As rainwater and condensation accumulate on vinyl siding, it can develop black spots of mold and mildew. Standard household cleaners won’t necessarily remove mildew from siding, but a solution of bleach or vinegar should do the job. If you use bleach, protect the plants nearby from runoff by covering them with plastic drop cloths. A power washer is the most efficient tool for the job, but not all siding can handle the water pressure, so check with the manufacturer or test a small, inconspicuous area to determine whether you can use a power washer without damage.
- Turn off the electricity to any outlets and lamps on the walls you plan to clean. Cover them with plastic sheeting, and secure the sheeting to the wall with duct tape.
- Mix a solution of 3 parts distilled white vinegar to 7 parts water in a bucket. Alternatively, mix a solution of 1 part household bleach to 4 parts water.
- Dip a long-handled, soft-bristle brush into the solution. Gently scrub any visible mildew spots.
- Pour the solution into a power washer. If you can’t use a power washer on the vinyl without damaging it, use a lower-pressure pump sprayer instead. Spray a 5-foot-wide section of the house with the solution, moving from the ground up to the roof. Avoid angling the spray of the solution upward so it travels under the layers of siding; instead, aim it so it hits the siding from above. Spray from a ladder as you move higher up the wall. Get the siding wet enough for it not to dry while you work.
- Tip the remaining solution out of the sprayer and back into the bucket. Rinse the sprayer quickly and refill it with clean water. Spray the wet strip of vinyl with the water from the top of the house downward to rinse off the solution.
- Repeat the process with the next 5 feet of siding. Continue in this fashion until you have cleaned the entire affected area.
Things You Will Need
- Plastic sheeting
- Duct tape
- Bleach or distilled white vinegar
- Long-handled, soft-bristle brush
- Power washer or pump sprayer
If the siding is dirty as well as mildewy, add 1/3 cup of a mild household cleaner for each gallon of the cleaning solution. If you use bleach rather than vinegar, make sure the household cleaner does not contain ammonia, as ammonia and bleach combine to release a toxic gas.
To save time and effort, consider renting a second power washer or pump sprayer, so you can keep one full of the cleaning solution and the other full of rinse water. If the siding is only mildewy in isolated areas, you might not need to wash the entire surface. Scrub the mildew with the soft-bristle brush and rinse it using a garden hose with a spray nozzle.