Acrylic Roof Restoration Coating System Foam

The Acrylic Roof Restoration Coating System Foam is the Metacrylics system for existing spray polyurethane foam roofs. It is published as sheet A-06, titled Foam Acrylic Restoration Coating System, dated 09-25-17. The Metacrylics Installation Spec Book gives system lives of 10 to 30 years for spray polyurethane foam (SPF) on pages 37 to 40.

The system sits with the Metacrylics acrylic range for low-slope roof assemblies, and it uses the same water-based acrylic family as Metacrylics EPDM, TPO and built-up systems.

The section drawing has an existing foam roof with Metacrylics acrylic topcoats on top. Two alternative layers are drawn between them.

• Option 1: Acrylic Roof and Tile Primer, with two notes on the sheet.
• Option 2: Acrylic Clear Base.

Note 1 requires all rooftop penetrations, drains, scuppers, flashing, skylights and perimeter edge flashing to be sealed or reinforced by 3-coursing with Acrylic Gel and polyester fabric. Note 2 recommends that all existing ponding areas be reinforced with polyester fabric.

Roof and Tile Primer is a clear, water-based acrylic primer that improves the adhesion of elastomeric coatings to existing roof or walking surfaces. It dries clear and not tacky. The film has an elongation at break of 700 percent, a glass transition temperature of 17 degrees C and a water absorption of 5 percent. Its dispersion is anionic with a density of 1.03 at 23 degrees C, solids of 16-20 and pH of 7-8.

Application is by spray or roller at 0.25 to 1 gallon per 100 sq. ft. The spray tip is .031 and barricades are placed around the job. The primer dries in 1 to 4 hours, or enough to walk on, and cold temperatures slow it. Tools are cleaned with water. The product is stored above 40 degrees F, agitated for 2 to 3 minutes before use, and skinned material is removed before re-use.

Extreme Performance Acrylic White is listed for use over foam as well as BUR asphalt, tar and gravel, granulated cap sheet, rolled roofing, metal, concrete, wood, EPDM, TPO, PVC and stucco. The formulation carries about 50 percent more TiO2 and 50 percent more copolymer resin than the standard acrylic white, and its initial elongation is 592.63 percent (ASTM D6083-05e1). It is white, with no zinc oxide.

• Weight: 11.3 lbs per gallon. VOC: 27.5 grams per liter.
• Low temperature flexibility: pass at 1 inch and -40 degrees F (ASTM C836).
• Flash point: none at 200 degrees F.
• Saybolt Furol at 122 degrees F: 265 seconds. Particle charge: negative.
• Not for use with potable water.

A final one-coat application is 1.5 or 2 gallons per 100 sq. ft., depending on the Metacrylics system. Three gallons per 100 sq. ft. are needed to prevent delamination in ponding areas and to maintain performance under UV and freezing conditions.

Gel is the water-based elastomeric mastic used with Stitchbond polyester fabric at foam roof details. It is white, gray or clear. Samples tested for temperature cycling and penetration averaged 1.626 before testing and 1.610 after weathering, a thickness change under 1 percent, and showed no tearing or cracking. Tensile strength is 156 psi with 149 percent average elongation, hardness is Shore A 41, and peel adhesion on concrete is 6.3 lbs per linear inch. The gel is applied in three courses: gel, embedded fabric, and a covering layer of gel, which dries for 12 to 24 hours.

Wind uplift is 105 PSF and fire resistance is Class A under ASTM E-108 and UL 790.