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APP Modified
Bitumen
Specifications |
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Specification
3CBS-W/3PBS-W |
Three Ply Heat Welded, Base Sheet
Fastened Modified Bitumen Smooth
Surfaced Roofing System. For use
overJohns Manville (JM) insulation,
approved substrate or other approved
insulations on inclines up to 6" per foot
(500 mm/m).
For Regions 1, 2 and 3 |

General
This specification is for use over any type of approved structural deck
with insulation or approved substrate which is suitable to receive a
mechanical fastener and which provides an acceptable surface to
receive the roof.
Specific written approval is required for any roof insulation that is not
supplied by JM. Insulation shall be installed in accordance with the
appropriate JM Insulation Specification detailed in the JM
Commercial/Industrial Roofing Systems Manual. This specification
can also be used in certain reroofing situations. Refer to the
"Reroofing" section of the JM Commercial/Industrial Roofing
Systems Manual. This specification is not to be used over gypsum,
either poured or pre-cast, or lightweightinsulating concrete decks or
fills.
Design and installation of the deck and/or roof substrate must
result in the roof draining freely, to outlets numerous enough
and so located as to remove water promptly and completely.
Areas where water ponds for more than 24 hours are
unacceptable and will not be eligible for a JM Roofing System
Guarantee.
Note: This specification is also for use with JM PAO (Classic)
products. All general instructions contained in the current JM
Commercial/Industrial Roofing Systems Manual shall be considered
part of this specification.
Flashings
Flashing details can be found in the "Bituminous Flashings" section
of the JM Commercial/Industrial Roofing Systems Manual.
Application
Using one of the base plies listed, mechanically fasten with an
approved JM insulation fastener and plate a 26 1/4" (665 mm) wide
piece of base ply through the insulation. The remaining base plies
are to be applied full width with 3" (76 mm) side and 4" (102 mm) end
laps over the preceding sheets. Fasten the laps at 9" (229 mm)
centers, and down the longitudinal center of each felt ply, place two
rows of fasteners, with the rows spaced approximately 11" (279 mm)
apart, and fasteners staggered on approxi-mately 18" (457 mm)
centers. Use fasteners appropriate to the insulation and deck. For
additional fastener information, refer to the fastener data in the "Roof
Decks" section of the current JM Commercial/Industrial Roofing
Systems Manual.

Over the fastened base ply, heat weld a 19 3/4" (500 mm) piece of
one of the intermediate plies listed with 4" (102 mm) side and 6"
(152 mm) end laps. The remaining plies are to be applied full width,
in the same manner, with 4" (102 mm) side and 6" (152 mm) end
laps over the preceding sheet.
Heat weld a full width piece of one of the cap sheets listed so that it is
firmly and uniformly set. Subsequent sheets are to be applied in the
same manner, with 4" (102 mm) side and 6" (152 mm) end laps over
the preceding sheets. All laps must be rolled with a 3" (76 mm)
rounded edge roller. A 1/8" to 3/8" (3 mm to 10 mm) bleedout of APP
compound shall be visible at the edge of all seams. All laps must be
checked for good adhesion.
Application of JM APP/PAO Modified Bitumen Products may
require the use of an open flame propane torch. Improper use
of these materials and application equipment can result in
severe burns, and/or other physical injury, as well as damage
to property. In order to prevent these situations the mechanic
must install the materials using the techniques recommended
by JM and those found in "A Guide to Safety: Torch-On
Modified Bitumens" available from the Asphalt Roofing
Manufacturers Association. These techniques have been
endorsed by the National Roofing Contractors Association
and the United Union of Roofers, Waterproofers and Allied
Workers.
For special precautions for heat weld application of JM Classic
(PAO) products, refer to Paragraph 7B.6.6.
For cold weather application techniques, refer to Paragraph 7B.14.
Steep Slope Requirements
Special procedures are required on inclines over 2 1/2" per foot (208
mm/m). Refer to Paragraph 7B.12.
Surfacing
Smooth surfaced membranes must be coated with a JM approved
coating. The coating chosen will depend on aesthetics and any fire
rating or Code approval required.
Note: When using metric and English sized sheets in the same
system, care must be taken to avoid lap over lap configurations.
For an identical copy of this specification, ask for RS-4350.