Don't let a cracked or stained concrete patio, porch, path or garage slab drive you to a sledgehammer. If the prospect of pulling out and replacing concrete doesn't appeal to you, put down the sledge and pick up a paintbrush.

An easy and cost-effective way to deal with an unattractive concrete surface is to paint it. Paint will not only conceal cracks, rust and grease stains, but will do wonders for the appearance of the concrete and provide added protection from the elements.

As with any painting project, preparation is important. Part of the preparation involves selecting the right paint for the job. The choices: latex, oil, and epoxy. Of the three epoxy is the most expensive and the least appropriate for most do-it-yourself projects. Epoxy floor paints are typically designed to be used where a special condition exists like on the damp floor of a basement which is being finished out or on a slab that is subject to extensive vehicular traffic.

Alkyd or oil floor paint has a high sheen and, of the three, adheres the poorest to concrete. Like epoxy, it is more costly than the latex floor paint and cleanup requires mineral spirits rather than water.

Our choice for concrete is a latex floor paint. It has the best adhesion properties, is the most flexible, resists hydrostatic pressure and is the most user-friendly during application and cleanup. The latex floor paint that dries to a matte finish is the least expensive, ranging from about $25 to $30 per gallon. A gallon should cover between 250 and 400 square feet.

Before applying the first drop of paint, the concrete must be clean and free of dirt, grease and oil. Start by washing the area with a solution consisting of a cup of powdered laundry detergent in a gallon of hot water. Work the solution into soiled areas with a nylon brush and thoroughly rinse with clean water.

Concrete floors with a smooth finish should be slightly etched in order to make the paint adhere properly. Skip this step if the concrete is already rough or porous. To etch, make a 10 percent solution of muriatic acid. Always add the acid to the water and be sure to wear protective goggles, rubber gloves and rubber boots. Be sure there is plenty of ventilation.

Pour the solution onto the concrete and distribute it with a broom. Allow the solution to stand for about 15 to 20 minutes, until the bubbling ceases, then rinse thoroughly by flushing with clean water. Allow the concrete to dry completely before painting.

Previously painted concrete should be free of all loose, powdery or peeling paint. The surface should be scraped, sanded and washed with the detergent solution described above. Distressed areas or irregularities in the surface should be filled with a vinyl concrete patching compound. In addition, cracks should be opened up with the pointed end of an old-fashioned bottle opener and brushed with a wire brush. Sweep the crack clean and fill it with a vinyl concrete patch. Large gaps should be filled with a siliconized latex concrete caulk. Hairline cracks will not require repair since the paint likely will fill the crack.

After the patches have dried, the paint can be applied. The easiest way to apply the paint is to pour it onto the area to be painted, a section at a time, and rolling it out with a short-nap paint roller designed for use with latex paints. When painting bare or previously unpainted concrete, it's a good idea to apply two coats.

The first coat, which will act as a primer, should be thinned at a ratio of about one pint of clean water to each gallon of paint. For most latex floor paints the second or finish coat can be applied a couple of hours after the first, but it is often best to allow the first coat to dry overnight.

One final note: In painting garage floors and driveways, be aware that plasticizers in synthetic rubber tires may soften and remove latex, alkyd and even epoxy floor paints. While this is not always possible to predict or prevent, it is helpful to allow as much as 20 days curing before permitting tire traffic.