Things You'll Need
Commercial moss remover or bleach
Pressure washer (optional)
Moss prefers a moist and shady environment and has a tendency to form on any area of a home that does not receive direct sunlight. Because moss can penetrate the surface of paint and destroy its protective qualities, all moss must be removed before repainting. If moss is not completely removed prior to painting, the problems associated with moss will be compounded since moss tends to hold moisture on the surface of paint, thereby promoting further growth.
Cover any bushes or flowers growing directly beneath the affected area, using a cloth or tarp.
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Apply a commercial moss-removing agent or diluted bleach to the moss. Commercial agents usually are packaged in a concentrated form. Mix the commercial product with water as per the manufacturer's instructions and pour it into a sprayer. Alternatively, mix bleach with water at a ratio of at least 3-parts water to 1-part bleach (can be as diluted as 10-parts water to 1-part bleach) and pour it into a sprayer. Spray the mixture onto the moss. Use a soft broom to loosen the moss from the surface.
Rinse the treated area with plenty of fresh water and allow it to dry completely. Use a pressure washer or the most forceful setting on the nozzle of your garden hose to remove all traces of the moss and the cleansing agent.
Allow the area to dry completely. Bleach-treated surfaces should be allowed to weather prior to repainting. Paint the dry and weathered surface as usual, following the manufacturer's instructions.
To ensure the wall has weathered enough for repainting, remove the moss in the spring and repaint in the fall.
Bleach may discolor the area. Use it with caution.