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SBS Modified
Bitumen
Specifications |
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Specification
3CIG/3FIG/3PIG |
Three Ply Hot Mopped Modified
Bitumen Gravel Surfaced Roofing
System. For use over JM insulation,
approved decks, or other approved
insulations on inclines up to 3" per foot
(250 mm/m).
For Regions 1, 2 and 3 |
General
This specification is for use over any type of approved structural deck
which is not nailable and which provides a suitable surface to receive
the roof. Poured and pre-cast concrete decks require priming with
JM Concrete Primer prior to application of hot asphalt.
This specification is also for use over JM roof insulations, or other
approved roof insulations which are not nailable and which provide a
suitable surface to receive the roof. Specific written approval is
required for any roof insulation that is not supplied by JM. Insulation
should 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 directly over gypsum, either poured or pre-cast, or
lightweight, insulating 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: 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
On roof decks with slopes up to 1/2" per foot (41.6 mm/m), the
roofing felts and modified bitumen sheets may be installed either
perpendicular or parallel to the roof incline.
Roll an 18" (457 mm) wide piece of one of the intermediate felts
listed into a full mopping of asphalt. Over that, apply a full width piece.
The remaining felts are to be applied full width, overlapping the
preceding felts by 19" (483 mm), so that at least 2 plies of felt cover
the substrate at all locations. Apply a full width piece of one of the cap
sheets listed into a full mopping of asphalt. Subsequent sheets are to
be applied in the same manner, with 4" (102 mm) side and end laps
over the preceding sheets (6" [152 mm] end laps for DynaLastic
products).
Apply all felts so that they are firmly and uniformly set, without voids,
into the hot asphalt. Asphalt temperature should be at the
Equiviscous Temperature (EVT), ±25°F (±14°C), at the point of
application. All felt edges shall be well sealed. The asphalt shall be
applied just before the felt, at a nominal rate of 23 lbs. per square
(1.1 kg/m2). When applying over insulations, more than 23 lbs. per
square (1.1 kg/m2) of asphalt may be needed due to the absorbency
of the insulation. For modified bitumen sheets, the asphalt
temperature shall be at a minimum of 400°F (204°C), or at the EVT,
whichever is higher, when the sheet is set into it. This higher
temperature maximizes the bonding of the modified bitumen sheet.
Cap sheets with polyester reinforcement must be allowed to
relax in an unrolled position prior to installation.
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For cold weather application techniques, refer to Paragraph 7A.31.
Steep Slope Requirements
Special procedures are required on inclines over 1/2" per foot (41.6
mm/m). Refer to Paragraph 7A.29.
Surfacing
Flood the surface with the appropriate asphalt, depending on the roof
slope, at an approximate rate of 60 lbs. per square (2.9 kg/m2).
Embed an acceptable gravel at the rate of approximately 400 lbs. per
square (19.5 kg/m2), or an acceptable slag at a rate of approximately
300 lbs. per square (14.6 kg/m2), into the hot asphalt. Aggregate
must be installed so that there is complete coverage across the
entire surface and at least 50% of the aggregate is solidly adhered in
the hot asphalt.
Asphalt
Asphalt should meet the requirements of ASTM D 312.JM
Guarantees require the use of Trumbull asphalt or another JM
Approved Asphalt. The Contractor must provide an Asphalt
Confirmation Number (ACN) on projects which require a JM
Guarantee. The ACN will indicate that the asphalt was registered with
the approved asphalt source.
For an identical copy of this specification, ask for RS-4199.
