Silicone Roof Coating System Metal Corrugated Standing Seam R Panel

Silicone Roof Coating System Metal Corrugated Standing Seam R Panel is a Metacrylics system assembly for existing corrugated, standing seam and R-panel metal roofing. It is a silicone coating over metal roofs with silicone finish coats.

The assembly is published as drawing A-04, titled Metal Silicone Restoration Coating System, dated 09-25-17. The drawing shows an existing metal roof with a primer layer under Metacrylics silicone topcoats.

The drawing gives two primer options: Option 1 is Acrylic Roof & Tile Primer, and Option 2 is a 2-part water-based epoxy primer that acts as a rust inhibitor.

The drawing carries three notes. Silicone 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 with Silicone Gel over the seam or with a 3-course of silicone and polyester fabric. Penetrations, drains, scuppers, flashings, skylights and perimeter edge flashing are required to be sealed or reinforced with Silicone Gel or a 3-course of silicone and polyester fabric.

The silicone application book gives the metal systems as 10-, 15- and 20-year systems. Each starts with Acrylic Clear Base at 1 gallon per square (1 SQ = 100 sq. ft.), or Black Primer at the same rate if the metal has rust, with 4 to 12 hours to cure.

• 10-year system: HS Silicone White at 2 gallons per square in one application.
• 15-year system: 2.5 gallons per square in two applications of 1.25 gallons per square.
• 20-year system: 3 gallons per square in two applications of 1.5 gallons per square.

Vertical surfaces may need multiple coats at lower application rates to prevent sagging, with 24 hours to cure between applications.

Before priming, exposed fasteners are tightened or replaced, additional fasteners are added to tighten loose panels, and Silicone Gel is applied over fasteners to encapsulate and seal them.

Open joints, laps and holes are repaired, using a 3-course of High Solids Silicone and polyester fabric where needed. Loose debris and built-up dirt are removed, flaking rust is wire brushed off, and the roof is pressure washed to remove peeling or flaking paint.

For horizontal seams, foot pressure is applied to the underlapping panel next to the joint. If the joint opens more than 1/16 inch, fasteners are added. Bad or buckled field seams and end-laps are 3-coursed with alternating layers of High Solids Silicone and polyester fabric.

For vertical seams that are open more than 1/16 inch, fasteners are added. Buckled vertical seams are 3-coursed in the same way, and the others are filled with Silicone Gel as a lap sealer mastic.

For ridge caps, missing gaskets are replaced and the ridge cap closure cavity is 3-coursed where needed.

The book lists square footage uplift factors for material quantities on metal roofs, to capture extra surface area.

• Standing seam: multiply square feet by 1.3, to capture extra surface area for ribs.
• Corrugated: multiply total square feet by 1.15, for uneven surfaces.
• R-panel: multiply total square feet by 1.12, for uneven surfaces.

For the rooftop items on a metal roof, the book includes gutters, parapet coping, and nosings, edge flashings and gravel stops. Plumbing vents and curbs get Silicone Gel around the penetration a minimum of 3 inches up and 3 inches onto the roof surface, or a 3-course with Acrylic Gel and fabric.

Metacrylics Acrylic Primer (Black) is a black, water-based acrylic elastomeric rust inhibitor primer. It is intended for BUR asphalt, tar and gravel, capsheet, coal tar and metal surfaces, and when fully cured it has no surface tackiness and can be walked or driven on.

Published values: flexibility passes a 1/8 inch mandrel bend without cracking (FTMS 141a, Method 6221); tensile strength 250 psi with 300% minimum elongation (ASTM D-412); hardness Shore A 48 (ASTM D-676); 1,000 hours of accelerated weathering without cracking, crazing or dulling; weight 8.5 lbs/gallon; VOC 19.45 grams/liter; solids content 32.9% by weight; hydrocarbons 18.2 gm/liter.

Chemical resistance includes no effect from diesel, 1% sodium hydroxide, 1% hydrochloric acid and salt, and some softening and spotting from gasoline.

Spray application is at 1 gallon per 100 sq. ft. with a .031 spray tip, with 4 to 24 hours of drying time. Roller application is at the same rate. It is not applied if rain or freezing weather is imminent within 24 hours, or when temperatures are consistently below 40°F.

The coverage rate is 1 gal/100 ft2 (3.78 L/9.29 m2).

Packaging is a 5 gal (18.93 L) pail or a 55 gal (208.2 L) drum.

Elongation is 200% (±15) and tensile strength is 300 psi (±25) by Die C, ASTM D-412.

Hardness measures Shore A 45–55 on the duometer, with a tear strength of 45 lbs/in.

Volatile organic content is 48 g/L (0.40 lbs/gal).

Published reflective values are 88% reflectivity, 91% emissivity and an SRI of 110.

The coating can be sprayed, brushed, rolled or applied with a notched squeegee.

The pump should produce a minimum of 3500 psi at the spray gun head and 3 gallons per minute, with a 5:1 transfer pump feeding it.

The coating is not applied below 40°F (4.4°C) or when precipitation is forecast within 48 hours.

Cure time extends when the coating goes on at temperatures below 40°F (4.4°C).

Spray equipment holding uncured material is flushed with VM&P naphtha or mineral spirits.

Because cure is by reaction with moisture, equipment without moisture lock hoses, fittings and seals can build up cured material on hose walls and unsealed connections.

Solids are 94% (±2) by volume and by weight under ASTM D-2697.

The gel meets ASTM D-6694-01, Standard Specification for Liquid-Applied Silicone Coating used in Spray Polyurethane Foam Roofing.

At 75°F and 50% RH the gel is tack free after more than 3 hours and cured in 24 hours.

ASTM D-412 gives 300 psi tensile strength (Die C) and 200% elongation, with Shore A 45–55 hardness and 45 lbs/in tear strength.

The gel is not applied below 40°F (4.4°C) or when precipitation is forecast within 2 hours.

Storage is dry, cool and above 65°F (18°C), with wood pallets rather than concrete floors.