Current through Register 1531, September 27, 2024
2304.8.1
General. Lumber decking shall be designed and installed in accordance
with the general provisions of this code and Section 2304.8. Each piece shall
be square end trimmed. When random lengths are furnished, each piece shall be
square end trimmed across the face so that at least 90 percent of the pieces
are within 0.5 degrees (0.00873 rad) of square. The ends of the pieces shall be
permitted to be beveled up to 2 degrees (0.0349 rad) from the vertical with the
exposed face of the piece slightly longer than the opposite face of the piece.
Tongue-and-groove decking shall be installed with the tongues up on sloped or
pitched roofs with pattern faces down.
2304.8.2
Layup patterns. Lumber
decking is permitted to be laid up following one of five standard patterns as
defined in Sections 2304.8.2.1 through 2304.8.2.5. Other patterns are permitted
to be used provided they are substantiated through engineering analysis.
2304.8.2.1
Simple span pattern.
All pieces shall be supported on their ends (i.e., by two supports).
2304.8.2.2
Two-span continuous
pattern. All pieces shall be supported by three supports, and all end
joints shall occur in line on alternating supports. Supporting members shall be
designed to accommodate the load redistribution caused by this
pattern.
2304.8.2.3
Combination simple and two-span continuous pattern. Courses in end spans
shall be alternating simple-span pattern and two-span continuous pattern. End
joints shall be staggered in adjacent courses and shall bear on
supports.
2304.8.2.4
Cantilevered pieces intermixed pattern. The decking shall extend across
a minimum of three spans. Pieces in each starter course and every third course
shall be simple span pattern. Pieces in other courses shall be cantilevered
over the supports with end joints at alternating quarter or third points of the
spans. Each piece shall bear on at least one support.
2304.8.2.5
Controlled random
pattern. The decking shall extend across a minimum of three spans. End
joints of pieces within 6 inches (152 mm) of the end joints of the adjacent
pieces in either direction shall be separated by at least two intervening
courses. In the end bays, each piece shall bear on at least one support. Where
an end joint occurs in an end bay, the next piece in the same course shall
continue over the first inner support for at least 24 inches (610 mm). The
details of the controlled random pattern shall be as specified for each decking
material in Section 2304.8.3.3, 2304.8.4.3 or 2304.8.5.3.
Decking that cantilevers beyond a support for a horizontal
distance greater than 18 inches (457 mm), 24 inches (610 mm) or 36 inches (914
mm) for 2-inch (51 mm), 3-inch (76 mm) and 4-inch (102 mm) nominal thickness
decking, respectively, shall comply with the following:
1. The maximum cantilevered length shall be
30 percent of the length of the first adjacent interior span.
2. A structural fascia shall be fastened to
each decking piece to maintain a continuous, straight line.
3. There shall be no end joints in the
decking between the cantilevered end of the decking and the centerline of the
first adjacent interior span.
2304.8.3
Mechanically laminated
decking.
2304.8.3.1
General. Mechanically laminated decking consists of square-edged
dimension lumber laminations set on edge and nailed to the adjacent pieces and
to the supports.
2304.8.3.2
Nailing. The length of nails connecting laminations shall not be less
than two and one-half times the net thickness of each lamination. Where decking
supports are 48 inches (1219 mm) on center (o.c.) or less, side nails shall be
installed not more than 30 inches (762 mm) o.c. alternating between top and
bottom edges, and staggered one-third of the spacing in adjacent laminations.
Where supports are spaced more than 48 inches (1219 mm) o.c., side nails shall
be installed not more than 18 inches (457 mm) o.c. alternating between top and
bottom edges and staggered one-third of the spacing in adjacent laminations.
Two side nails shall be installed at each end of butt-jointed pieces.
Laminations shall be toenailed to supports with 20d or larger
common nails. Where the supports are 48 inches (1219 mm) o.c. or less,
alternate laminations shall be toenailed to alternate supports; where supports
are spaced more than 48 inches (1219 mm) o.c., alternate laminations shall be
toenailed to every support.
2304.8.3.3
Controlled random
pattern. There shall be a minimum distance of 24 inches (610 mm) between
end joints in adjacent courses. The pieces in the first and second courses
shall bear on at least two supports with end joints in these two courses
occurring on alternate supports. A maximum of seven intervening courses shall
be permitted before this pattern is repeated.
2304.8.4
Two-inch sawn
tongue-and-groove decking.
2304.8.4.1
General. Two-inch (51 mm) decking shall have a maximum moisture
content of 15 percent. Decking shall be machined with a single
tongue-and-groove pattern. Each decking piece shall be nailed to each
support.
2304.8.4.2
Nailing. Each piece of decking shall be toenailed at each support with
one 16d common nail through the tongue and face-nailed with one 16d common
nail.
2304.8.4.3
Controlled
random pattern. There shall be a minimum distance of 24 inches (610 mm)
between end joints in adjacent courses. The pieces in the first and second
courses shall bear on at least two supports with end joints in these two
courses occurring on alternate supports. A maximum of seven intervening courses
shall be permitted before this pattern is repeated.
2304.8.5
Three- and 4-inch sawn
tongue-and-groove decking.
2304.8.5.1
General. Three-inch (76 mm) and 4-inch (102 mm) decking shall
have a maximum moisture content of 19 percent. Decking shall be machined with a
double tongue-and-groove pattern. Decking pieces shall be interconnected and
nailed to the supports.
2304.8.5.2
Nailing. Each piece shall be toenailed at each support with one
40d common nail and face-nailed with one 60d common nail. Courses shall be
spiked to each other with 8-inch (203 mm) spikes at maximum intervals of 30
inches (762 mm) through predrilled edge holes penetrating to a depth of
approximately 4 inches (102 mm). One spike shall be installed at a distance not
exceeding 10 inches (254 mm) from the end of each piece.
2304.8.5.3
Controlled random
pattern. There shall be a minimum distance of 48 inches (1219 mm)
between end joints in adjacent courses. Pieces not bearing on a support are
permitted to be located in interior bays provided the adjacent pieces in the
same course continue over the support for at least 24 inches (610 mm). This
condition shall not occur more than once in every six courses in each interior
bay.
