"So far, we haven't seen any lifting or delaminating," Klima says. He'll wait six months before re-flooring the rest of the house. If it doesn't work, Klima says, he'll move to a vinyl composition tile.
In spite of all his trials, says Klima, "I still like my concrete floors. They're currently a multi-colored taupe-brown -- with several large, darker, amoeba-shaped patches that were created by an impossible color match during the second skim coating. Sometimes visitors think that our floor effect was intentional, and that they look good."
Efflorescence isn't the only problem among mid-century modern homeowners who want concrete floors; cracks are another challenge, especially in earthquake country, where shifting and settling can fracture the seamless surface.
Concrete, like all other materials, will slightly change in volume when it dries out. In typical concrete this change amounts to about 1/16 of an inch. Quillen says that although all concrete cracks over time, there are materials on the market that professionals use to help bridge the gaps before a decorative coating is applied. "I've received no complaints so far, but you can't guarantee that it will not reoccur," Quillen says.
For most, the pros of concrete floors outweigh the cons, and the experience of living with concrete underfoot is nothing less than enjoyable.
When Rachel Jordan moved into her Eichler home in San Mateo, the floors were covered with wall-to-wall carpeting. "The single-pane windows created so much condensation in the winter that the water flowed into the carpets, which developed black spots by all of the windows," Jordan says.
Jordan decided on concrete floors for three reasons: she wanted a streamlined, modern look; the carpeting covered up the radiant-heat system so that it was not effectively warm up the house; and since she was considering to take on future remodeling projects, concrete would be easier to match afterwards.
"This was the main reason we decided against tile," Jordan explains. "We did not want to have to re-do the floors after spending so much on them in the first place."
Jordan acquired three estimates before choosing her installer, who soon discovered that the original nine-inch vinyl tile under the carpeting was adhered with asbestos mastic. Jordan then hired an abatement professional to remove all of the old flooring and mastic and followed with testing. Her installer also recommended that Jordan have her floors prepped before he came in to apply a topcoat with the actual design. The result was a medium-gray, glossy floor with a slight marbling effect.
"I think the whole project cost us $15,000," Jordan says, and she likes that her floors are now relatively low maintenance. To keep up the glossy look, polishing every four months was recommended. "The floors look okay when they're not waxed, but they really look great after we wax them. We get them done about once a year," she adds.
Photos: David Toerge; and courtesy Westcoat Specialty Coatings Systems, John Klima
• Beauty: Homeowners love their concrete floors for their personality. Some owners opt for aesthetic simplicity, while others take advantage of the broad choice of colors and textures available.
• Energy efficiency: Concrete floors can help you save energy. They feel cooler in the summer, so there is less of a need to use air conditioning. During the winter, concrete floors absorb the heat from the sun, helping to keep your home warm. For those with radiant-heated floors, concrete is the best flooring surface to maximize heat conduction and minimize energy usage.
• Sustainability: Using concrete floors helps to minimize waste, unlike other types of flooring, such as carpet, which creates waste from padding and carpet scraps. Also, concrete does not contain the harmful VOCs (volatile organic compounds) that many synthetic carpets do.
• Safety: While many smooth flooring surfaces can be slippery, especially when wet, you can add an invisible additive to concrete coatings to provide more traction to the surface.
• Durability: If they are properly installed and maintained, concrete floors rarely need replacement.
• Practicality: Maintenance is simple. Just vacuum or sweep and follow up with a damp mop.