NDFR-2P-XE — New-construction reinforced roof system

NDFR-2P-XE is a Western Colloid specification for a fluid-applied reinforced roof system. Its assembly classification is new construction over a nailable deck, built with two plies of polyester reinforcement and an embedded acrylic surface. The system belongs to the manufacturer's Western Cool Roof Systems group and is listed as a commercial roof coating system.

The specification, revised 10/20, calls the assembly a cold process method of installing a new roofing membrane. The system is water based and has very low odor. The reinforcement is lightweight polyester fabric, and the surface is a reflective elastomeric acrylic coating.

It is one of several Western Colloid system specifications that share the same component materials. Within that group, the NDFR-2P-XE is the version for a new nailable deck: it starts with glass sheets and an SBS modified base sheet nailed to the deck before any emulsion is applied. For commercial buildings with a low-slope roof waterproofing scope, the water-based membrane and acrylic surface are the defining features of this assembly.

The assembly has seven components, in installation order, with approximate dry weights per 100 square feet.

• Atlas FR-50 coated glass fiber sheet, one ply, 20 lb. Two layers of Atlas FR-10 may replace one FR-50 sheet.
• 25 lb SBS modified glass base sheet, one ply, 25 lb.
• Base coat of #298 asphalt emulsion, 6 gallons, 23 lb.
• Polyester fabric, one ply, 2.5 lb.
• Interply coat of #298 asphalt emulsion, 6 gallons, 23 lb.
• Polyester fabric, one ply, 2.5 lb.
• Surface and reflective coating of ElastaHyde white acrylic, 3 gallons, 21 lb.

Total system dry weight is approximately 117.0 lb per 100 square feet. Total system dry thickness is approximately 210 mils.

The polyester fabric is a 2.75 to 3.0 ounce, firm, stitchbonded polyester used as reinforcement in asphalt emulsion. The Atlas FR-10 and FR-50 sheets are fire-retardant, coated glass fiber mats made by Atlas Roofing Corporation. The base sheet is a minimum 25 lb, SBS asphalt coated, G-2 type fiberglass sheet that conforms to ASTM D 4601-95.

Flashing uses an SBS modified bitumen cap sheet that is at least 4 mm thick, granule surfaced, and reinforced with fiberglass, polyester, or both. Asphalt flashing compound is an asbestos-free, cut-back roof mastic reinforced with non-asbestos fibers, ASTM D 4586-86 Type 1. A modified version of the compound is formed into a permanently rubberized compound.

Other named materials in the assembly:

• #298 Asphalt Emulsion is a clay-stabilized asphalt emulsion, ASTM D 1227 Type III, made in a continuous colloid mill process without added surfactants or additives.
• #800 Elastic Cement is a water-based, highly concentrated acrylic resinous plastic emulsion with inert mineral pigments and fillers, available in white or black.
• #8000 All Weather Elastic Cement is a solvent-based white sealant used on asphalt built-up roofing, modified bitumen, metal and single-ply roofs including EPDM, PVC, TPO and Hypalon.
• #970 A2A Bonding Primer is a clear acrylic primer for adhesion of acrylic coatings to smooth built-up roofing, emulsion and non-granulated modified bitumen. It is not required on granulated or fabric-exposed surfaces.

The surface coat is ElastaHyde #720 ARC, a white, 100% acrylic elastomeric coating that meets ASTM D6083 for acrylic roof coating. Published values for the white coating:

• Initial solar reflectance 84% (ASTM C1549) and initial thermal emittance 89% (ASTM C1371).
• Solar Reflectance Index of 106, and 93 after aging (ASTM E1980-01).
• CRRC rated product ID 0682-003, with initial solar reflectance 0.84 and weathered 0.75, and initial thermal emittance 0.89 and weathered 0.91.
• Dry flammability Class A under UL 790 and ASTM E108.
• Initial elongation above 250% and above 175% after weathering (ASTM D2370); tensile strength above 250 psi.
• Passes 1000 hours of xenon arc UV exposure (ASTM D4798) and shows no fungal growth (ASTM G21).
• Solids of 53% by volume and 66% by weight; weight per gallon approximately 11.5 to 12 lb.

The coating is listed by the Cool Roof Rating Council and can be used to comply with 2016 California Title 24 cool roof requirements. Western Colloid has determined that it meets ENERGY STAR guidelines in white, Platinum Gray and California Tan. The tan and gray versions carry CRRC IDs 0682-005 and 0682-004.

The assembly meets UL Class A, California Title 24, LEED (USGBC) and ENERGY STAR criteria. Publications referenced in the assembly text are ASTM, Underwriters Laboratories, Western Colloid details, drawings and notes, ENERGY STAR guidelines for roof coatings, CRRC, California Building Standards Code Title 24, and LEED.

The deck must have all nails securely fastened, and joints between decking boards may have gaps of no more than 1/4 inch. Wider gaps are caulked with #800 Elastic Cement and allowed to cure. The surface is clean and free of dust and debris.

• The FR-50 glass sheet is installed over the prepared deck and tacked in place.
• The SBS modified base sheet goes over the glass sheet, lapped 2 inches on the sides and 6 inches on the ends. It is nailed on 9 inch centers through the laps and on 18 inch centers along lines 12 inches from each edge.
• Valley and ponding areas receive an extra ply of polyester set in #298 asphalt emulsion before the membrane is applied.
• Base, wall and curb flashings are installed with the modified bitumen cap sheet after the base sheets and before the membrane.
• The base flashing over the cant strip uses one ply of polyester fabric, 6 inches wide or wider, set in #298 emulsion at 5 gallons per 100 square feet.

Metal edge is nailed at 4 inches on center, stripped in with polyester fabric and #800 Elastic Cement, and left with at least 2 inches of bare metal at the edge. Vent and pipe flanges are set in a bed of #8000 All Weather Elastic Cement, nailed, and stripped in with polyester and #800.

The system is water based. Application takes place at a minimum of 55 degrees F and rising. It is not applied when rain, inclement weather or temperatures below 40 degrees F are expected within 48 hours, or when ice or frost is on the roof. Preparation and repair work that uses no water-based materials may proceed just before inclement weather.

#298 emulsion is applied at a minimum of 50 degrees F, at 3 gallons per 100 square feet per coat by brush, roller, soft broom or squeegee, or at 3 to 6 gallons per 100 square feet by spray. Drying time at 70 degrees F and 50% relative humidity is 12 hours to a firm set. ElastaHyde covers 75 to 100 square feet per gallon per coat and is applied between 50 and 100 degrees F ambient, at a minimum dry thickness of 20 mils and a recommended 24 mils or more.