Vinyl siding requires less maintenance than other cladding materials, but it does need some care from time to time. Rainwater and condensation on vinyl siding can cause black mold and mildew to grow. Mold, mildew, and algae can grow on vinyl siding when they feed on sugars from trees, dirt, and dust on the siding.
Household Cleaners
Standard household cleaners may not remove mold, mildew, and algae from vinyl siding. You can remove them by using a solution of bleach or vinegar. If you use bleach to clean your siding, cover nearby plants with plastic drop cloths.
Power Washer
A power washer is most effective, but it cannot be used with all siding. If water gets driven behind the siding at lap joints and corners, it can rot the wood if the house does not have a weather barrier under the siding. This is a concern in older homes because in the past building codes did not require a weather barrier under vinyl siding. The siding was nailed directly onto wood sheathing. Check with the siding’s manufacturer or installer or test the power washer on a small, inconspicuous area to make sure it does not cause damage before you use it on all of the siding.
Before you begin power washing your vinyl siding, turn off the electricity supplying any outdoor outlets or lamps. Cover them with plastic sheeting and duct tape it to the wall. Prepare a solution of either 30 percent distilled white vinegar and 70 percent water or 20 percent household bleach and 80 percent water in a bucket. Dip a long-handled brush with soft bristles in the solution and gently scrub away any mildew.
Pour the rest of the solution into a power washer or a low-pressure pump sprayer. Spray the house in sections five feet wide, starting at the ground and working your way up to the roof. Be careful not to spray upward because the solution could get under the siding. Spray the solution so it falls on the siding from above. Use a ladder to spray high parts of the wall. Wet the siding enough so that it will not dry out as you are working.
Pour the remaining solution back into the bucket. Rinse the sprayer and fill it with clean water. Spray the siding starting at the top of the house and working your way down. Repeat in five-foot sections until you have removed all of the mold and mildew.
Oxygen Bleach
You can also remove mold, mildew, and algae from vinyl siding with oxygen bleach. Mix the powder with warm water, stir until it dissolves, and then spray it generously on the siding. It is best to do this when the siding is in the shade. Let the oxygen bleach solution bubble on the siding for about 10 minutes, scrub the siding with a brush, and rinse it with a hose. It is best to use oxygen bleach solution on dry siding.