Preventing and Removing Mildew on Exterior Siding

Mildew on siding can be an unsightly and persistent problem for homeowners. This fungal growth detracts from your home’s appearance and can lead to long-term damage if left untreated.

Mildew thrives in damp, shaded areas with poor air circulation. These conditions create the perfect environment for mildew spores to settle and multiply on your home’s exterior. Consistent maintenance and preventive measures are key to keeping mildew at bay.

• Clean your siding annually with a mild detergent solution.
• Inspect your siding regularly for signs of mildew growth.
• Ensure your gutters are clean and functioning correctly.
• Trim trees and shrubs away from your home.

Knowing your siding type can help you choose the most effective cleaning method and preventive measures. To remove mildew from your siding, you’ll need the following items:

• Bucket
• Drop cloths to protect plants and landscaping
• Garden sprayer or pressure washer
• Ladder (if necessary)
• Soft-bristled brush or sponge

Select a cleaning solution. While many homeowners turn to chlorine bleach, there are better alternatives. Chlorine evaporates too quickly to get to the fungi’s roots, creates environmental pollution, corrodes metal fasteners, discolors or damages certain types of siding, and harms nearby plants and grass.

Oxygen bleach is a highly effective and environmentally friendly method for removing mildew from siding, as it penetrates porous surfaces and prevents regrowth. It’s safe for use around plants and on most siding materials.

There are other effective cleaning solutions you can consider:

• Commercial mildew removers
• Trisodium phosphate and water
• White vinegar and water

Properly apply the cleaning solution with a garden sprayer or pressure washer, allowing it to sit on the surface for 10-15 minutes to penetrate and break down mildew effectively. After the solution has had time to work, scrub and rinse, taking care to remove all the cleaning solution, inadequate rinsing can lead to a buildup of cleaning solution, which may attract additional mildew and dirt.

To eliminate the problem of recurrent mildew, consider materials that are naturally resistant to mold growth. Hardie siding resists moisture intrusion and mold growth. Some siding products can be treated with mold-resistant coatings for added protection.