concrete is troweled, Manuel says.
However, nonyellowing epoxies introduced in the 1990s cost three to four times as much as typical epoxies, notes Essig. And epoxies have a tendency to show wear patterns, he adds. “The best epoxy is not going to match the abrasion resistance of a two-component urethane.”
Tubbs, owner of Concrete Graphix, once had to eat a $20,000 job because epoxy he laid on an acid-stained floor came up a year later.
Now, he takes no chances. He sticks to one brand he trusts. If an epoxy manufacturer doesn’t make acid stain, he says, it may not have tested its epoxy on acid stain. “There’s a lot of stuff out there that’s not that good.”
Duarte of Versatile urges contractors to find out if a company that supplies their epoxy employs a chemist and manufactures in-house. “These guys often have no manufacturing capability, no technical service,” he says. “Sometimes the company is just an ex-contractor. That’s the biggest thing we have to fight out there.”
Epoxies should also be tested with a mock-up before they are used on the job, he notes. While epoxies in general are known for properties such as adhesion, strength, and chemical resistance, a given epoxy may not possess all of these traits. “Epoxy coatings are formulated for a wide array of specific end uses,” he says. “You need to know what you’re putting down and understand why you’re doing it.”
Epoxies can also be used in combination with other types of coatings to produce the right blend of properties, Duarte says. “My favorite is using an epoxy flood-coat for high film build and adhesion to a substrate,” he says, “followed by a topcoat of urethane to provide improved chemical, scratch and mar resistance in decorative applications.”
Tizard of Floric Polytech says one of the biggest problems for contractors lurks in the lips of their epoxy cans. When a contractor stirs chemical “B” into can “A,” some of the “A” material can surge up into the lip of the can and not get blended with the rest. After the mix is poured onto the concrete floor, the unblended material in the lip shows up as soft spots in the coating. “That’s universal within the industry, that people make that mistake,” Tizard says.
His solution is simple — mix the epoxy in the source can, pour it into a second and mix again for about 30 seconds, then pour it into a third to carry it to the concrete surface.
Tizard also has several tips for coaxing flashy effects from an epoxy.
For example: When an epoxy with metallic additives is laid on a floor, the pigments can form lines like a mowed lawn. To get a uniform-looking finish, Tizard recommends letting the epoxy cure for about an hour, then spritzing the surface with a dispersal agent such as alcohol or a flow-and-leveling agent. The tiny drops of fluid have a dramatic effect. “Each one is like dropping an atom bomb in a forest,” he says. The resin flows back into the small craters, but the pigments remain displaced.
Another tip: Lay a pigmented base coat down, then throw a coat of a water-based metallic on top. Spray the second coat with a liquid release, like one used for stamp overlays. “It gives a hammered bronze effect, like a hammered bronze sink,” Tizard says.
And one more: Pour different colored epoxies together and blow them with a leaf blower. This will create amazing marbleized effects, Tizard says. Then you can spray a dispersing agent, which could also be pigmented with pearlescents. “We have just started exploring blending this effect with metallic and color shift pigments,” he says. “The variations are unlimited.”
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