DO-IT-YOURSELF : Car Throws a Wrench Into the Painting of Concrete Floors

At first glance, painting a garage floor--or any concrete floor--may seem simple enough. You just scrub the floor as best you can, buy a few gallons of enamel porch paint and roll it on.

Although this is exactly the way it’s been done for years, the results have often been disappointing.

And new Environmental Protection Agency limits on paint solvents have not been a big help. These limits have driven some of the most rugged paints from the marketplace.

Environmentally friendly, water-based epoxy enamels do work reasonably well when applied to concrete floors in basements or in workshops. And they are well worth considering for these areas if you want a pigmented surface.

But when automobiles enter the picture, the slab in your garage becomes a different beast than the concrete floor in your basement. Vehicles have a tendency to leak fluids, and, on hot summer days, they often arrive with sizzling hot tires.

The first problem is that no conventional paint will stand up to oil, gasoline, brake fluid, transmission fluid or any of the petroleum-based lubricants needed to keep a car on the road. A few drops on a painted floor will cause the paint to blister, and once blistered, no amount of cursing or coaxing will make a second coat adhere any better.

The second problem is that conventional paints are thermo-plastic, which means they soften with heat. Park a hot vehicle with hot tires on this paint, and the paint will soften, in some cases enough to stick to the tires. Each time you back away, a patch of paint can go with you, leaving an unsightly blotch.

To avoid this problem, you need a paint that is thermo-setting--in other words, it cures with heat. These specialty paints have been used at the commercial level for years and work well when applied properly.

The problem with thermo-setting paints is that they really aren’t made for homeowners. They are generally two-part epoxies, which must be mixed on-site and applied very quickly, often in less than 30 minutes. Also, because of their high volatility, they require plenty of ventilation, protective clothing and a respirator.

As it turns out, no matter how good the paint, surface preparation is critical. As such, most sources recommend sandblasting or acid-washing a concrete floor before painting.

With sandblasting and two coats of paint, a typical garage floor job could easily cost more than $500.