Met-A-Gard+

Met-A-Gard+ is the high-tensile acrylic metal roof restoration system from American WeatherStar. It is a commercial roof coating system for commercial roof restoration on metal roofs, and metal is the only listed substrate. The system uses High-Tensile Acrylic 211 for both the base coat and the top coat, with a flashing-grade mastic at seams and details.

It is designed for metal roofs with moderate levels of rust and corrosion and with positive drainage. Roofs with areas of ponding water must be corrected before the system is installed. The system is formulated to seal, waterproof and preserve metal roofs exposed to sun, wind and rain, and to deal with freeze-thaw damage in northern climate conditions. It comes in standard, extended and custom color tints, and is used for custom-tint projects.

1. Metal roof substrate, cleaned by pressure washing to remove dirt, dust and debris.
2. Red Oxide Rust Prime 912, applied as step 1A where required.
3. High-Tensile Acrylic 211 base coat.
4. High-Tensile Acrylic 211 top coat.
5. Flashing-grade mastic on all seams and flashing details, and a waterproofing mastic on seams and fasteners.

The base coat keeps mil thickness uniform through the system and bonds to the metal. The top coat forms a flexible membrane. Terms of 12, 15 and 20 years are marked on the system graphic.

High-Tensile Acrylic 211 is a high-solids acrylic elastomeric with high tensile strength and elongation. It contains a mildewcide and algaecides. Its values in the metal guideline and data sheet:

• Solids by volume: 55 percent plus or minus 2
• Elongation: 600 percent plus or minus 50
• Tensile strength: 500 plus or minus 50 psi (ASTM D2370)
• Viscosity: 4,500 cps; data sheet 110 plus or minus 10 KU
• Weight: 11.2 lbs per gallon plus or minus 0.2
• Hardness: 50 to 55, Shore A (ASTM D-2240)
• Permeability: 14 plus or minus 3; water absorption rate 6 to 20 percent
• Initial solar reflectance: 87 percent; emissivity 0.90
• VOC: below 50 g/liter
• Dry time: 2 to 12 hours; shelf life 12 months
• Service temperature: -40 to 200 degrees F

Standard colors are white, gray and tan; other tints and custom colors are available. The material is packaged in 5 gallon and 55 gallon sizes and cleans up with water. It is thixotropic, so it builds evenly on rough, textured or vertical surfaces without pin-holing or sagging.

• Urethane Brush-Grade 522. A single-component urethane flashing material, silver in color, with viscosity of 30,000 to 40,000 cps, 69 percent plus or minus 2 volume solids, elongation of 350 percent plus or minus 50 and tensile strength of 975 plus or minus 25 psi. It is a thick, high-solids, moisture-cure polyurethane applied by heavy brush as received, thinned if needed by up to 6 percent by volume with xylene. It cures in about 24 hours at 60 degrees F and 40 percent relative humidity.
• Polyester fabric. A spunbound, 100 percent polyester fabric with tensile strength of 35 psi, elongation of 100 percent, 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 a second layer of coating goes over the top.

Red Oxide Rust Prime 912 is a red water-based acrylic primer that adheres to rusted and unstable metal and inhibits oxidizing of the substrate. It is 40 percent plus or minus 1 solids by volume with viscosity of 600 to 800 cps, dries in 2 to 3 hours and weighs 10 lbs per gallon plus or minus 0.2. It is applied by airless spray with a 1/2 gpm unit and a #017 tip, by synthetic bristle brush or by short nap roller.

The guideline recommends EcoCleaner 925 for the pressure wash, which is a minimum of 3,000 psi. EcoCleaner 925 is a clear cleaner at 0 g/liter VOC, diluted 5:1 and applied at 1 gallon per 150 square feet. A roto-spray tip speeds up cleaning of metal panels. Acrylic Skylight Sealer 230 seals and reconditions skylights, at 1/2 to 1 gallon per 100 square feet; it does not repair cracked skylights, which need replacement.

• New galvanized metal is allowed to cure at least 90 days, or is treated with a surface conditioner approved by American WeatherStar.
• The roof, including the underside of panels where possible, is inspected for rust. Hidden rust between panels or on the underside cannot be mitigated by a coating system.
• Non-functional equipment and debris are removed from the roof.
• Coatings that are delaminating, and waste products such as oil, oil-based roof cements, solvents, grease and animal fats, are removed.
• HVAC condensate drains are routed to roof drains or plumbed off the roof.
• An adhesion test of the High-Tensile Acrylic 211 base coat is recommended.

Pre-inspection covers HVAC flashing, drainage, water leakage, fasteners, skylights, horizontal and vertical seams, penetrations, sign or display anchorage, and coping and flashing.

The acrylic is applied with ambient and surface temperatures of at least 50 degrees F, with temperatures rising during application. Maximum ambient is 110 degrees F and maximum surface 130 degrees F. It is not applied when the dew point is within 5 degrees F of ambient, when precipitation, fog or dew is imminent before cure, or when freezing is expected before cure.

Metal panels qualify for an NDL (no dollar limit) warranty when attached with gasketed threaded fasteners installed directly into metal purlins. Attachment into wood, or with nails or non-approved fastening methods, is not eligible for NDL coverage. A material warranty alone applies to non-approved methods that American WeatherStar Technical Services has expressly accepted. American WeatherStar warrants that supplied material meets or exceeds published properties, and the contractor guarantees workmanship. A Pre-Project Inspection Report is submitted and approved before work starts, and each job is approved by American WeatherStar first.

Met-A-Gard+ is one of the acrylic systems used in metal roof restoration.