How to Clean Roof Mildew

If it rains a lot in your area, you have an overhang of trees above your house or you simply have poor drainage, your home could be subject to ugly green or black roof mildew. If you don't get rid of mildew, it will spread, so it's best to tackle this job as soon as possible.

Things You'll Need

• Extension ladder
• Garden sprayer
• Hose with sprayer nozzle
• Chlorine bleach
• Copper sulfate (if needed)
• Water
• Rubber gloves
• Protective goggles
• Hedge clippers or pruning saw (if needed)
• Tarp or plastic sheeting

Instructions

1. Cover plants near the house with a tarp or plastic sheeting so that the cleaning solution doesn't harm them or soak into their soil. Trim any branches that bump into the roof with hedge clippers or a pruning saw, depending on their size.

2. Fill your garden sprayer with one gallon of water. Then add a third of a gallon of chlorine bleach. Close the nozzle and shake the sprayer to mix up the solution.

3. Pump the sprayer and then spray the cleaning solution onto all parts of the roof that are mildewed. Let it set for 20 minutes to better kill the mildew and help keep it from coming back.

4. Rinse the roof with your garden hose, using the sprayer nozzle. Make sure your get all of the bleach off so that it doesn't hurt your shingles over time.

5. Check to see if all of the mildew is off the roof. If not, repeat steps two through four. If the mildew doesn't come off on the second try, rinse out the sprayer and fill it with a solution of half a cup of copper sulfate to one gallon of water. Let the mildew turn brown before hosing it off.

Tips & Warnings

• If you need to use copper sulfate, you can find it at your local garden center. Look in the fertilizer section. You may need to move the ladder several times to get to all the mildewed areas. It's safer than trying to extend your reach.

• Don't walk on the roof to try to reach the mildew better. The mildew can make it very slippery. If you absolutely have to get on the roof, clean the section you are going to walk on first and let it dry. Never try to clean roof mildew with a power washer. The pressure can be too much for your roof to handle. Since you will be working on the roof, always have a friend assist you. It's not a good idea to climb up your extension ladder without someone holding the bottom. Wear rubber gloves and goggles to protect your eyes and skin.

Resources

• Roof care