Untitled - National Roofing Contractors Association

Coal-tar roofing products are described by ASTM Standard
0-450, Types I & III, "Coal Tar Pitch Used in Roofing,
Dampproofing and Waterproofing." Types I & "' are
suitable for use in the construction of coal tar built-up
roofing, the difference being that Type III has less volatile
components than Type I. The Equiviscous Temperature
(EVT) concept is equaJly applicable to coal tar
products, although the recommended viscosity base is
considerabfy lower for the coal tar products than for roofing
asphalts. In the event the information is not furnished
by the supplier, the following temperature ranges appear
to be appropriate for coal tar for ~h mechanicaJ spreader
and mopping application techniques:
. Coal Tar Pitch (Type I) approximately 360 F plus
or minus 25 F
. Coal Tar Bitumen (Type III) approximately 375 F
plus or minus 25 F
XXI. WATER CUTOFFS AND
WEATHER PROTECTION
Water cutoffs are temporary felt courses that are installed
to prevent moisture from entering the insulation and
membrane during construction. They should be applied
at the end of each day's work and whenever work is halted
for an indefinite period to protect the membrane from
precipitation. They must be removed prior to installing
additional insulation.
Temporary flashings should be installed as weather protection
If permanent flashings are not in place. All openings
in the membrane should be sealed to prevent any
moisture from entering the roof system before completing
membrane application.
Specifications requiring gravel installation each day are
unrealistic and sometimes detrimental to the quality of
the completed roof. Where working conditions permit,
roofing felts should be "glazed" and sealed at the end
of each day's work if final surfacing is not installed.
The most vulnerable part of any roof system is that point
at which the horizontal roof deck and a vertical surface
join. Most roof leaks occur at these flashing locations.
The designers should carefully consider the design of
flashing details at these locations. (See NRCA Construction
Details in the NRCA Roofing and Waterproofing
Manua/.)
The term flashing can be divided into two groups:
1. Composition Flashing (Base Flashing)
The bending radius of present composition roofing
materials is generally limited to 45 degrees. To allow
for this bending radius, all vertical surfaces must
have cant strips installed between the roof and the
vertical surface. The height of the base flashing
should be not lower than (a nominal) 8 inches and
not higher than (a nominal) 14 inches above the
finished roof surface. Walls requiring flashings
higher than 14 inches should receive special
moisture-proofing. A wood nailer strip or suitable detail
allowing mechanical fastening of the base flashing
at the top must be provided. Masonry surfaces
should be primed with asphalt concrete primer.
Expansion joint flashings (allowing expansion and
contraction) should be constructed as detailed in the
NRCA Construction Details. The wood curbing
should be placed against the wall and secured only
to the deck. The designer is cautioned to consider
that building components are subjected to thermal
movements at different rates and in different directions
from the roof membrane. If the roof is to be tied
into these components, special consideration should
be given to the design of that juncture.
2. Metal Flashing (Counterflashlng and Cap
Flashing)
Since metals have a high coefficient of expansion.
metal flashing must be isolated from the roof mem-
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