Stairway width

[Jerry Peck - Codeman]

From an e-mail question:

Jersey is there a min stairway width?

[Jerry Peck - Codeman]

I could not find the New Jersey Residential Code on-line, however, the New Jersey Residential Code is based on the International Residential Code, which is shown below:
(bold and underlining are mine)
- R15.7 Stairways.
- - R311.7.1 Width. Stairways shall not be less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height. Handrails shall not project more than 4.5 inches (114 mm) on either side of the stairway and the minimum clear width of the stairway at and below the handrail height, including treads and landings, shall not be less than 311/2 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.
- - - Exception: The width of spiral stairways shall be in accordance with Section R311.7.9.1.

The minimum width in almost every code for residential stairways has been 36 inches.

[babate]

Here's a link to the NJ Codes. http://www2.iccsafe.org/states/newjersey/

[Jerry Peck - Codeman]

[babate]

I agree, Jerry. The NJ Code is based on the ICC but offers modifications that appear to be left over from the BOCA (1996) code.

NYS adopted the ICC code with modifications, also. However, the modifications are seemingly more stringent than the NJ standards. For instance, the 2007 Building Code of New York State, Chapter 10 - Means of Egress, §1009 Stairways and Handrails states the following:

§1009.3 Stair treads and risers. Stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum. Stair tread depths shall be 11 inches (279 mm) minimum. The riser height shall be measured vertically between the leading edges of adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 0.375 inch (9.5 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at right angle to the tread's leading edge. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 0.375 inch (9.5
mm). Winder treads shall have a minimum tread depth of 11 inches (279 mm) measured at a right angle to the tread's leading edge at a point 12 inches (305 mm) from the side where the treads are narrower and a minimum tread depth of 10 inches (254 mm). The greatest winder tread depth at the 12-inch (305 mm) walk line within any flight of stairs shall not exceed the smallest by more than 0.375 inch (9.5 mm).

Exceptions:
1. Circular stairways in accordance with §1009.7.
2. Winders in accordance with §1009.8.
3. Spiral stairways in accordance with §1009.9.
4. Aisle stairs in assembly seating areas where the stair pitch or slope is set, for sightline reasons, by the slope of the adjacent seating area in accordance with §1024.11.2.
5. In occupancies in Group R-3, as applicable in §101.2, within dwelling units in occupancies in Group R-2, as applicable in Section 101.2, and in occupancies in Group U, which are accessory to an occupancy in Group R-3, as applicable in §101.2, the maximum riser height shall be 7.75 inches (197 mm) and the minimum tread depth shall be 10 inches (254 mm), the minimum winder tread depth at the walk line shall be 10 inches (254 mm), and the minimum winder tread depth shall be 6 inches (152 mm). A nosing not less than 0.75 inch (19.1 mm) but not more than 1.25 inches (32 mm) shall be provided on stairways with solid risers where the tread depth is less than 11 inches (279 mm).
6. See the Existing Building Code of New York State for the replacement of existing stairways.

Take note that the ICC standards were altered to a more restrictive standard and lowered to the ICC standard for R-3 occupancies by NYS. I believe this is a better representation of the ICC code council's reasoning than the less restrictive standard in NJ.

[Jerry Peck - Codeman]