To ensure protection against water entry into a
newly installed roofing system, the membrane flashings shall be
installed as the application of the primary membrane
The membrane flashing shall be uniformly
supported by and adhered to a solid substrate. Gypsum board
substrate is not accepted and must be covered with new plywood or
OSB sheathing prior to membrane flashing application.
The membrane flashing shall be uniformly
supported by and secured to an acceptable, solid substrate.
Acceptable substrates consist of minimum 12.7mm (1/2”) thick
plywood, minimum 11.1mm (7/16”) oriented strand board,
minimum 6.4mm (1/4”) factory-coated glass faced gypsum roof
board over wood sheathing, dimensional lumber, smooth concrete,
smooth surfaced concrete block or masonry and minimum 22 gauge flat
When preservative treated wood components are
incorporated into a roof assembly, the potential for corrosion of
some metal fasteners, sheet steel and roof decking exists when in
direct contact with non-C.C.A. (Chromate Copper Arsenate)
With adequate support and backing the accepted
substrates for the attachment of the membrane flashing are
dimensional wood blocking, minimum 12.7mm (1/2") thick plywood,
minimum 11mm (7/16") thick oriented strand board, minimum 22 gauge
sheet metal flashing, concrete and smooth surfaced concrete block
The minimum height of the membrane flashing at a
wall, roof penetration, or curb shall be 200mm (8”) above the
primary membrane surface in a conventional design and 200mm
(8”) above the insulation or concrete paver ballast material
in a protected membrane or combination design. The minimum height
of membrane flashing at door sills shall be 100mm (4”) above
the primary membrane surface, or concrete paver surface measured at
the door sill location.
For protected membrane and combination BUR
designs, the vertical membrane flashing termination shall extend a
minimum distance of 200mm (8”) above the primary insulation
when using gravel ballast or 200mm (8”) above the paver
surface when concrete pavers are used as the ballast.
The maximum length of the membrane flashing felt
during application is limited to 3048mm (10 ft).
Modified bitumen flashing plies shall be applied
in roll width sections.
The tops of walls not covered by membrane
flashing shall be covered with a water resistant sheet extending
down from the top of the blocking a minimum distance of 50mm
(2”) on each side.
Inorganic (Fiberglass) roofing felt is not
permitted for use in membrane flashing applications.
At scupper drains, the membrane flashing shall
cover the sheet metal scupper flanges and shall extend past the
scupper opening to terminate inside a minimum distance of 75mm (3")
measured from the interior face of the parapet or wall.
Exposed penetrations through the membrane
flashing shall be placed no lower than 200mm (8”) above the
finished roof surface.
BUR-7.4 Modified Bitumen Membrane
Flashing (See Figure 3)
Two (2) plies of an ARCA Warranty Ltd. accepted
SBS modified bituminous membrane may be substituted for three (3)
plies of No.15 organic felt membrane flashing at horizontal to
When a granular surfaced SBS modified bitumen
cap sheet membrane flashing is specified, the flashing cap sheet
need not be protected by a sheet metal base flashing. Where a sheet
metal base flashing is specified to protect the SBS membrane
flashing, the cap sheet membrane need not be granular
When sheet metal cap flashings protect the top
of walls and parapets, the granular surfaced cap sheet shall
terminate at the top inside face of the detail and need not be
carried across the top of the wood blocking over the base sheet
For cant edge details, both the base and cap
sheet membrane flashing plies shall be fully adhered and extend to
the top of the cant. The cap sheet ply shall be turned down the
fascia and be mechanically fastened to the fascia plate.
For combustible substrates, the base flashing
ply shall be a self-adhering SBS base sheet adhered in a compatible
primer, approved by the membrane manufacturer. Round top nails
shall supplement the adhesion of self-adhering SBS base
For conventional designs, the SBS base ply
membrane shall extend from the toe of the cant over the primary
membrane a minimum horizontal distance of 100mm (4"). The base ply
shall completely cover the sloping cant face and extend vertically
the greater distance of minimum 150mm (6") above the primary
membrane of 50mm (2”) above the top of the cant. Base sheet
side laps shall be minimum 75mm (3”) wide. The base ply shall
be fully adhered to the primary membrane, the cant and the vertical
The SBS cap sheet flashing ply shall completely
cover the base sheet membrane ply and extend horizontally on to the
primary membrane an additional 50mm (2”) past the base sheet
termination. Extend the cap sheet a minimum distance of 200mm
(8”) above the primary membrane. Membrane flashing cap sheet
end laps shall be staggered from the base sheet end laps. The cap
sheet shall be thermally fused (torched) to the SBS base flashing
When using SBS modified bitumen membranes,
the maximum membrane flashing height is restricted to 1067mm (42").
A variance request must be submitted to the Technical Committee
when membrane flashing height is to exceed 1067mm (42").