How to Apply a Coating to a Flat Metal Roof to Prevent Leaks

Flat metal roofs tend to be more durable that other types of flat roofing. However, by adding a special roof coating to the metal roof, you can further extend the lifetime of your roof and reduce the chance that it might leak. Plan on reapplying the coating to the roof every two-three years for best results. You should also plan on taking a weekend to complete this project to allow for proper drying time between steps.

Step 1: Clean the roof, removing any dirt and grime with a broom.

Step 2: Use a putty knife to remove any flaking paint and make any necessary repairs to flashing and other areas on the metal roof that may need to be repaired. Allow those patches to dry completely before proceeding.

Step 3: Clean the roof with a garden hose to remove any remaining dirt. Scrub away any stains with warm water, dish washing liquid, and a sponge. Let the flat roof dry completely before continuing.

Step 4: Apply metal primer to any areas of the roof where the metal is exposed and looks like it is not in good repair. Let the primer dry completely, then apply a second coat. Let the primer dry once more before proceeding.

Step 5: Cover the heads of screws and nails, as well as the seams of flashing with roof appropriate patching cement. Use a paintbrush to apply it, generously covering areas with a 1 inch perimeter of the patching cement.

TIP: If the roof has already been coated with a metal roofing compound, you may not have to complete this step. Just check to make sure everything is properly covered and touch up areas with the patching cement that you think may be suspect.

Step 6: Mix the metal roof coating, which may have settled after it was manufactured. Pour a bit onto the flat metal roof, then use a long handled paint roller to spread and apply the coating. Be generous when applying the first coat. Allow the coating to dry completely.

Step 7: Apply a second coat, using the same techniques used to apply the first coat.