3. Nail a full-width (32-inch) strip over the first
strip, using the same nailing schedule.
4. Nail the next full-width strip with the outer edge
14 inches from the outer edges of the first two
strips to obtain a 2-inch overlap over the edge of
the first strip laid. Continue laying full-width
strips with the same exposure (14 inches) until
the opposite edge of the roof is reached. Finish
off with a half-strip along this edge. This
completes the two-ply dry nailer.
5. Start the three-ply hot with one-third of a strip,
covered by two-thirds of a strip, and then by a
full strip, as shown. To obtain a 2-inch overlap
of the outer edge of the second full strip over the
inner edge of the first strip laid, you must
position the outer edge of the second full strip 8
2/3 inches from the outer edges of the first three
strips. To maintain the same overlap, lay the
outer edge of the third full strip 10 1/3 inches
from the outer edge of the second full strip.
Subsequent strips can be laid with an exposure
of 10 inches. Finish off at the opposite edge of
the roof with a full strip, two-thirds of a strip,
and one-third of a strip to maintain three plies
throughout.
6. Spread a layer of hot asphalt (the flood coat)
over the entire roof.
7. Sprinkle a layer of gravel, crushed stone, or slag
over the entire roof.
Melt the binder and maintain it at the proper
temperature in a pressure fuel kettle. Make sure the
kettle is suitably located. Position it broadside to the
wind, if possible. The kettle must be set up and kept
level. If it is not level, it will heat unevenly, creating a
hazard. The first duty of the kettle operator is to inspect
the kettle, especially to ensure that it is perfectly dry.
Any accumulation of water inside will turn to steam
when the kettle gets hot. This can cause the hot binder
to bubble over, which creates a serious fire hazard.
Detailed procedure for lighting off, operating, servicing,
and maintaining the kettle is given in the manufacturer’s
manual. Never operate the kettle unattended, while the
trailer is in transit, or in a confined area.
The kettle operator must maintain the binder at a
steady temperature, as indicated by the temperature
gauge on the kettle. Correct temperature is designated
in binder manufacturer’s specifications. For asphalt, it
is about 400°F. The best way to keep an even
temperature is to add material at the same rate as melted
material is tapped off. Pieces must not be thrown into
the melted mass, but placedon the surface, pushed under
slowly, and then released. If the material is not being
steadily tapped off, it may eventually overheat, even
with the burner flame at the lowest possible level. In that
case, the burner should be withdrawn from the kettle and
placed on the ground to be reinserted when the
temperature falls. Prolonged overheating causes
flashing and impairs the quality of the binder.
Asphalt or pitch must not be allowed to accumulate
on the exterior of the kettle because it creates a fire
hazard. If the kettle catches fire, close the lid
immediately, shut off the pressure and burner valves,
and, if possible, remove the burner from the kettle.
Never attempt to extinguish a kettle fire with water. Use
sand, dirt, or a chemical fire extinguisher.
A hot rooting crew consists of a mopper and as
many felt layers, broomers, nailers, and carriers as the
size of the roof requires. The mopper is in charge of the
roofing crew. It is the mopper’s personal responsibility
to mop on only binder that is at the proper temperature.
Binder that is too hot will burn the felt, and the layer it
makes will be too thin. A layer that is too thin will
eventually crack and the felt may separate from the
binder. Binder that is too cold goes on too thick so more
material is used than is required.
The felt layer must get the felt down as soon as
possible after the binder has been placed. If the interval
between mopping and felt laying is too long, the binder
will cool to the point where it will not bond well with
the felt. The felt layer should follow the mopper at an
interval of not more than 3 feet. The broomer should
follow immediately behind the felt layer, brooming out
all air bubbles and embedding the felt solidly in the
binder.
Buckets of hot binder should never be filled more
than three-fourths full, and they should never be carried
any faster than a walk. Whenever possible, the mopper
should work downwind from the felt layer and broomer
to reduce the danger of spattering. The mopper must
take every precaution against spattering at all times. The
mopper should lift the mop out of the bucket, not drag
it across the rim. Dragging the mop over the rim may
upset the bucket, and the hot binder may quickly spread
to the feet, or worse still to the knees, of nearby members
of the roofing crew.
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