§ 27-338 Roof structures.
AC § 27-338
(a)Construction of penthouses. Enclosure walls of penthouses shall comply with the requirements for exterior walls of table 3-4 for the construction class of the building on which they are erected. Roofs of penthouses shall comply with the requirements for roof construction of table 3-4 and section 27-337 of article five of subchapter six of this chapter.
(b)Construction of bulkheads. Bulkheads shall be constructed of noncombustible materials having a one hour fire-resistance rating, except that in buildings of construction class II-E, they may be constructed of combustible materials having a one hour fire-resistance rating.
(c)Scuttles. Scuttles shall be constructed of noncombustible materials, or of combustible materials covered on the top, sides, and edges with noncombustible materials.
(d)Skylights. For the purposes of this section, the term "skylight" shall be construed to include the sash, frames, and glazing of roof monitors and sawtooth roofs.
(1)SASH AND FRAMES. Skylights that are inclined at less than sixty degrees to the horizontal on all buildings of other than construction classes II-D and II-E, shall have sash and frames constructed of noncombustible materials, and their glazing shall be as prescribed in paragraph two of this subdivision. Skylights that are inclined at greater than sixty degrees to the horizontal shall have sash and frames constructed as required for windows, and their glazing shall be as required for windows. Glass, glass blocks, or plastic used in skylights shall be designed and constructed to withstand the same live loads as required for roofs plus any concentrated live loads required herein.
(2)GLAZING. a. Skylights over stairways and shafts. Skylights placed over stairways and shafts shall be glazed with plain glass not more than one-eighth inch thick or unreinforced plastic not more than three-sixteenths of an inch thick. b. Skylights over other spaces. Skylights in all locations other than over stairways and shafts shall be glazed with one-quarter inch wired glass, plain glass, glass block, or plastic of material and installation complying with subparagraph c of this paragraph. c. Plastic. Plastic used for the glazing of skylights other than skylights over stairways and shafts shall be slow burning plastic. The aggregate area of skylight openings, other than over stairways and shafts, shall not exceed thirty-nine per cent of the floor area of any room or space sheltered by the roof in which they are located. The edges of plastic, if exposed, shall be protected by metal or other noncombustible material. Skylights in which plastic is used, if on roofs having a pitch of twenty degrees to the horizontal or less, shall be constructed in accordance with the following: 1. The area within the curbs of each skylight shall not exceed five square feet, except that this area may be of any size, limited only by other provisions of this section,if the opening is protected on all sides by a noncombustible railing thirty-six inches in height complying with the provisions of section 27-558 of article three of subchapter nine of this chapter for railings; or the skylight is subdivided into areas of five square feet or less by noncombustible muntins or bars capable of supporting a live load of three hundred pounds at any point; or a noncombustible screen or grid capable of supporting a load of three hundred pounds over any one foot by two foot area as provided above, integral with, or not more than three feet below the skylight, with the wire or bars spaced into areas of five square feet or less (if above the roof, the wires shall be of corrosion resistive metal).
2.There shall be a minimum clear distance of three feet between skylights.
(3)Separation of skylights from structures. There shall be at least ten feet between a plain glass or plastic skylight and any door in a stair bulkhead located above the roof in which the skylight is located, and at least ten feet between such a skylight and any opening in any roof structure or other wall above the roof not equipped with an opening protective. On buildings up to one hundred feet in height there shall be at least ten feet from such a skylight to the outside face of an exterior wall facing on a frontage space.
(4)SCREENS. Plain glass skylights shall be protected on their underside by noncombustible screens having a mesh not smaller than three-quarters of an inch by three-quarters of an inch nor larger than one inch by one inch of at least No. 12 B. & S. gauge wires. The screen shall be installed tight against the roof opening or shall project on all sides for a distance of not less than the distance of the screen below the glass, and shall be of such material and construction so as to support a load of three hundred pounds over any one foot by two foot area. The provisions for wire glass or screen protection shall not apply to glass block skylights.
(e)Greenhouses. Greenhouses on the roofs of buildings other than buildings of construction class II-D or II-E shall be constructed of noncombustible framework and shall be glazed with plain or wire glass, or slow burning plastic. The floors of greenhouses shall be constructed at least as required for roof construction in table 3-4 for the construction class of the building on which it is located.
(f)Construction of sloping roofs. Roofs having a slope of more than sixty degrees to the horizontal shall be constructed of material having the same fire-resistance rating as required for an exterior non-bearing wall of the building of which it is a part. When the slope is sixty degrees or less to the horizontal, the sloping roof shall be constructed as required for the roof of the building. Where the back of a false mansard is exposed to the outdoors, the back shall be covered with noncombustible material or with roof coverings as required for the roof of the building.
(g)Dormers. Roofs of dormers shall be of the same type of construction and have roof covering of the same class as required for the roof of the building on which they are located. The walls of dormers shall be constructed of materials having the same fire resistance rating as required for non-bearing exterior walls of the building on which they are located; except that in buildings of construction classes II-A, II-B, II-C, and II-D, the walls may be constructed of combustible framing provided that the outside face of the framing is protected with noncombustible sheathing and the aggregate area of all such dormer walls, including openings therein, does not exceed twenty percent of the roof area.
(h)Water tanks.
(i)Cooling towers. Cooling towers shall be constructed of noncombustible materials, except as follows: (1) Outside the fire districts, when located on a building three stories or forty feet in height or less of construction group I, cooling towers may be constructed of combustible materials provided they are not more than fifteen feet high and do not exceed seven hundred fifty square feet in area.
(5)In no event shall cooling towers or filling and drift eliminators be constructed of materials that contain asbestos.
(j)Miscellaneous roof structures. The following roof structures may be constructed of combustible material if less than twelve feet high above the roof: antenna supports; flagpoles; clothes drying frames; duckboarding or platforms that do not cover more than twenty per cent of the roof area at that level.
