Can I Seal Indoor Brick Before I Paint It?

Surface Preparation

• As with other painting projects, you must clean the painting surface before you seal or paint the brick surface. Indoor brick is not subjected to the same amounts of dirt as brick on the outside of a building, but the porous, rough surface of the brick may cause dirt or other debris to cling to it. Wipe buildup off the brick with an old towel or use a vacuum with a brush attachment. If you find any loose pieces of mortar, remove them or secure with mortar before continuing.

Heavy-Duty Cleaning

• A brick fireplace can accumulate heavy amounts of debris, especially soot from smoke and burning wood, some of which hits the brick instead of going up the chimney. The primer you apply before paint can eliminate smaller amounts of soot, but any significant buildup needs to be cleaned off before applying primer. Use mild soap or trisodium phosphate along with water and a scrub brush to remove sooty buildup form the brick. To remove efflorescent deposits, which are white and powdery, from the brick, you only need warm, soapy water and the cleaning brush. Allow the brick to dry completely before applying primer.

Priming

• Brick and mortar can be a thirsty material, soaking up a large amount of paint before the paint dries evenly on the surface. This is why you need to seal brick surfaces before painting. An acrylic primer takes well to brick and mortar surfaces without sinking into the surfaces and requiring multiple coats. You don't need even coverage on brick surfaces, and you can apply the primer the same way you paint brick surfaces.

Painting Process

• Brick presents a different painting process than a flat wall or even a ceiling, since the bricks have channels of mortar between them. Paint manufacturer Behr recommends cutting in the perimeter of the brick surface first, using a paintbrush. Once you've painted a border at least 2 inches wide, paint the brick surface with a paint roller. The roller mostly covers the surface of the bricks, while leaving the mortar largely unpainted. Apply paint to the mortar channels with the tip of your paintbrush to finish the painting process.