Bituminous Flashings - Page 6

	BITUMINOUS FLASHINGS

8.11.2 Safety is of primary importance and it is the contractor’s responsibility to ensure that all relevant safety precautions are adhered to. (See section 7B.17). Never heat weld to an area where the flame or heat can be pulled in. Never heat weld directly to a combustible surface or to an area that cannot be seen. If there is a question as to the safety of the area being heat welded then the heat should be applied to the flashing material away from the area of application. When the flashing material is ready for application press into place so that the material is firmly and uniformly set.

8.11.3 A fiber glass base sheet is required under the APP and Classic flashing material in all flashing specifications where the material is to be heat welded over wood, plywood, or any other combustible substrates.

8.12 Heat Weld Application

8.12.1 The advantage of heat welded flashings is the speed at which they can be applied and their ability to conform to irregular surfaces. FesCant Plus strips are required at the junction between the roof deck and the vertical surface to be flashed. These cant strips are made of fire retardant material and are suitable for use in heat weld applications. Wood nailers shall be installed at all eaves, and openings in the roof so that roofing plies, edging and gravel stops may be properly secured. When roof insulation is specified, wood nailers shall be of the same thickness.

8.12.2 Flashing strips shall be of sufficient length to extend a minimum of 4" (102 mm) onto the roof surface. When a two ply flashing system is used for maximum protection at vertical surfaces, the individual plies shall be installed separately and the second ply shall extend beyond the first ply by a minimum of 2" (51 mm) at both the top edge and on the roof surface.

8.12.3 The minimum height for flashing is 8" (203 mm) above the surface of the roof membrane. All flashing must be secured at the top edge with appropriate mechanical fasteners, spaced 6" (152 mm) o.c. maximum, or with some other positive means to prevent sliding or sagging. Suitable metal counter flashing shall be provided to cover the top edge of the base flashing by a minimum of 4" (101 mm).

8.12.4 It is crucial that flashing be firmly and uniformly set, without voids and with all edges well sealed. All laps and edges should be rolled with a rounded edge roller and a ¼ " (7 mm) bead of compound should extend beyond the finished lap. Check all laps for adhesion. Lift up any unbonded areas, reheat the area and press down, forcing the bitumen from the lap (a minimum bead ¼" [7 mm]).

8.12.5 Take special care when applying any APP or Classic membrane flashing material in cold weather (below 40°F [4°C]). All rolls must be stored on end and in a heated trailer or building. Only rolls needed for immediate application should be exposed to ambient conditions. Never throw or drop rolls of APP material in cold weather, sudden shocks can cause cracking of the APP coating asphalt.

8.12.6 JM requires that smooth surface APP flashing sheets be coated with an approved JM roof coating such as Topgard Type A, Type B, or Fibrated Aluminum Roof Coating. Hot bitumen is not an acceptable coating.

8.13 Cold Adhesive Application of APP/PAO Modified Bitumen Flashings

8.13.1 Cold adhesive flashing systems are very similar in construction to hot-applied systems. JM has developed an adhesive, MBR Utility Cement, that is compatible with APP modified bitumen products that incorporate mineral release agents. When cured, this adhesive forms a durable, elastomeric and water-tight film. Unlike conventional cut-back mastics, and most other "modified bitumen cold-process adhesives," MBR Utility Cement will not damage the APP blend in the modified bitumen sheet.

8.13.2 TRICOR M FR, TRICOR S, BICOR S and Classic products have a mineral release agent and are acceptable products to be installed in cold adhesive. APP products with a burn off film cannot be installed in cold adhesive.

8.13.3 MBR Utility Cement can be used as an adhesive substitute to reduce the amount of heat welding that must be utilized when applying APP membranes in flashing systems. It can also be used as a general purpose mastic on most modified bitumen flashing details, or to strip-in the laps of modified bitumen base flashing.

8.13.4 MBR Utility Cement is a one component modified bitumen adhesive designed for use with APP modified bitumen flashing products. MBR Utility Cement is a trowel grade adhesive. Its formulation contains low levels of a mild petroleum solvent, which makes it compatible with TRICOR M FR, TRICOR S, BICOR S and Classic products. It is available in both "winter" and "summer" grade. Both formulas contain the same basic ingredients, but the consistency is adjusted to accommodate the weather conditions during application.

8.13.5 APP modified bitumen sheets are heavy. To prevent slippage when installed on a vertical surface, the sheets must be secured with nails or mechanical fasteners. The fasteners should be spaced a maximum of 6" (152 mm) apart.

Note: Do not use conventional cut-back asphalt cements to bond any JM modified bitumen roofing product to any substrate.

8.13.6 The material is ready to use as shipped and is not to be thinned. It can be installed in temperatures between 40°F (4°C) and 100°F (38°C). However, when the temperature is below 50°F (10°C), the adhesive must be stored in a warm area, approximately 70°F (21°C), for 24 hours prior to application. To minimize installation difficulties associated with cold weather applications, use the less viscous winter grade material. Also, completely unroll the modified bitumen sheets and allow them to relax at least 15 minutes prior to installation. Turning light-colored sheets upside down (dark side up) helps accelerate the relaxation process.

8.13.7 For best results, make certain the surface to which the cement will be applied is clean, dry, flat and free of loose material. All masonry surfaces which are to receive MBR Utility Cement must be primed with JM Concrete Primer. The primer must be allowed to dry thoroughly before application of the cement.