(a) Size. (1) A dwelling unit shall contain at least one habitable space which shall have a minimum floor area of 150 square feet with a minimum horizontal dimension of 10 feet. Other habitable spaces, except kitchens, shall have a minimum floor area of 80 square feet with a minimum horizontal dimension of 7 feet.
(2) Habitable space shall have a minimum height of 7 feet 6 inches, except that for habitable space under a sloping roof the minimum height in at least 50 percent of the floor area shall be 7 feet 6 inches and the area where the height is less than five feet shall not be considered in computing required floor area.
(3) Where exposed beams project below the ceiling of habitable space, and such beams occupy an area of five percent or more of the area of the ceiling, the height of the space shall be measured from finished floor to the underside of beams. Where the ration is less that five percent, the height to the underside of beam shall be not less than 7 feet.
(b) Location in respect to grade level. Floor
level of habitable space shall be not more than four feet below the average adjoining finished grade. No habitable space shall be located in cellars, except that below-grade space is permitted as habitable space where in conformity with the following conditions:
(a) Light. (1) Habitable space, except kitchen, shall be provided with natural light through one or more windows, skylights, transparent or translucent panels or any combination thereof, that face directly on legal open spaces at least five feet wide above the adjoining finished grade, or above a roof. The amount of light shall be equivalent to that transmitted through clear glass equal in area to not less than eight percent of the floor area of the habitable space.
(2) Kitchens shall be provided with artificial lighting equipment and may also be provided with natural light.
(b) Ventilation. Habitable space shall be provided with ventilation in accordance with either of the following:
(1) natural ventilation through openable parts of windows or other openings in exterior walls that face legal open spaces at least five feet wide above the adjoining finished grade or above a roof, or through openable parts of skylights, providing total clear ventilation area equal to not less than four percent of the total floor area of each habitable space.
(b) Treads. (1) Minimum width of treads of fixed stairs shall be nine inches plus 1 1/8 inch nosing for closed riser type, or nine inches for open riser type.
(4) Treads shall be level and all other than winder treads shall be uniform in width, with no variation exceeding one-eighth inch in any one run of stairs.
(c) Risers. (1) Maximum heights of risers shall be 8 1/4 inches except that the maximum height of risers of folding or disappearing stairs, exterior stairs to basements or cellars, and of other stairs intended for occasional use only, shall be nine inches.
(2) There shall be no variation exceeding one-eighth inch in the height of risers in any one run of stairs.
(d) Width. Widths of stairs shall be not less than 2 feet 8 inches clear between handrails or between handrail and opposite wall surface; except that stairs to a cellar or attic shall not be less than 2 feet 6 inches clear between handrails or between handrail and opposite wall surface.
(e) Headroom. The minimum clear headroom over any portion of any fixed stair tread shall be not less than 6 feet 6 inches measured vertically from the surface of the tread, except that the minimum shall be not less than 6 feet 4 inches over stairs from a second story to a third story and over stairs to a basement or to a cellar.
(f) Handrails and railings. (1) Stairs or steps of more than three risers shall have a handrail or railing parallel to the stair slope on at least one side. Where one or both sides of such stairs or steps are open, railings shall be provided on open sides.
(2) Window openings on stairs or landings, and well openings, shall be guarded by railings of other equivalent protection.
(3) Landings, platforms and porches more than 18 inches above the adjacent floor or grade level shall be provided with railings on the open sides, except where openings are required for access.
(4) Top surfaces of handrails and railings shall be not less than 30 inches nor more than 36 inches in height above the floor or tread level. On stair runs, the height shall be measured directly above the riser face.
(5) Clearance between handrail and supporting wall shall be not less than 1 1/2 inches.
(g) Landings. The swing of a door opening on a stairway shall not overlap the top step. Where landings are provided, their width shall be not less than the width of the stair of which they are a part.
(h)Light. Treads of stairs shall be lighted by either natural or artificial light of sufficient intensity to allow safe ascent and descent.
(a) Width. Main entrance door shall be at least 36 inches in width.
(b) Doors intended for passage shall be not less than 6 feet 8 inches in height.
Part 714.1 General Requirements - Openings for
Emergency Use
(c) Such openings shall not impede egress in an emergency, shall have a minimum area of four square feet, with a minimum dimension of 18 inches, with bottom of openings no higher than 3 feet 6 inches above finished floor in all above-grade stories, and no higher than 4 feet 6 inches where required in basement and cellar.
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