Tech Talk: Metal Roof Rust Damage


In this edition of Tech Talk, American WeatherStar President Brian O’Donnell and Merv Fisher of Capital Coating, Inc. inspect a horizontal seam on a previously-coated metal roof. The seams on this roof were originally waterproofed using fabric, but this can do more harm than good. The job in this video is a 21,500 sq. ft. metal roof in York, PA.

Merv recommends using our Urethane Brush-Grade 522 product for treating horizontal seams rather than using fabric or a butyl tape. This is because fabric or butyl tape is likely to absorb and trap moisture, which creates rust. Urethane Brush-Grade 522 is the better choice for treating the seams because it is specifically formulated with a thick consistency and is a mastic designed to waterproof and protect large gaps and problem areas.

The metal roof had been previously coated about ten years prior. The team at Capital Coating, Inc. began their recoat process by pressure-washing the roof at 5000 psi with a turbo nozzle. Any areas of old coating that were holding moisture or had rust damage had to be removed, and the roof was given time to dry. Next, they began applying the Met-A-Gard+ system. First, Red Oxide Rust Prime 912 was applied to the roof. As stated earlier, Urethane Brush-Grade 522 was then used to waterproof all the seams and details. Next, a base coat of High-Tensile Acrylic 211 was applied. Finally, an additional layer of High-Tensile Acrylic 211 was applied as the top coat.

Check out our post Preparing a Roof That Has Been Previously Coated for more info on the necessary steps prior to installing a recoat.

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