National Coatings Blog

Coating Metal Roofs

Posted by Nicole Gale on Mon, Dec 19, 2011 @ 11:20 AM

Coating metal roofsCoating metal roofs using the AcryShield Roof Maintenance System, ARM (see diagram), 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 A510 (excellent for coating metal roofs) are then applied.  

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, made specifically for coating metal roofs, 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, call us at 800-423-9557 or email info@nationalcoatings.com

Tags: Roof Restoration, Roof Maintenance, Roof Coating, Cool Roof Coating, Coating Metal Roofs, Metal Roofs