How to Pressure Wash Metal Roofs to Remove Mildew

Any type of cleanser rated for interior or exterior mildew removal is sufficient.

Mildew is a result of moisture and shade. A metal roof in a relatively humid climate that is frequently hidden in the shade will develop mold and mildew. Special chemicals can be applied to the roof to help prevent or limit the presence of mildew, but cleaning is the only way to remove mildew. Electric or gas-powered pressure washers with chemical cleansers readily remove the substance from most surfaces, including metal roofs. Using a stiff-bristled broom simplifies the process.

Things You'll Need

• Chemical cleanser
• Pump sprayer
• Stiff-bristled broom
• Pressure washer

Instructions

1. Spray the chemical cleanser onto the surface of the mildew with a pump sprayer. Allow the chemical to absorb for several minutes but do not allow it to dry.

2. Scrub the surface of the roof with a stiff-bristled brush to remove the bulk of the mildew.

3. Spray the roof down with a pressure washer starting from the highest point working toward the lowest edges. Do not spray upward against the roof as you could force water between the seams of the metal roof creating a possibility of mold beneath the roof line.

References

• Ask the Builder: Metal Roofing
• Ask the Builder: Removing Moss and Algae from Roofs