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APP Modified Bitumen Specifications |
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7B.12.11 Nailable and Lightweight Concrete Decks: On decks with a slope over 1/2 " per foot (41.6 mm/m), the roofing felts must be installed
parallel to the incline. Nail the end laps of the modified bitumen cap sheet across the width of the sheet on 8 1/2 " (216 mm) centers. All nails
are to be covered by the lap of the next sheet. For slopes from 1/2 " to 2" per foot (41.6 to 167 mm/m), a full-length sheet can be used. For
slopes from 2" to 3" per foot (167 to 250 mm/m), a half-length sheet should be used.
7B.13 Phase Construction
7B.13.1 One of the greatest hazards of roof construction is the application of a roofing system in "phases", where a partially completed roof
system is left exposed to the weather overnight or longer. This can lead to entrapped moisture which can cause premature failure of the
membrane.
7B.13.2 When the installation of the cap sheet is delayed for any reason, the following procedures should be followed:
A. |
Prior to the application of the modified bitumen cap sheet, the surface of the membrane must be examined thoroughly for the presence of
any moisture. If moisture is present, the application of the cap sheet is not to proceed until the moisture has been removed or evaporated
and the surface is dry. |
B. |
The surface of the membrane must be properly cleaned and primed if contaminated by dirt, dust, or debris. The primer must be
completely dry prior to installation of the modified bitumen cap sheet. |
7B.13.3 Under no circumstances shall the installation of the modified bitumen cap sheet be delayed more than 5 days after
completion of the intermediate plies of the roofing system.
7B.13.4 Only multiple felt (two felts with modified cap sheet) should be considered for the delay in application of the modified bitumen cap
sheet. Single ply felt or base felt systems must receive the modified bitumen cap sheet on the same day.
7B.14 Cold Weather Application
7B.14.1 APP and PAO modified bitumens require special application techniques when they are being installed in cold weather. The following
precautions shall be taken when the ambient temperature drops below 50°F (10°C), and are mandatory below 40°F (4°C):
A. |
Modified bitumen products shall be kept warm, or warmed prior to installation. Store these materials indoors or in heated storage
units or warming boxes. If these facilities are not available, placing the materials in direct sunlight may help. Make certain that
modified bitumen rolls are stored on end only; do not store rolls on their side. |
B. |
When the conditions are extreme (below 40°F [4°C]), the rolls must be heated or completely unwound and allowed to warm on the
roof for 15 to 20 minutes. This shall be done with the darker side of the sheet up. The sheet may then be installed using conventional
application techniques. |
C. |
When the ambient temperature is below 40°F (4°C), extra care must be used when handling and storing APP and PAO modified
products. During cold weather, these modified bitumen products must be stored on end in a heated trailer or building, and only the
rolls needed for immediate application should be outside. Materials must be kept dry. Never throw or drop rolls of modified bitumen
products during cold weather. Sudden shocks can cause cracking of the asphalt. DO NOT DOUBLE STACK (with or without
pallets). For heat-weld applied products, heat the substrate prior to rolling the molten modified bitumen into place. Special attention
should be given to the lap area so proper adhesion can be obtained. |
7B.15 Temporary Roof Coverings
7B.15.1 At times, an owner or general contractor may require the building to be closed in at a time when the weather is not conducive to good
roof construction, or the roof area may have to be used as a work platform during construction. Historically, this situation has led to phase
construction, which has resulted in premature roof failure.
7B.15.2 When the complete roof cannot be installed in one operation, the following procedures are recommended:
A. Nailable Decks:
1. Apply one layer of an approved JM base felt, lapping the felt 2" (51 mm), and nailing 9" (229 mm) o.c. along the lap and 12"
(305 mm) o.c. through the center of the sheet. (Sheathing paper should first be installed on wood board decks.)
