Flashings, Transitions, & Terminations
M60 RubrPoly Flashing Membranes
Metal Counterflashings & Cap Flashings
On certain prefabricated roof hatches, skylight systems, and rooftop equipment, a relatively short, built in metal counterflashing flange may be provided making it necessary to attach an additional sheet metal counterflashing skirt. The sheet metal skirt shall be installed to extend the premanufactured counterflashing so as to ensure adequate overlap of the flashing membranes, thus restricting wind driven rain and snow from penetrating the roof system. Since metals generally have a high coefficient of expansion, metal flashings shall be isolated from the BUR membrane so as to minimize metal movement from fatiguing or splitting the BUR membrane. Metal flanges are prohibited from being embedded or sandwiched into the reinforcing membrane.
Walls that require flashing membranes shall have metal counterflashings installed in or on the wall above the flashings. The design of this counterflashing shall consist of a separate reglet and counterflashing allowing installation of the sheet metal counterflashing after the flashing membrane is installed. Refer to the "Roof Flashing Details" index. Single piece counterflashings are prohibited. Sheet metal is prohibited from being installed as a flashing embedded into asphalt or the BUR membrane where differential movement may result in fatiguing, cracking, or splitting the roof system membrane.
When precast concrete walls are installed, the designer shall specify the flashing requirements for interfacing the BUR membrane with the precast wall units. Cast-in raggles, often mistakenly called reglets, are prohibited. Design attention shall be given to camber, creep, and the independent thermal movement of the precast concrete walls, the BUR membrane, and the flashing system.
Metal cap flashings or copings are often installed to cover the top of a wall in lieu of masonry copings. Refer to the "Roof Flashing Details" index. For intermediate height parapet walls, metal counterflashings shall be attached to the inside face of metal cap flashings.
Metal gravel stops shall be raised above the waterline or surface of the roof by installing tapered wood blocking. The flange of a metal gravel stop shall be placed over the completed BUR membrane and shall be fastened a minimum of 3" on center to the perimeter of the wood nailer. The gravel stop metal flanges shall be adhered within the flashing membrane sheets. Refer to the "Flashing Details".
Pipe projections through the roof system require metal flashing collars or pipe flashing boots. Metal flashing flanges shall be installed with M60 RubrPoly. Refer to the "Flashing Details".
Overlapped metal joints are required to be sealed from water intrusion with M60 RubrPoly and M300 RubrMastic installed in a three-layer application.
Metal installed as flashings shall be mechanically fastened, and adhered in M300 RubrMastic. In addition, some types of metal seams may be joined with solder or by welding.
Roof System Membrane Protection
Foot traffic can be detrimental to a roof system, especially during extreme temperatures, and therefore must be controlled. Traffic pads or walkways shall be installed in areas that will receive regular maintenance traffic. Pads and walkways shall not be mechanically fastened to or through the roof membrane. All sharp edges shall be eliminated from metal walkways. Asphalt composition walkways are prohibited. Walk pads shall be spaced no closer than 6" from adjacent pads. Walk pads shall not block water run off drainage.
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