A brick wall is durable and generally needs little or no maintenance. However, you might need to paint a brick wall if the brick becomes discolored. Sometimes bricks develop unsightly white stains when water interacts with salt in the brick. Painting can cover up these stains.
Step 1 - Prepare the Brick
You may try scrubbing stains on the brick wall with a stiff brush. This doesn’t always work. If the stains don’t go, try muriatic acid. Be very careful with this acid, and wear protective equipment.
Widen any cracks in the bricks. Then blow out the dust and seal with a silicone or acrylic caulk. Wait several hours and apply further caulking if necessary.
If you find mildew on your brick wall, treat it with a solution of household bleach. Allow the solution to penetrate the brick wall for 15 minutes. Then use a scrubbing brush to remove the mildew. Rinse the wall thoroughly and allow it to dry completely.
Step 2 - Prime the Brick
Although priming the brick wall will often help the paint job look better, it’s not always necessary. If your wall contains no problems or defects, you can usually forgo priming.
If you prime, use an exterior latex primer. Often bricks might need a second coat of primer in order to make them match the other areas. Allow the primer to completely dry before you apply paint.
Step 3 - Paint the Brick Wall
For paint, you can choose an acrylic latex exterior house paint. These are available in semigloss, satin or flat finishes.
A better choice for a brick wall is elastomeric paint. This has a high acrylic content; it is rubberized and water-repellent. Because it’s very elastic in composition, it fills cracks in the brickwork. For the paint to be most effective, you should not exceed the spread rate suggested by the manufacturer. Be prepared to apply two coats.
Step 4 - Apply a Finish
You usually don't need to apply a finish over paint on a brick wall. You can, however, choose to apply a finish over the bare brick instead of painting. A film sealer repels water but doesn’t let the brick breathe particularly well.
You can also use a penetrant sealer. These do allow the brick to breathe.
Whichever type of finish you use, the brick wall needs to be completely clean first and free of stains and defects. Allow the bricks to dry completely before you apply any finish.