Oil paints are typically recommended for concrete painting projects. This is because latex paints have lots of moisture in them that must dry slowly for the paint to adhere properly. Since concrete is very absorbent, it usually drains the moisture out of latex paint too quickly, and such a paint job will quickly begin to peel and crack. If you would prefer to use latex paint on your next concrete painting project, you can still make it work. You just need to make sure that you saturate the concrete well before painting so that it won't feel the need to drink all the water out of your paint.
Buy any supplies that you don't already have on hand. When selecting a paint, look for latex paints such as floor enamel or garage floor paint that have been specially formulated for use on concrete surfaces. If you don't have a wire brush, be sure to get one with very stiff, strong bristles.
Use the wire brush to scrub the concrete surface, if necessary. Surfaces with sections that are slightly crumbling, have been previously painted or are very dirty should be scrubbed as clean and smooth as possible.
Dampen the entire concrete surface. If the surface is outdoors and can be reached with a garden hose, you can complete this job quickly and easily. Otherwise, you will have to use a plastic spray bottle to spray down interior walls very thoroughly. For interior concrete floors, you can spread out a thin layer of clean water with a mop.
Shake the can of paint, open it with the paint can opener and stir the contents with a stirring stick while you're waiting for the water to absorb into the concrete.
Wait for the concrete to become only slightly damp. Make sure there are no pools of water anywhere on the surface. When the concrete gets to this point, it's time to paint. Use a paintbrush to apply a thin, even layer to the entire concrete surface within the next two hours. The moisture from the water will keep the concrete saturated, preventing it from sucking the moisture out of the paint.
Paint a second thin, even layer after the first coat has completely dried. There is no need to dampen the surface again once the first coat has finished drying.