GR-2P-24-XE — Gravel-roof reinforced restoration system

GR-2P-24-XE is a Western Colloid fluid-applied reinforced roof system specification, revised 10/20, for recovering a gravel or rough surface. Its assembly classification is a two-ply polyester reinforced membrane with an embedded acrylic surface. The specification is filed with the Western Cool Roof Systems series. The manufacturer's specification index lists it as a gravel-surfaced system, 2-ply polyester reinforced membrane with an embedded acrylic surface, using #298 Emulsion and ElastaHyde Acrylic White.

The method is a cold process for upgrading existing gravel roofing. It is water based with very low odor, reinforced with lightweight polyester fabrics, and surfaced with a reflective elastomeric coating. A #298 fill coat precedes the membrane layers. Built-up gravel roofs are among the flat roofing systems it addresses.

The assembly has six numbered layers, with approximate dry weights per 100 square feet.

• 0. Fill coat of #298 emulsion, 12 gallons or as needed, 45 lb.
• 1. Base coat of #298 emulsion, 6 gallons, 23 lb.
• 2. Polyester fabric, one ply, 2.5 lb.
• 3. Interply coat of #298 emulsion, 6 gallons, 23 lb.
• 4. Second ply of polyester fabric set in emulsion, 2.5 lb.
• 5. Reflective surface coating of white acrylic ElastaHyde, 3 gallons, 21 lb.

Total system dry weight is 72.0 lb without fill and 117.0 lb with fill. Approximate total dry thickness is 130 mils without fill and 215 mils with fill.

The assembly meets California Title 24, Factory Mutual Standard 4470 Class 1, LEED (USGBC) and ENERGY STAR criteria. Referenced publications are ASTM, Western Colloid details, drawings and notes, Factory Mutual (FM Global), ENERGY STAR roof coating guidelines, CRRC, California Title 24 and LEED.

The polyester fabrics named in the materials list are Western Colloid's T325 at 2.75 ounce soft and T272 at 3.0 ounce soft, both stitchbonded and used as reinforcement in asphalt emulsion or acrylic coatings.

• WCP-SS, equal to Tietex T325, is a 2.75 to 3.0 ounce stitchbonded fabric with a soft finish. It conforms well to semi-smooth or rough surfaces and works over vacuumed, spudded or filled gravel. Fewer stitches per inch improve wetting and reduce the brooming needed. It comes in 10 square rolls, 40 inches by 324 feet.
• WCP-HS, equal to Tietex T272, is a 3 ounce stitchbonded fabric, a medium-soft style that conforms to smooth or semi-smooth surfaces such as cap sheet, smooth surface and filled or spudded gravel. Its close knit may need light brooming to embed it and remove air pockets. Published properties include a thickness of .025 inch, average tensile of 57 lb, elongation of 61%, burst strength of 176 lb and trapezoid tear of 16 lb. Rolls come in 10 square (40 inches by 324 feet) and in 4, 6, 12 and 18 inch widths, each 300 inches long.

• #850 SWS walkway coating is a water-based acrylic coating with an aggregate for a textured, non-slip walking surface on smooth and coated roofs.
• #8000 All Weather Elastic Cement is a solvent-based white sealant that can replace #800 Elastic Cement when more immediate water resistance is needed.
• #800 Elastic Cement is a water-based acrylic resinous plastic emulsion in white or black, with elongation over 500% and 65 to 70% solids by weight.
• #970 A2A Bonding Primer is a water-based clear acrylic primer that improves adhesion of acrylic coatings to smooth asphalt products.
• #298 Asphalt Emulsion is the fill, base and interply coat. It has 45 to 50% solids, weighs 8.2 to 8.7 lb per gallon, has zero VOC, and meets ASTM D1227 Type III and D1187.

The #298 emulsion is spray applied at 3 to 6 gallons per 100 square feet, or by brush, roller, soft broom or squeegee at 3 gallons per 100 square feet per coat. Up to 10% water may be added for spraying, with the application rate raised by the same percentage. It reaches a firm set in 12 hours at 70 degrees F and 50% relative humidity, shows no cracking or flaking at 32 degrees F, and shows no sag or blistering at 212 degrees F.

White ElastaHyde #720 ARC has initial solar reflectance of 84% (ASTM C1549), initial thermal emittance of 89% (ASTM C1371), SRI of 106, aged SRI of 93, CRRC ID 0682-003 and Class A under UL 790 and ASTM E108. It is applied at 50 to 100 degrees F ambient at 75 to 100 square feet per gallon per coat.

Very rough surfaces and surfaces with embedded gravel receive a #298 fill coat at 10 to 12 gallons per 100 square feet, or as much as the existing gravel surface needs. Spudded gravel may need less. Gravel of 1/4 to 3/8 inch takes 10 gallons of fill, 1/2 inch gravel takes 12 gallons, and larger gravel may take more. The specification sets no maximum amount.

The fill coat must be approved by the manufacturer before the membrane goes on, and work does not proceed until approval is given. Valleys and ponding areas are washed and may be primed with #298 at 20 to 30 percent dilution. They then take an extra polyester ply in #298.

The existing membrane is repaired and made sound and watertight, and its fastening or adhesion is checked. Gravel, dirt and debris that are loose are taken off by vacuum, washing, sweeping or power blower.

• Blisters: removed and repaired by the floating patch method with modified cap sheet in asphalt flashing compound, edges at least 6 inches past the widest point.
• Large splits: the same embedded cap sheet repair, or peel and stick modified cap or APP torch applied sheet.
• Small splits: a three course method with #800 at 5 gallons per 100 square feet (about 1/8 inch), one polyester ply, then 4 gallons per 100 square feet over the fabric.

The system is applied at a minimum of 55 degrees F and rising. Rain, inclement weather or temperatures below 40 degrees F within 48 hours after application rule out application, as does ice or frost on the surface. Preparation and repair work that uses no water-based materials may proceed just before inclement weather.

The membrane starts with #298 Asphalt Emulsion at 6 gallons per 100 square feet over the approved fill. A half-width starter strip of polyester is embedded at the low edge, followed by full-width sheets up the roof. A second coat of #298 at 6 gallons per 100 square feet goes over the first ply, and a full-width second ply is embedded from the low edge. Each ply is lightly broomed for full saturation, with no wrinkles or voids. The polyester ends 2 inches above the cant, the wet fabric is not walked on, and no top coat of #298 goes on the polyester. The membrane cures before coating.

When excess emulsion or a top coat does reach the fabric, #970 A2A primer goes on at one half gallon per 100 square feet after washing off asphaltic residue. Exposed polyester does not need it.

• Base flashing: one ply of 6 inch (or wider) polyester in #298 at 5 gallons per 100 square feet over the cant strip, ending at least 2 inches above the cant and 2 inches onto the deck.
• Wall flashing: one full ply in #298 at 5 gallons per 100 square feet, reaching at least 3 inches onto the deck beyond the base flashing.
• Edge metal: low or no rise replacement edge nailed at 4 inches on center and stripped in with polyester and #800.
• Vent and pipe flanges: set in #8000 with nails; #800 stays off the flange of a new flashing.
• Clamping-type drains: three coats of #800 or #8000 over the sump area, at least 18 inches from the drain center, with the membrane lapping the cement by at least 3 inches.
• Surface treatment: #800 and polyester in a three course method over pipe flashings, cones, exposed metal joints and flanges before the reflective coating.

Drains, scuppers, valleys, waterways and locations where water ponds for more than 48 hours receive an extra polyester ply set in ElastaHyde at 3 gallons per 100 square feet, extending 12 inches past the ponding area. It goes on before the final coats.

ElastaHyde 720 ARC goes over the entire roof in two coats of 1.5 gallons per 100 square feet, the second at a right angle to the first, with 24 hours of drying between them. It is mixed well, strained for spray and not thinned. #850 SWS walkway coating is optional, in two coats of 2 gallons per 100 square feet at least 24 hours apart.

White is the base color of ElastaHyde #720 ARC, with California Tan and Platinum Gray also available. All three are stated to meet California Title 24, and standard and custom colors are offered. It is supplied in 5 gallon pails, 55 gallon drums, totes and bulk tankers. A #720 QS Quick Set version exists for use when damp, wet or rainy weather is expected before the coating dries.