SM-2P-4.5xE — Acrylic-surfaced reinforced roof system

SM-2P-4.5xE is Western Colloid specification SM-2P-4.5xE, revised 03/22, for a fluid-applied reinforced roof system that recovers a smooth surface, cap sheet or single-ply roof. The assembly has two plies of polyester reinforcement and an embedded acrylic surface. It belongs to the Western Cool Roof Systems group and is classed as a commercial roof coating system for commercial roof restoration.

The method is a cold process to upgrade existing roofing, including built-up, modified bitumen, EPDM, TPO and Hypalon. The system is water based with very low odor and is surfaced with a reflective elastomeric coating. The 2P in the code is the two plies, and the 4.5 is the ElastaHyde rate in gallons per 100 square feet.

On low-slope roofs that fall under flat roof waterproofing, it is the heavier of the two ElastaHyde rates within the SM series. A specific specification covers use over EPDM or TPO membranes.

The five layers, with approximate dry weights per 100 square feet, are:

• Base coat of #298 emulsion, 6 gallons, 23 lb.
• Polyester fabric, one ply, 2.5 lb.
• #298 emulsion interply coat at 6 gallons (23 lb).
• Polyester fabric, one ply, 2.5 lb.
• Surface coating of white acrylic ElastaHyde, 4.5 gallons, 32 lb.

Total system dry weight is approximately 83.0 lb and total dry thickness is approximately 143 mils.

The assembly meets UL Class A, Factory Mutual Standard 4470 Class 1, California Title 24, LEED (USGBC) and ENERGY STAR criteria. The referenced publication groups are ASTM, Underwriters Laboratories, Factory Mutual (FM Global), Western Colloid details, drawings and notes, ENERGY STAR guidelines for roof coatings, CRRC, California Title 24 and LEED.

• Polyester fabric is stitchbonded, 2.75 ounce firm or 3.0 ounce soft.
• #850 SWS walkway coating is water based, with acrylic resins, binders and an aggregate that forms a textured non-slip surface.
• #8000 All Weather Elastic Cement is a solvent-based white sealant for wet conditions and for setting metal flanges and sheets.
• #800 Elastic Cement is a water-based acrylic resinous plastic emulsion for terminations, metal joints and drain sumps. It is white or black.
• #970 A2A Bonding Primer, also written #970 AXP, is a clear acrylic primer for adhesion of acrylic coatings to smooth built-up roofing, emulsion and non-granulated modified bitumen. Granulated and fabric-exposed surfaces do not need it.
• #298 Asphalt Emulsion is the base and interply coat. It is an asphaltic bentonite clay emulsion that remains flexible and does not sag, flow or re-emulsify once dry.

The existing membrane is repaired and made sound and watertight, and checked for proper fastening or adhesion. Loose gravel, dirt, dust and debris are removed by vacuum, washing, sweeping or power blower. Light dirt may need only sweeping or blowing, and heavy dirt, dried mud or contamination may need washing.

Valleys and ponding areas are washed, may be primed with #298 diluted 20 to 30 percent with water, and receive an extra polyester ply set in #298 before the membrane.

• Blisters are repaired with a floating patch, or another approved method, using asphalt flashing compound and a modified cap sheet. The blister is cut out with a flat shovel, scraper or knife, and the sheet extends at least 6 inches past the widest point.
• Large splits take the same compound and cap sheet, again extending at least 6 inches. Peel-and-stick modified cap sheet or torch-applied APP can also be used.
• Small splits get a three-course repair with #800: 5 gallons per 100 square feet (about 1/8 inch), an embedded polyester ply, and a second coat.

#298 Asphalt Emulsion has 45 to 50% total solids and weighs 8.2 to 8.7 lb per gallon. Container sizes run from 5 gallon pails to 55 gallon drums, totes and bulk. VOC is zero actual and zero regulatory. Wet film is non-combustible and dry film is self-extinguishing. It shows no cracking or flaking at 32 degrees F and no sag, blistering or slipping at 212 degrees F. It meets ASTM D1227 Type III and D1187 and is the principal component of the Glas-Shield system.

Brush, roller, soft broom or squeegee application is 3 gallons per 100 square feet per coat, with a second coat at right angles. Spray is 3 to 6 gallons. Fabric is broomed into wet emulsion, and a surface coat follows. Firm set takes 12 hours at 70 degrees F and 50% relative humidity.

White ElastaHyde #720 ARC has initial solar reflectance of 84% by ASTM C1549 and initial thermal emittance of 89% by ASTM C1371. SRI is 106, or 93 aged. Wet adhesion to emulsion is above 10 pli and dry adhesion above 17 pli (ASTM D903). Tear resistance is above 100 lbf/in (ASTM D624), water swelling is below 20% (ASTM D471), and fungi resistance shows no growth (ASTM G21). Regulatory VOC is 20 with an actual 10. The CRRC product ID is 0682-003.

The coating is applied by roller, brush or spray, with high-pressure airless spray giving the preferred result, in a two-coat cross-hatch pattern. It is not recommended on surfaces that pond water for more than 72 hours without reinforcement. New emulsion is thoroughly dry before coating, which takes 2 to 3 days in warm, dry weather.