Can I Coat Metal Roofs?
How Do I Coat Metal Roofs?
Coating metal roofs using the AcryShield Roof Maintenance System, ARM, is relatively easy. But first, it is vitally important that the roof be evaluated for the type of metal and original coating used (if any).
If the roof is not coated, it is important to know the metal type. If the roof is galvanized steel, aluminum, or Galvalume, the roof can easily be coated after a thorough pressure wash, rinse and drying. Weathering of these metals causes a tough "scale" to develop on the surface which actually increases the adhesion of the coating to the metal. Two coats of AcryShield roof coating are then applied. AcryShield A500 or A510 is recommended for colder climates, while A400 is recommended for warmer more temperate climates. (See Metal Roof Membranes for more information.)
If the roof is steel and there is no "red rust" (iron oxide), then the roof can be coated as above. However, if there is "red rust" present, this must be removed with a wire brush or wire wheel fitted to an electric drill. After the rust is removed and wiped clean, RustShield A120 primer is immediately applied. The RustShield primer contains a unique additive that prevents "flash rusting", discoloration of the coating due to the fresh steel's chemical reaction with the waterborne coating.
If the metal had been previously coated, the roof is first cleaned as in the uncoated metal coating procedure above, and then coated with the AcryShield coatings.One key distinction: If the coating is Kynar or other PVDF coating chemistry, then AcryShield A130 normally recommended for coating PVC roofing is applied at 0.5 gallons/ SQ. This acts as a primer to provide adequate adhesion of the AcryShield topcoat to the underlying coated metal.
Details Seams and Penetrations:
After cleaning, details such as fasteners, penetrations, lap seams and standing seams are made watertight using butyl caps (applied to exposed fasteners) and butyl tape applied to lap and standing seams. As an alternative, AcryFlex A150/151 and polyester mesh T272 can be applied to seams.
For additional information on metal roofing, download our FREE Metal Roofing Brochure and check out some of our Metal Roof Case Histories – U.S. Coast Guard Hangar at LAX, Hundley Hardware Co., GateGourmet, and Sears Warehouse.