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Title: Section 1605 • Size: 8145
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1605.1 General. Roofs shall sustain, within the stress limitations of this code, all dead loads plus unit live loads as set forth in Table 16-C. The live loads shall be assumed to act vertically upon the area projected upon a horizontal plane.
EXCEPTION: Alternate span
loading need not be considered where the uniform roof live load
is 20 pounds per square foot (0.96 kN/)
or more or the provisions of Section 1605.4
are met.
For those conditions where light-gage metal preformed structural sheets serve as the support and finish of roofs, roof structural members arranged so as to create continuity shall be considered adequate if designed for full dead loads on all spans in combination with the most critical one of the following superimposed loads:
1. Snow load in accordance with Section 1605.4.
2. The uniform live load set forth in Table 16-C on all spans.
3. A concentrated gravity load of 2,000 pounds
(8.9 kN) placed on any span supporting a tributary area greater
than 200 square feet (18.58 ) so as
to create maximum stress in the member whenever this loading creates
greater stresses than those caused by the
uniform live load. The concentrated load shall be placed on
the member over a length of 21/2 feet (762 mm) along the span.
The 2,000-pound (8.9 kN) load need not be applied to more than
one span simultaneously.
4. Water accumulation as prescribed in Section 1605.6.
1605.4 Snow Loads. Snow loads full or unbalanced shall be considered in place of loads set forth in Table 16-C, where such loading will result in larger members or connections.
Potential unbalanced accumulation of snow at valleys, parapets, roof structures and offsets in roofs of uneven configuration shall be considered. Where snow loads occur, the snow loads shall be determined by the building official.
Snow loads in excess of 20 pounds per square foot
(0.96 kN/) may be reduced for each degree
of pitch over 20 degrees by
as determined
by the following formula:
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For SI: | ![]() |
WHERE:
= snow load reduction in
pounds per square foot (kN/
) per degree
of pitch over 20 degrees.
S = total snow load in
pounds per square foot (kN/).
For alternate design procedure see Appendix Chapter 16, Division I.
Greenhouse roof bars, purlins and rafters shall be designed to carry a 100-pound-minimum (444.8 N) concentrated load in addition to the live load.
1605.6 Water Accumulation. All
roofs shall be designed with sufficient slope or camber to assure
adequate drainage after the long-time deflection from dead load
or shall be designed to support maximum loads, including possible
ponding of water from any source, including snow, due to deflection.
See Section 1608 for deflection
criteria.
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