Acrylic Roof Restoration Coating System Metal Corrugated Standing Seam R Panel

The Acrylic Roof Restoration Coating System Metal Corrugated Standing Seam R Panel is the Metacrylics system for existing metal roofs with corrugated, standing seam or R-panel profiles. It is published as sheet A-04, titled Metal Acrylic Restoration Coating System, dated 09-25-17.

In the Installation Spec Book the metal section carries system lives of 10 to 30 years. The system is part of the Metacrylics range of metal roof restoration coatings.

The section drawing has an existing metal roof, a primer, and Metacrylics acrylic topcoats. Two primers are drawn as alternatives.

• Option 1: Acrylic Roof and Tile Primer.
• Option 2: Acrylic Black Primer, described on the sheet as a rust inhibitor.

Three notes appear on the sheet. Acrylic surfaces are very slippery when wet, and non-slip surfacing is recommended in high foot traffic areas on sloped surfaces. Field seams are sealed and reinforced either by 3-coursing with Acrylic Gel and polyester fabric or with Acrylic Base and fabric. All rooftop penetrations, drains, scuppers, flashing, skylights and perimeter edge flashing are sealed or reinforced by 3-coursing with Acrylic Gel and polyester fabric.

The Black Primer is a black, water-based acrylic elastomeric rust inhibitor primer. It is a non-volatile, highly adhesive primer for BUR asphalt, tar and gravel, cap sheet, coal tar and metal surfaces, and once fully cured it has no surface tackiness and can be walked or driven on. It is used as a roof or deck rust inhibitor primer and as an asphalt pavement sealer, and it may also be applied to wood, glass and tile.

• Tensile strength: 250 psi, with elongation of 300 percent minimum (ASTM D-412).
• Hardness: Shore A 48 (ASTM D-676).
• Flexibility: passes a 1/8 inch mandrel bend with no cracking or chipping (FTMS 141a, Method 6221).
• Weathering: 1,000 hours of accelerated weathering with no cracking, crazing or dulling (FTMS 141a, Method 6151).
• Erosion: less than 0.1 mils per year, non-chalking (FTMS 141a, Method 6192).
• Weight: 8.5 lbs per gallon. Solids by weight: 32.9 percent.
• VOC: 19.45 grams per liter; hydrocarbons 18.2 grams per liter, in line with the California Air Resources Board Model Rule for Architecture Coatings.
• Viscosity at 77 degrees F: 1900 seconds. Saybolt Furol at 122 degrees F: 265 seconds.

Metal surfaces are cleaned, dry and free of dust, dirt and oily residues. Loose rust is removed and new galvanized metal is wiped with an acidic solution first. The primer goes on at 1 gallon per 100 sq. ft. by either method. Spray work uses a .031 spray tip, and almost any airless sprayer can be used because the primer has the consistency of water; drying takes 4 to 24 hours. For roller work the drying time is 12 to 24 hours. A quarter inch of water poured over the drum prevents skinning. The primer is stirred before use, stored above 40 degrees F, and not thinned.

Its chemical resistance covers 1 percent sodium hydroxide, diesel, 1 percent hydrochloric acid, Stoklard solvent, salt, boric acid and petroleum ether or naphtha with no effect. Gasoline causes some softening and spotting and lubricating oil some spotting.

Acrylic Gel handles the field seam and penetration reinforcement on metal panels. It is a white, gray or clear acrylic elastomeric mastic, rated Class A for fire and wind uplift by UL as a classified product and listed in ICC-ES Report No. 4785. Cool Roof Rating Council test C-1371 gave solar reflectance 0.87 and thermal emittance 0.90.

In 3-coursing a smooth layer of gel is troweled or brushed onto the seam, a layer of fabric is pressed into it, and a second smooth layer covers the fabric, with the gel and fabric overlapping the field area by at least 2 inches. The gel dries in 12 to 24 hours. The area around the work can be masked with tape for a clean line, and a brush run over the wet gel removes applicator lines. The gel cannot be thinned. Peel adhesion on concrete is 6.3 lbs per linear inch, hardness is Shore A 41, and vapor permeability is 0.016 perms at 81 mils dry film.

The topcoat is Extreme Performance Acrylic White, a reflective protective coating used on metal among other surfaces. Elongation at break is 521.12 percent (ASTM D412, Die C). Solar reflectance is 0.90, thermal emittance 0.88 and SRI 114. Metal preparation is specific: loose rust is removed and new galvanized metal is wiped with an acidic solution before coating.

Rolling takes 2 to 3 coats of 1.33 to 1.5 gallons per 100 sq. ft. each, 3 gallons altogether, and each coat dries a full 24 hours. For non-skid, sand can be broadcast gently over the wet white coating, or half a gallon of #30 mesh sand or rubber granules can be mixed into 2.5 gallons of coating and applied with a texture roller or texture gun. Wet acrylic is extremely slippery on sloped surfaces, and a safety rope is used there.