Both interior and exterior brick should be prepped before painting. If you’re painting your brick fireplace, for example, remove all items from around the work area, such as fireplace screens and tools, and mask any area that you don’t want paint on using painter’s tape. Place drop cloths on the floor and secure them in place using painter’s tape. Clean interior brick with water, mild detergent and a scrub brush. Let the wall dry completely before painting.
Outside, remove all window screens, light fixtures, plumbing outlets, electrical covers, shutters and address numbers/placards or cover them with painter's tape before you begin. Use drop cloths to cover cars, patio furniture, shrubs and anything else you don't want to splatter with paint. It's a good idea to cover the ground so you don't get paint on walkways and on the grass. Also, be considerate of your neighbors’ properties while painting.
When using a ladder to reach high areas, invest in an adjustable ladder stabilizer that attaches to the ladder and braces against the roof.
Remove dirt, debris and mildew with water from a garden hose or by pressure washing with water and a mild detergent. Using a pressure washer is the most effective method of cleaning because of its ability to blow dirt and debris out of the tiny crevices and pores in brick. Note: Use a low setting when pressure washing so as not to etch or otherwise damage the brick.
For stubborn mildew, use a bleach-and-water solution when washing the wall. Let everything dry completely before moving on.
Look for any substantial cracks in the surface. Small, hairline cracks can be painted over, but anything larger needs to be repaired before painting. Use a paintable acrylic latex caulk rated for outdoor use to fill cracks. Let the caulk set and dry before painting.
Use muriatic acid to get rid of efflorescence — salt deposits that can form on brick surfaces. Follow the manufacturer’s instructions on how to prepare the acid and water solution. Wet the wall with water from a garden hose before applying the muriatic acid to the wall and scrubbing with a stiff brush. Allow the acid to work into the brick for approximately 10 to 15 minutes and then rinse the surface with water.
Muriatic acid is highly corrosive and can be harmful to your skin. Wear protective clothing, safety goggles and protective gloves when working with muriatic acid.