Painting Over Masonry Paints

Spray on degreaser and scrub with a stiff-bristled brush. Apply the degreaser to any locations that are soiled with grease or grime. Wash off the degreaser with a water hose.

Allow the water to completely dry on from the masonry paint prior to proceeding. Add deglosser -- found at most paint stores -- to an electric paint sprayer and spray on two coats of deglosser, allowing one hour drying time between coats.

Sandblast the surface of the masonry paint with a portable sandblaster. These sandblasters can be rented from most tool rental stores. Place a plastic tarp below the masonry paint prior to sandblasting to capture the sand and debris. Hold the nozzle 24 to 36 inches from the paint. Do not remove the paint. Only scuff the surface to improve new paint adhesion.

Wash off the masonry paint to remove the sand and dust from the surface. Allow the surface to fully dry before proceeding.

Spray on water-based primer that doubles as a bonding agent. This type of primer can be found at most paint stores. Add the primer to an electric sprayer and spray on three coats, allowing 30 minutes drying time between coats.

Apply three coats of exterior water-based masonry paint over the primer. If the paint is too thick for the electric sprayer, add 1/2 cup of water to the paint to loosen it up. Allow 30 minutes drying time between coats. When spraying the paint on, spray from top to bottom to prevent over-spray of previously coated paint.