Met-A-Sil

Met-A-Sil is the silicone metal roof restoration system in the American WeatherStar range. It is a commercial roof coating system for commercial roof restoration, and metal is its only listed substrate. The finish is Silicone 410, with High-Solids Silicone 412 as the optional alternative, applied over a cleaned, optionally primed metal roof.

The system is designed for metal roofs with moderate levels of rust and corrosion and with positive drainage. It is used to coat an entire roof, to make spot repairs, or to add protection at flashings.

1. Metal roof substrate, pressure washed to remove dirt, dust and debris.
2. Red Oxide Rust Prime 912, applied in some cases as step 1A.
3. Waterproofing mastic on all seams, fasteners and flashing details.
4. Base coat of Silicone 410 or High-Solids Silicone 412.
5. Top coat of Silicone 410 or High-Solids Silicone 412, in bright white.

An adhesion test of the silicone base coat on the metal substrate is recommended. Pre-inspection before application covers HVAC flashing, drainage, water leakage, fasteners, skylights, horizontal and vertical seams, roof penetrations, sign or display anchorage, and coping and flashing.

Silicone 410 is a ready-to-use, high-solids, single-component, solvent-borne, moisture-cure silicone. In the guideline it is a UV resistant elastomeric with these values:

• Solids by volume: 69 percent plus or minus 2 (ASTM D-2697)
• Initial elongation: 318 percent; tensile strength 500 psi (ASTM D-412)
• Viscosity: 6,000 plus or minus 1,000 cps
• Reflectivity: 84 percent (C-1549); emissivity 0.85 (C-1371); SRI 105
• VOC: below 250 g/liter
• Flash point: 106 degrees F (ASTM D-93)
• Hardness: 50 plus or minus 5, Shore A
• Water absorption: 2 percent
• Drying time: 1 to 4 hours; minimum application temperature 40 degrees F
• Service range: -40 to 350 degrees F
• Clean up: mineral spirits; shelf life 24 months

Colors are white, gray and tan, in 5 gallon and 50 gallon packaging. The coating is mixed by hand, because it is combustible and an electric mixer is not used.

High-Solids Silicone 412 is a ready-to-use, single-component, moisture-cure silicone at 92 percent plus or minus 2 solids by volume (ASTM D-2697). It is the standard liquid silicone specification for spray polyurethane foam roofing and single-ply restoration, and it is the optional finish in Met-A-Sil. Other published values:

• Emissivity: initial 0.89 (C-1371)
• Reflectivity: initial 0.87 (C-1549)
• VOC: below 50 g/liter
• Flash point: 290 degrees F (COC, ASTM D-92)
• Hardness: 50 plus or minus 5, Shore A
• Drying time: 1 to 4 hours; shelf life 24 months
• Service range: -40 to 350 degrees F
• Clean up: mineral spirits

Standard colors are white, gray and tan, in 5 gallon and 50 gallon packaging.

Several materials are named for seams, flashings and reinforcement:

• Silicone Brush-Grade 422. A single-component, moisture-cure silicone mastic for penetrations, curbs, seams and flashings, white, with 96 percent plus or minus 3 volume solids, elongation above 243 percent at 73 degrees F, tensile strength 289 psi, 4.2 perms and a dry time of 2 to 8 hours. It is packed in 5 gallon and 2 gallon sizes.
• Urethane Brush-Grade 522. A single-component urethane flashing material, silver, with viscosity of 30,000 to 40,000 cps, elongation of 350 percent plus or minus 50 and tensile strength of 975 plus or minus 25 psi. It is applied with a heavy brush and may be thinned up to 6 percent by volume with xylene.
• Non-woven polyester fabric. A 100 percent polyester, hydraulically entangled fabric with 100 percent elongation, 35 psi tensile strength, 22 mils bulk, 11 lbs per square and widths of 36, 20, 12, 6, 4 and 2 inches. It is laid into wet coating and covered with another layer.

Red Oxide Rust Prime 912 is a red water-based acrylic primer that inhibits rust on metal and bonds to rusted and unstable metal. It is 40 percent solids by volume, with 600 to 800 cps viscosity and a 2 to 3 hour dry time, sprayed with a 1/2 gpm unit and a #017 tip.

EcoCleaner 925 is a clear, low-foaming cleaner at 0 g/liter VOC. It is diluted 5:1, applied with a low-pressure sprayer at 1 gallon per 150 square feet, and followed by power washing at a minimum of 3,000 psi. Acrylic Skylight Sealer 230, a translucent coating at 45 percent plus or minus 2 volume solids, seals and reconditions skylights, at 1/2 to 1 gallon per 100 square feet.

• Pressure washing at 3000 to 4000 psi is recommended, and existing coatings are checked for adhesion.
• Silicone is applied by spray, brush or roller as received, without thinning.
• Subsequent silicone coats go on within 24 hours of the prior coat.
• Application is not recommended below 40 degrees F, or if rain is expected within 1 hour. Lower temperatures extend cure time.

For an NDL (no dollar limit) warranty on metal panels, the panels must be attached with gasketed threaded fasteners installed directly into metal purlins. Attachment into wood substrates, or with nails or non-approved fastening methods, is not eligible for NDL coverage. Material warranty only applies to non-approved fastening methods that American WeatherStar Technical Services has expressly accepted. American WeatherStar warrants that supplied material meets or exceeds published properties, the contractor guarantees workmanship, and a Pre-Project Inspection Report is submitted and approved before the job starts.

Met-A-Sil belongs to the silicone roof coating group of systems applied to metal.