How to Apply Metal Roof Cleaner

Cleaning a metal roof thoroughly is important before doing a complete inspection or sealing against leaks. Standard soap and water will not remove mold, mildew, tree sap or any number of forms of residue built up over time. A good cleaning job will require the application of a strong cleaner. Trisodium Phosphate (TSP) works well to clean a metal surface when used sparingly. Mixed with chlorine bleach, it will remove years of dirt and grime as well as mold and mildew.

Things You'll Need

• TSP (trisodium phosphate)
• Water
• Bucket
• Chlorine bleach (if needed)
• Push broom
• Garden hose or power washer

Instructions

1. Mix 1/2 cup of TSP to 2 gallons of water in a large bucket. Mix 1/2 cup of chlorine bleach to the solution if the metal roof has mold or mildew present.

2. Pour a few ounces of the cleaning mixture onto a small section of the roof. Spread it evenly with a long-handled push broom and let it soak for 10 to 15 minutes.

3. Scrub with the broom to loosen any stuck-on dirt or residue. Rinse with a garden hose or power washer set at no higher than 1000 PSI (pounds per square inch). Continue this process across the entire roof.

Tips & Warnings

• The home improvement specialists at naturalhandyman.com advise that the release of trisodium phosphate is harmful to the environment. It is not a cleaner that is safe to use every day. (See reference.)

• To avoid metal discoloration, work in small sections and leave the TSP product on the metal for a period no longer than 20 minutes at a time.

• Use safety glasses and gloves when working with TSP. It is harmful and irritating to eyes and skin.

• Use caution when working on a roof. Maintain awareness of the location of the edge at all times.

Resources

• TSP use