Untitled - National Roofing Contractors Association

wood sheathing with exterior glue as C-DX, the "X"
(which refers to Exterior Glue) is not used in label
A. The EXPOSURE 1 classification is typically interior
type panel with exterior glue.
P8n8I Grade
=APA-
RATED SHEATHING
Sp8n RaI81g 32/16 15/32 INCH ~
EMP(.ure
SIZED FOR S~ING
~ EXPOSURE 1
dassitK:al~ 000 Mil n.-nbef
Code recogM~ 01 - NER.QA387 PHp.", -APA.s Perkwmance-RaIed
APA as a CJJMty
PanS STandard
8S9Jr~ 99Br-=v
which does not comply with PS 1-83 in certain
respects. A label similar to one of these should be
found on each sheet of wood panel used.
The Span Rating (32/16 in these labels) is of particular
significance. The left-hand number of the Span
Rating (32 in these labels) indicates the maximum
recommended center-to-center spacing of supports
in inches when the panel is used for roof decking
with the long dimension of the panel running across
the supports. The right-hand number of the Span
Rating (16 in these labels) indicates the maximum
recommended spacing of supports in inches when
the panel is used for subflooring in double-layer construction
with the long dimension of the panel running
across the supports. Therefore, the Span Rating
of 32/16 in these labels mean that a particular
wood panel may be used either for roof decking over
supports that are spaced 32 inches on center or for
subflooring over supports that are spaced 16 inches
on center. In all cases, panels are assumed continuous
over two or more spans.
Note: Though the industry termin04ogy refers to ply-
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End joints of the wood panels should be staggered
and supported by framing members, and deck support
clips should be installed on the unsupported
sides of the wood panel sheets. Temporary protection
should be provided by the installer to prevent
entry of moisture into the panels. (See Section III,
Temporary Roofs.)
A slip sheet of dry sheathing paper is recommended
for use over wood plank decks but is not needed
over wood panel decks. It is good practice, however,
to nail a minimum layer of insulation over wood panel
decks. On panel decks not covered with insulation,
a base ply should be mechanically fastened over the
wood panel deck (preferably with annular threaded
nails) to serve as the base ply of the roof membrane.
SPECIAL NOTE: NRCA is concerned regarding
potential fastener holding problems where oriented
strand board and waferboard products are used as
the roof deck component. Please refer to the roofing
manufacturers' specifICations for acceptable roof
deck materials.
XIX. ROOF MEMBRANES
Each built-up roof system is designed to satisfy a specific
set of conditions for substrate, life span, roof slope and
climate. The designer should relate these conditions to
field conditions in order to determine the proper specifications.
The geographical location and climatic conditions
to be encountered frequently determine the type
of membrane to be installed. A roof membrane in Arizona,
where there is little rainfall and extreme sunlight, may
require a different roof system than one in Montana, with
its extreme temperature variances.
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