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Title: Section 504  •  Size: 12092

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SECTION 504 - ALLOWABLE FLOOR AREAS

504.1 One-story Areas. The area of a one-story building shall not exceed the limits set forth in Table 5-B except as provided in Section 505.

504.2 Areas of Buildings over One Story. The total combined floor area for multistory buildings may be twice that permitted by Table 5-B for one-story buildings, and the floor area of any single story shall not exceed that permitted for a one-story building.

504.3 Allowable Floor Area of Mixed Occupancies. When a building houses more than one occupancy, the area of the building shall be such that the sum of the ratios of the actual area for each separate occupancy divided by the total allowable area for each separate occupancy shall not exceed one.

EXCEPTIONS: 1. The major occupancy classification of a building may be used to determine the allowable area of such building when the major use occupies not less than 90 percent of the area of any floor of the building and provided that other minor accessory uses shall not exceed the basic area permitted by Table 5-B for such minor uses and that various uses are separated as specified in Section 302.4.

2. Groups B, F, M and S and Group H, Division 5 Occupancies complying with the provisions of Section 505.2 may contain other occupancies provided that such occupancies do not occupy more than 10 percent of the area of any floor of a building, nor more than the basic area permitted in the occupancy by Table 5-B for such occupancy, and further provided that such occupancies are separated as specified in Section 302.4.

504.4 Mezzanines. Unless considered as a separate story, the floor area of all mezzanines shall be included in calculating the allowable floor area of the stories in which the mezzanines are located.

504.5 Basements. A basement need not be included in the total allowable area, provided such basement does not exceed the area permitted for a one-story building.

504.6 Area Separation Walls.

504.6.1 General. Each portion of a building separated by one or more area separation walls which comply with the provisions of this subsection may be considered a separate building. The extent and location of such area separation walls shall provide a complete separation.

When an area separation wall also separates occupancies that are required to be separated by an occupancy separation, the most restrictive requirements of each separation shall apply.

504.6.2 Fire resistance and openings. Area separation walls shall not be less than four-hour fire-resistive construction in Types I, II-F.R., III and IV buildings and two-hour fire-resistive construction in Types II One-hour, II-N or V buildings. The total width of all openings in such walls shall not exceed 25 percent of the length of the wall in each story. All openings shall be protected by a fire assembly having a three-hour fire-protection rating in four-hour fire-resistive walls and one- and one-half-hour fire-protection rating in two-hour fire-resistive walls.

504.6.3 Extensions beyond exterior walls. Area separation walls shall extend horizontally to the outer edges of horizontal projecting elements such as balconies, roof overhangs, canopies, marquees or architectural projections extending beyond the floor area as defined in Section 207.

EXCEPTIONS: 1. When horizontal projecting elements do not contain concealed spaces, the area separation wall may terminate at the exterior wall.

2. When the horizontal projecting elements contain concealed spaces, the area separation wall need only extend through the concealed space to the outer edges of the projecting elements.

In either Exception 1 or 2, the exterior walls and the projecting elements above shall not be of less than one-hour fire-resistive construction for a distance not less than the depth of the projecting elements on both sides of the area separation wall. Openings within such widths shall be protected by fire assemblies having a fire-protection rating of not less than three-fourths hour.

504.6.4 Terminating. Area separation walls shall extend vertically from the foundation to a point at least 30 inches (762 mm) above the roof.

EXCEPTIONS: 1. Any area separation wall may terminate at the underside of the roof sheathing, deck or slab, provided the roof-ceiling assembly is of at least two-hour fire-resistive construction.

2. Two-hour area separation walls may terminate at the underside of the roof sheathing, deck or slab, provided:

2.1 When the roof-ceiling framing elements are parallel to the walls, such framing and elements supporting such framing shall not be of less than one-hour fire-resistive construction for a width of not less than 5 feet (1524 mm) on each side of the wall.

2.2 When roof-ceiling framing elements are perpendicular to the wall, the entire span of such framing and elements supporting such framing shall not be of less than one-hour fire-resistive construction.

2.3 Openings in the roof shall not be located within 5 feet (1524 mm) of the area separation wall.

2.4 The entire building shall be provided with not less than a Class B roof covering as specified in Table 15-A.

3. Two-hour area separation walls may terminate at the underside of noncombustible roof sheathing, deck or slabs of roofs of noncombustible construction provided:

3.1 Openings in the roof are not located within 5 feet (1524 mm) of the area separation wall.

3.2 The entire building is provided with not less than a Class B roof covering as specified in Table 15-A.

504.6.5 Parapet faces. Parapets of area separation walls shall have noncombustible faces for the uppermost 18 inches (457 mm), including counterflashing and coping materials.

504.6.6 Building of different heights. Where an area separation wall separates portions of a building having different heights, such wall may terminate at a point 30 inches (762 mm) above the lower roof level, provided the exterior wall for a height of 10 feet (3048 mm) above the lower roof is of one-hour fire-resistive construction with openings protected by assemblies having a three-fourths-hour fire-protection rating.

EXCEPTION: Two-hour area separation walls may terminate at the underside of the roof sheathing, deck or slab of the lower roof, provided:

1. When the roof-ceiling framing elements are parallel to the wall, such framing and elements supporting such framing shall not be of less than one-hour fire-resistive construction for a width of 10 feet (3048 mm) along the wall at the lower roof.

2. When the lower roof-ceiling framing elements are perpendicular to the wall, the entire span of such framing and elements supporting such framing shall not be of less than one-hour fire-resistive construction.

3. Openings in the lower roof shall not be located within 10 feet (3048 mm) of the area separation wall.

See Chapters 3 and 4 for special occupancy provisions.

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