Ann Arbor — Ch. 105 Housing Code § 8:504

All dwellings must have adequate exits. (1)
Inadequate exits. If a multiple dwelling does not have the exits required for new buildings, it shall be equipped with the additional facilities that the Building Official judges necessary for safety to comply with this chapter.
(2) New exitways. If new or altered exit facilities are installed or constructed, they shall comply with all the requirements of this chapter or of Chapter 100 , as ordered by the Building Official.
(3) Required exits.
(a) Every floor and unit in a multiple dwelling, except floors and units at grade, including the basement or cellar, shall have at least 2 separate approved ways of exit. All required exit stairs shall be 1 hour rated enclosures. All doors opening into the exitway or exitway access shall have approved self-closing and latching devices. Casement windows may be used as an opening to a second exit if they meet the standards for casement windows leading to fire escapes.
(b) Multiple dwellings with not more than 2 above grade stories and not more than 4 dwelling units per floor may have 1 exit if they conform to the following: The length of exit travel shall be less than 50 feet and the exitway shall be 1-hour rated. Doors opening into the exitway shall have approved self-closing and latching devices.
(c) Emergency escape window: Every sleeping area in 1-family, 2-family, and terrace family dwellings shall have an emergency escape window unless the sleeping area has access on the same floor to 2 approved ways of exit. Every sleeping area of grade floor units in multiple dwellings shall have an emergency escape window unless the sleeping area has access on the same floor to 2 approved means of exit.
(d) The emergency escape window shall have a minimum clear opening width of 20 inches and a clear opening height of 20 inches. The clear opening width may be reduced to a minimum of 14 inches, provided that the net clear opening area is a minimum of 500 square inches or the clear height may be reduced to a minimum of 16 inches provided the clear opening is a minimum of 500 square inches. Bars, grills or screens placed over emergency escape windows shall be releasable or removable from the inside, without the use of a key, tools, or excessive force. The maximum sill height shall be 54 inches above the floor. If the existing sill height is greater than 54 inches above the floor, a platform, structure or piece of furniture (not including a shelf) permanently affixed to the structure will be acceptable provided it has a minimum depth of 12 inches, a minimum width of 20 inches is a maximum of 18 inches above the floor, is no more than 44 inches below the sill and is located beneath the openable portion of this window.
(4) Fire exits.
(a) Exit corridors.
1. Exit corridors must have a clear width of at least 27 inches.
2. Exit corridors shall have a ceiling height of at least 6 feet 6 inches.
3. Corridor headroom shall be measured at the midpoint of the required width. For corridors with ceilings which slope from side to side the required width shall begin at the high side.
(b) Exit stairways.
1. Exit stairways must be at least 27 inches wide.
2. Exit stairways shall have a minimum ceiling height of 6 feet. Height measurement shall be from a line tangent to the nosing of the treads to the ceiling measured at the midpoint of the required width. For stairs with ceilings which slope from side to side, the required width shall begin at the high side.
3. The risers shall be no more than 9 inches high.
4. The treads shall be not less than 9 inches deep.
5. A handrail shall be located 30 to 38 inches above the nosing of the treads (existing handrails at least 26 inches above the nosing of the treads may remain provided they are in good repair and meet the remaining requirements). It shall be installed on the side having the greater ceiling height. Where the stairs are open on any side, there shall be an approved handrail and an intermediate guard 12 to 15 inches above the stairs. Vertical balusters spaced not greater than 6 inches may be used in place of the intermediate guard.
6. Stairs shall be capable of supporting a live load of 100 pounds per square foot.
7. Stairways of 1- and 2 family dwellings may have a height of 5 feet 6 inches if there is an approved second exit from each upper floor or hardwired interconnected smoke detectors at the top of each flight of stairs.
8. Multiple and terrace family dwellings may have a stairway headroom height of 5 feet 6 inches at 1 location covering not more than 3 treads if there is an approved second exit for each upper floor, and if hardwired interconnected smoke detectors are installed at the top of each flight of stairs within a common stairwell. Stairs within a unit which do not meet the height requirement will be permitted if there is an approved second access from each upper floor and if they are hardwired interconnected smoke detectors at the top of each flight of stairs. This subsection applies only to dwellings, dwelling units or rooms built before January 1, 1989.
9. In multiple dwelling, no materials shall be stored and no storage area may be established under an exit corridor or stairway, unless that storage area is enclosed and properly fire rated.
(5) Fire escapes. An unenclosed fire escape may be used as a second exit in a multiple dwelling or rooming dwelling if it conforms to the following:
(a) There is an approved exit stairway.
(b) Two exits are directly accessible to all occupants without passing through another dwelling or rooming unit.
(c) The fire escape shall be designed to support a live load of 100 pounds per square foot. It shall be constructed of steel, other approved noncombustible materials, or wood of not less than 2 inches nominal thickness. Fire escapes, when replaced, shall be 22 inches in width with risers not more, and treads not less than 8 inches. Stairs shall have a handrail 30 to 38 inches above the nosing of the treads and intermediate guards 12 to 15 inches above the nosing of the treads, placed on all open sides. Landings, platforms, and walkways shall have guardrails 42 inches high with intermediate rails not more than 15 inches apart. Vertical balusters spaced not greater than 6 inches apart may be used in place of the intermediate guards. There shall be a minimum 6 feet [of] headroom throughout the fire escape.
(d) Access to a fire escape shall be provided by a door or casement window with a width of not less than 27 inches and a height of not less than 47 inches or a width of not less than 22 inches and a height of not less than 53 inches. Access to a fire escape used by only 1 unit shall be through an opening with a width of not less than 22 inches and a height of not less than 47 inches. Doors serving more than 1 unit shall open in the direction of egress.