Moisture Control | Roof Decks | Rigid Insulation | Roof Membranes

 

ROOF MEMBRANES

Cants, Curbs, & Nailers
Cants
The bent radius of the horizontal and flashing membrane shall not exceed 45 degrees. Cants shall be installed at angle changes such as those created by roof to wall, roof to curb, or other roof to vertical surface intersections. The installation of cants shall be to lessen the angle of these horizontal to vertical plane changes for the benefit of all reinforcing sheets and membranes.

Curbs
Curbs shall not be installed upon or fastened through roof insulation. All curbs, wood blocking, and penetrations shall be firmly secured to the roof deck before installation of the roof system. Drains and vent pipes shall be secured prior to installation of the roof system so as to prevent damage to the roof system. Rooftop installed equipment shall be mounted on raised curbs.

Nailers
Well secured, preservative pressure treated, and decay resistant wood blocking and nailers shall be installed at all perimeters and penetrations for fastening the flashing reinforcing sheets, and sheet metal counterflashings. Wood nailers shall be installed on all prefabricated curbs and hatches for mechanical attachment of the flashing reinforcing sheets.

Flashings, Transitions, & Terminations
Flashings, transitions, and terminations shall be installed as shown in the flashing details listed in the Roof Flashing Details Index on page 73. Non-asphalt surfaces such as concrete and metal that come in contact with asphalt roof system components shall first be primed with M400 RubrPrime at the uniform rate of 1 gallon per 100 square feet, and the primer shall be allowed to dry prior to further installations.

M60 RubrPoly Flashing Membranes
Flashing membranes shall be constructed from M60 RubrPoly reinforcing sheets. Cut the RubrPoly sheets to size and install in a manner that minimizes the occurrence of voids and wrinkles, taking care that the RubrPoly flashing sheets do not form a bridge where there is a change of direction such as where a wall intersects with the plane of the roof deck. Ensure that the drainage flow is over or parallel to the flashing reinforcing sheet seams in a manner similar to the seams in the field. Apply pressure to the flashing sheet seams so as to make complete adhesion. Flashing sheet seams shall be carefully inspected, and unsealed locations, voids, or raised reinforcing sheet intersections shall be repaired.

Metal Counterflashings & Wall Cap Flashings
Sheet metal counterflashings and wall cap flashings shall be installed so as to cover the top of curbs and to overlap the upper reinforcing sheet edges of flashing reinforcing sheets. On curbs that support equipment being frequently serviced, the counterflashings or wall cap flashings shall extend down over the flashing reinforcing sheets to the base of the cant, terminating near the horizontal roof membrane surface so that the flashing reinforcing sheets are well protected.

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 reinforcing sheets, 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 reinforcing sheets so as to minimize metal movement from fatiguing or splitting the roof system membrane. Metal flanges are prohibited from being embedded or sandwiched into the reinforcing sheets.

Walls that require flashing reinforcing sheets shall have metal counterflashings installed in or on the wall above the flashing reinforcing sheets. The design of this counterflashing shall consist of a separate reglet and counterflashing, allowing installation of the sheet metal counterflashing after the flashing reinforcing sheets are installed. Refer to the flashing details starting with the Roof Flashing Details Index on page 73. Single piece counterflashings are prohibited. Sheet metal flashings are prohibited from being embedded into asphalt or reinforcing sheets, because 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 horizontal membrane reinforcing sheets 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 horizontal roof system membrane, and the flashing roof system membrane.

For non-wall supported roof decks, the flashing reinforcing sheets shall be fastened to a vertical wood upright with the horizontal base attached to the roof deck. Refer to the flashing details for examples of vertical wood blocking. After the flashing reinforcing sheets have been attached to the wood uprights, the metal counterflashings shall be extended down over the flashing reinforcing sheets. This detail allows for independent movement of the wall and metal counterflashings without damage to the reinforcing sheets in the horizontal field, and the flashing reinforcing sheets. Metal cap flashings shall be installed to cover the top of a wall. Refer to the flashing details starting with the Roof Flashing Details Index on page 73. 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 field membrane by installing tapered wood blocking. The flange of a metal gravel stop shall be placed over the completed flashing 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 reinforcing sheets. Refer to the flashing details starting with the Roof Flashing Details Index on page 73.

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 starting with the Roof Flashing Details Index on page 73.

Metal Materials
Make weather secure joints between various metal roofing and flashing metals by cleaning the metals with a solvent dampened rag. Remove dirt, dust, and oils so as to prepare the surfaces to be securely mated.

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 system membrane. All sharp edges shall be eliminated from 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.