Many do-it-yourselfers have difficulty removing paint from relatively sensitive surfaces, which are prone to scarring. Over-aggressive removal techniques often lead to permanent damage to the underlying surface. Fortunately, if you need to remove paint from a concrete foundation, you can embrace aggressive removal methods because the surface is so durable.
Strip as much paint as possible from the concrete foundation using focused water pressure generated by the pressure washer. Wait three to four hours for the foundation to dry.
Scrape remaining paint from the foundation using a metallic putty knife.
Sand remaining stubborn bits of paint from the foundation using a power sander stocked with 80-grit sandpaper. Stop here if the foundation is free from paint.
Apply solvent to a 3-by-3-foot area of the concrete foundation, using a paintbrush specifically intended for use with oil paints.
Wait 60 seconds for the solvent to loosen the paint. Scrape the remaining paint from the area using the putty knife. Use a wire brush to remove paint from awkward, sunken areas within the foundation. Continue until you have stripped the foundation bare.
Do not use the power sander while the foundation is coated with solvent, as the intense friction could start a fire.
Don't smoke while working with flammable solvents.