in twice the normal amount of roofing sheets and asphalt at the crown].
Extend base sheets approximately 50 mm (2 inches) above the top of cant
strips at vertical surfaces and to the top of cant strips elsewhere. Trim
base sheet to a neat fit around vent pipes, roof drains, and other
projections through the roof. Application shall be free of ridges,
wrinkles, and buckles.
3.3.6
Modified Bitumen Membrane Application
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NOTE: On slopes up to 1:6 (2 inches per foot),
specify membrane application perpendicular to slope
of roof. On slopes greater than or equal to 1:6 (2
inches per foot), specify membrane application
parallel to roof slope.
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Ensure proper sheet alignment prior to installation. [Apply membrane
layers perpendicular to slope of roof in shingle fashion to shed water,
including application on areas of tapered insulation that change slope
direction.][Apply membrane layers parallel to slope of roof.] Bucking or
backwater laps are prohibited. Fully adhere membrane sheets to underlying
substrate materials. Provide minimum 75 mm (3 inch) side laps and minimum
150 mm (6 inch) end laps and as otherwise required by membrane
manufacturer. Stagger end laps minimum one meter (36 inches). Offset side
laps between membrane layers a minimum of 300 mm (12 inches). Offset end
laps between membrane layers a minimum of one meter (36 inches). All
membrane layers shall be installed the same workday, unless supported
otherwise by roof membrane manufacturer application instructions and
approved by the Contracting Officer. Provide tight smooth laminations of
each membrane layer without wrinkles, ridges, buckles, kinks, fishmouths,
or voids. Ensure full membrane adhesion and full lap seals. Rework to
seal any open laps prior to application of subsequent membrane layers. The
completed membrane application shall be free of surface abrasions, air
pockets, blisters, ridges, wrinkles, buckles, kinks, fishmouths, voids, or
open seams.
3.3.6.1
Cap Sheet Installation
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NOTE: Include the option of hot asphalt or torch
application of cap sheet where permissible. Torch
applied cap sheet can be applied over hot mopped
membrane plies. Torch application of cap sheet may
reduce instances of cap sheet blistering.
Where finished appearance of the roof is of
consequence, include the bracketed requirement for
granule application in areas of bitumen bleed out.
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Underlying applied membrane shall be inspected and repaired free of damage,
holes, puncture, gouges, abrasions, and any other defects, and free of
moisture, loose materials, debris, sediments, dust, and any other
conditions required by the membrane manufacturer prior to cap sheet
installation. Do not apply cap sheet if rain or frozen precipitation has
occurred within the previous 24 hours. Align cap membrane and apply by the
specified method with the proper side and end lap widths. [Cap sheet may
be set in hot asphalt or torch applied as recommended by the modified
SECTION 07550
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