end of the continuous run
is more than half the required interval, an
additional joint shall be
provided. Space joints evenly. Join extruded
aluminum gravel stops and
fascias by expansion and contraction joints
spaced not more than 3600
mm 12 feet apart.
3.1.11
Base Flashing
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NOTE: Bracketed first sentence applies only to
shingled roofs. Do not include for built-up
roofing. Normally, only bituminous base flashing
should be specified with built-up roofing. Limit
use of metal base flashing to locations where
flashing is subject to injury by foot traffic and to
runs of 6000 mm 20 feet or less when used with
built-up roofing. Flashing for heating, plumbing,
and electrical equipment should be specified in the
appropriate sections.
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[Lay the base flashings with each course of the roof covering, shingle
fashion, where practicable, where sloped roofs abut chimneys, curbs, walls,
or other vertical surfaces.] Extend up vertical surfaces of the flashing
not less than 200 mm 8 inches and not less than 100 mm 4 inches under the
roof covering. Where finish wall coverings form a counterflashing, extend
the vertical leg of the flashing up behind the applied wall covering not
less than 150 mm 6 inches. Overlap the flashing strips [or shingles] with
the previously laid flashing not less than 75 mm 3 inches. Fasten the
strips [or shingles] at their upper edge to the deck. Horizontal flashing
at vertical surfaces must extend vertically above the roof surface and
fastened at their upper edge to the deck a minimum of 6 inches o.c. with
[large headed aluminum roofing nails] [hex headed, galvanized shielded
screws] a minimum of 2-inch lap of any surface. Solder end laps and
provide for expansion and contraction. Extend the metal flashing over
crickets at the up-slope side of [chimneys,] [curbs,] [and similar]
vertical surfaces extending through sloping roofs, the metal flashings.
Extend the metal flashings onto the roof covering not less than 115 mm 4.5
inches at the lower side of [dormer walls,] [chimneys,] [and similar]
vertical surfaces extending through the roof decks. Install and fit the
flashings so as to be completely weathertight. Base flashing for interior
and exterior corners shall be factory-fabricated. Metal base flashing
shall not be used on built-up roofing.
3.1.12
Counterflashing
Except where indicated or specified otherwise, insert counterflashing in
reglets located from 230 to 250 mm 9 to 10 inches above roof decks, extend
down vertical surfaces over upturned vertical leg of base flashings not
less than 75 mm 3 inches. Fold the exposed edges of counterflashings 13 mm
1/2 inch. Where stepped counterflashings are required, they may be
installed in short lengths a minimum [8 inch by 8 inch] [8 inch by 10 inch]
or may be of the preformed one-piece type. Provide end laps in
counterflashings not less than 75 mm 3 inches and make it weathertight with
plastic cement.
Do not make lengths of metal counterflashings exceed 3000
mm 10 feet. Form the flashings to the required shapes before installation.
Factory-form the corners not less than 300 mm 12 inches from the angle.
Secure the flashings in the reglets with lead wedges and space not more than
450 mm 18 inches apart; on [chimneys and] [stair/elevator towers] short
runs, place wedges closer together. Fill caulked-type reglets or raked
SECTION 07600
Page 17
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