ISSUE
For a variety of reasons, there are occasions when property owners desire to repaint an existing metal roof.
ANALYSIS
Whether the reason is to obtain a different look or extend the life of an older roof, metal roofing is usually ideal for repainting. The primary criteria is that the roofing can be cleaned down to a clean, dry, non-chalking surface that offers good adhesion for the new paint system. Most quality “name brand” paints offer primer and top coat formulations that are recommended for repainting metal roofing. Additionally, air-dry Kynar/Hylar formulations are available through metal roofing manufacturers but they are costly. It must be understood that field-applied paint systems will not have the same weathering characteristics of factory-applied finishes.
SOLUTION
If, for whatever reason, it is desired to repaint a new metal roof, check with the manufacturer to see if a “primer only” finish is available. If not, then it is recommended to lightly “scuff” the new paint surface with steel wool or a “scotch-bright” pad and wash off any residue before applying a new primer and top coat. Prior to repainting a new or older metal roof product, the surface should be hand-cleaned or power-washed with the following solution: 1/3 cup powdered laundry detergent such as Tide™, 2/3 cup trisodium phosphate such as Soilax™, 1 quart 5% sodium hypochlorite solution such as Clorox™, and 3 quarts of water. Rinse with clear water after cleaning and allow to dry thoroughly before applying primer. Allow primer to dry thoroughly before applying top coat. It is recommended to try a small “test area” and check for good adhesion before proceeding with repainting the entire surface. Adhesion test can be achieved with an 8” piece of duct tape. Firmly apply 5” of the tape to the repainted surface and then quickly tear off the tape by pulling on the remaining 3”. If the repainted surface adheres to the tape, adhesion quality is less than desirable.
