§ 27-561 Roof loads.
AC § 27-561
Roofs and marquees shall be designed for wind, live, and other loads as prescribed in subdivisions (a) through (d) of this section. It may be assumed that maximum wind load occurs with zero live load and that maximum live load occurs with zero wind load. For dwellings an exception is made for awnings, canopies, and patio covers, which may be designed for a live load of twenty psf of horizontal projection.
(a)Live load. Minimum design live loads shall be as follows: (1) For roofs with slopes up to and including twenty degrees from the horizontal, thirty psf of horizontal projection.
(2)For roofs with slopes greater than twenty degrees from the horizontal, thirty psf of horizontal projection, reduced by one psf for each degree of slope in excess of twenty degrees.
(3)For valleys, live loadings shall be increased to provide for accumulations of snow. The loading intensity shall be assumed to vary from forty-five psf at the low point to fifteen psf at the ridge.
(4)For roofs having curved or pyramidal shapes, the proposed live load shall be established by the architect or engineer, subject to approval by the commissioner.
(b)Wind load. The provisions of section 27-569 of article five of this subchapter shall apply.
(c)Concentrated loads. The provisions of subdivision (b) of section 27-557 of this article shall apply.
(d)Special loads.
(1)When used for purposes such as promenades, assembly areas, or roof gardens, design shall be made for live loads corresponding to the particular usage, as indicated in reference standard RS 9-2. Such loads shall be considered as nonconcurrent with the wind load or with the live load specified in subdivision (a) of this section. The design live and wind loads for roofs, as specified elsewhere in this subchapter, shall be deemed to provide for incidental use of the roof of a building by the occupants thereof.
(5)Where equipment is placed on roofs, the design shall provide for the support of such equipment.
