To paint concrete successfully—so that it looks good and lasts a long time—proper preparation is of paramount importance. If you follow the steps below, you can achieve satisfying results no matter what concrete you choose to paint, be it the garage floor, basement wall, outdoor patio, or any other part of your property.
MATERIALS AND TOOLS
- Concrete filler
- Power sander with fine-grit disks
- Pole sander
- Trisodium phosphate or other alkaline cleaner
- Metal-bristled brush
- Paving paint or porch-and-floor enamel
- Paintbrush or roller
- Putty knife
- Protective gear (rubber gloves, dust mask, glasses)
When you set out to paint concrete, the process begins rather unglamorously with concrete filler. Use the patch compound to fill in all holes, scratches, and gouges in the concrete. After allowing sufficient dry time, sand the repaired areas until they are smooth.
Using a solution of trisodium phosphate (TSP) and warm water, clean the surface thoroughly, removing all the oil and grease that would otherwise discolor the paint job. Work the solution into the concrete with a metal-bristled brush. To determine the proper ratio of TSP to water, read the package instructions, but figure on about one-quarter cup TSP to one gallon warm water. TSP can harm skin and eyes if it makes contact, so be sure to wear full protective gear.
As the TSP reacts with the concrete, you are likely to notice a slight bubbling across the surface. Let that bubbling continue for about 20 minutes, then hose off the concrete, completely washing away the TSP. Let the surface dry for two days. Afterward, run your hand over the concrete; it should feel like 120-grit sandpaper.
Sweep the area or wipe it down with a dry cloth, depending on the orientation of the surface. Now you’re ready to start painting. Use a paintbrush to apply an initial coat of paving paint (or porch-and-floor enamel) over the perimeter of the area. A regular medium-size paintbrush enables you to achieve good coverage in the corners and along the edges.
Next, use a paint roller to fill in the sections that you didn’t coat with the brush. If you’re painting a floor, remember to start on the far side of the room, so you end up finishing near a doorway or another convenient stepping-off point. In other words, don’t paint yourself into a corner! Let that first coat dry for at least 16 hours or so.
Putty knife in hand, scrape away any protruding lumps or bumps that appeared after the first coat dried. Sand any areas where the paint failed to adhere; if you do end up sanding again, don’t forget to sweep again too.
Apply the second coat in the same way that you applied the first. This time around, however, press down firmly with the roller, mashing the paint into the holes the first coat didn’t penetrate. Before considering the project complete, let the second coat dry for about five days, particularly if the painted surface is a heavily trafficked floor.