Parge is a thin coat of mortar applied over the top of vertical concrete to fill surface voids, fissures and small holes. It is intended to refine the look of the concrete, prevent outgassing and improve the overall appearance of the surface. If you apply paint directly over bare parge, poor adhesion will inevitably lead to finish failure in the form of chipping. To promote good coverage and long-term durability, condition the parge with a base primer. Use the proper application tools that will promote better coverage without leaving skip marks throughout the finish.
Things You'll Need
Roller extension pole
1 3/4-inch nap roller cover
3-inch nylon paintbrush
1-inch nap roller cover
Exterior acrylic paint
Wash exterior parge, using a pressure washer; dust interior parge with a broom. Let exterior parge dry for at least two hours.
Position canvas dropcloths beneath the parge.
Coat exterior parge with acrylic primer, using a roller. Add latex primer to interior parge. Equip the roller with a 1 3/4-inch nap roller cover. Roll vertically, moving from the left side of the vertical concrete surface to the right side. Touch up the parge, using a nylon paintbrush. Don't use a polyester brush which is better suited for slick surfaces. Let the parge dry for two hours.
Wash the nylon brush and roller three times, using clean tap water.
Paint the parge just as you primed it. Add two coats, waiting two hours between each coat. Use a 1-inch nap cover to prevent runs. Let the finished parge dry for two hours.
Use latex paint on interior parge and an exterior acrylic paint when finishing exterior parge. Don't use latex paint on exterior parge; ultraviolet sunlight will cause the finish to fade.
Be sure to thoroughly clean the parge to prevent tiny dust particles from leading to poor adhesion.