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Built-Up
Roofing
Specifications |
A. Wet or damaged materials should not be used.
B. Never apply any roofing materials during rain or snow, or to
wet surfaces. Moisture trapped within the roofing system as a
result of this can cause severe damage to the roof membrane
and insulation.
C. Review the guidelines for application of roofing, roof
insulations, coatings and accessories shown in the current
Johns Manville Commercial/ Industrial Roofing Systems
Manual.
D. Always start application at the low edge of the roof per the
individual specification diagram.
E. Good roofing procedure restricts the application of hot
asphalt to a maximum of 6' (1.83 m) in front of the roll.
F. When using mechanical felt laying equipment, be sure that
all orifices are open.
G. All roofing ply felts should be well set into the hot asphalt
utilizing a squeegee or some other device.
H. Take special care when applying coated felts in cold
weather. Roll out and cut all mineral surface BUR felts to
specified lengths and allow them to flatten. Check the
temperature of the asphalt at the mop or asphalt-spreader to
determine that it is at the proper application temperature. Do
not apply mineral surfaced cap sheet when the air temperature
is below 50°F (10°C).
I. Do not mix different grades of asphalt or dilute asphalt with
any material.
J. Heat the asphalt according to the manufacturer’s
recommenda-tions. Check the temperature of the asphalt at the
kettle and at the point of application. Have accurate
thermometers on all roofing kettles. Adhere to the guidelines
for the heating of asphalts in this section of the manual.
K. Always use the proper grade asphalt. A JM Technical
Service Specialist may allow the roofing contractor to deviate
from our published recommendations in warmer climates. A
good guideline to follow regarding the use of asphalt is "Use
the softest grade of asphalt commensurate with the slope and
climatic conditions."
L. Always install water cut-offs at the end of each day’s work
to prevent moisture infiltration into the completed work area.
Water cut-offs should be completely removed prior to resuming
work.
M. Heed the cold weather application procedures in
Paragraph 6.13 of this section.
N. Always install the complete roofing system at one time.
Phased construction may result in slippage of felts due to
excessive amounts of asphalt between the phased plies.
Blisters due to entrapment of moisture, or poor adhesion of the
membrane due to dust and foreign material collecting on the
exposed felts, are other hazards of phased construction.
O. It is essential that traffic be minimized on a freshly laid roof,
while the asphalt is still fluid. Asphaltic displacement through
the porous fiber glass ply felts can result from rooftop traffic
during asphalt "set" time. Depending on specific job factors,
this set time can be as long as 45 minutes. Asphaltic
displacement can result in "phantom" leaks and blistering of
the membrane.
P. Always comply with published safety procedures for
all products being used. See the "Introduction" section
of the current JM Commercial/Industrial Roofing Systems
Manual, MSDS, and container labels for health and safety
recommendations.
6.6 Roofing Felts
6.6.1 JM manufactures different fiber glass roofing felts for a
variety of roofing needs: felts for flashings, vapor retarders, roof
plies, base sheets, and special felts for venting.
6.6.2 Roofing felts are furnished in rolls consisting of one or
more squares. A "factory" square of roofing contains sufficient
material to cover 100 sq. ft. (9.29 m2) of roof surface
accounting for nominal side and end laps.
6.7 Roofing Asphalts
6.7.1 Roofing asphalts are available in four grades, shown in
Paragraph 6.7.8 of this section. In general, they are grade
specified by softening point. The slope of the roof governs the
grade to be used, in conjunction with the climatic constraints.
The success or failure of a roofing system depends on the use
of the proper grade of asphalt as called for in the roofing
specification.
6.7.2 Health and Safety See Section 1.9 for health and safety
information.
6.7.3 Heating Asphalts are susceptible to damage from
overheating. Overheating, even for short periods, can "crack",
or degrade the asphalt (a drop in softening point and slight
oiliness is a symptom). Fall back in softening point can result in
slippage of felts in the roofing system. As the softening point
decreases, the viscosity or "holding power" of the interply
asphalt decreases, resulting in slippage. If the overheating is
more gradual, the asphalt may "age" prematurely, losing the
beneficial light oils that help the roofing system weather and
stay waterproof. Since asphalts are thermoplastic, their
viscosity varies with temperature. Application temperature
must be in the range which will permit an adequate film of
asphalt, whether applied by mop or machine.
6.7.4 The JM Technical Center, in conjunction with the National
Roofing Contractors Association and the Asphalt Roofing
Manufacturing Association, has been involved in considerable
research developing guidelines for the proper heating and
application of hot asphalt. These guidelines use the principle of
Equiviscous Temperature.
6.7.5 In conjunction with these guidelines, the following
information is printed on the cartons of asphalt, or on the bill of
lading for asphalt shipments.
1. The Softening Point as determined by ASTM D
312.
2. The Minimum Flash Point (FP) of the asphalt as
determined by ASTM D 92.
