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    Stairway width

    Stairway width

    New postby Jerry Peck - Codeman on Tue Sep 14, 2010 7:52 pm

    From an e-mail question:

    Jersey is there a min stairway width?
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    Re: Stairway width

    New postby Jerry Peck - Codeman on Tue Sep 14, 2010 8:02 pm

    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.
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    Re: Stairway width

    New postby babate on Fri Oct 01, 2010 1:31 pm

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

    New postby Jerry Peck - Codeman on Fri Oct 01, 2010 7:18 pm

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


    Thank you.

    At the time of my first reply I checked the ICC state codes online site and could not find the link to the New Jersey codes. Again, thank you for that link.

    Since my previous post I now have the NJ codes on my computer.

    The wording and widths are the same, the only difference are the section numbers.

    - R311.5 Stairways.
    - - R311.5.1 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 31.5 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 R311.5.8.

    The NJ Residential Code has changed the following for stairways:
    - x. In Section R311.4.3, Landings at doors, in Exception 2 and Exception 3, "7 3/4 inches (196 mm)" shall be
    deleted and "8 1/4 inches (210 mm)" shall be inserted. (My note: This allows for a much greater difference in elevation.)
    - xi. In Section R311.5.3.1, Riser height, in the first sentence, "7 3/4 inches (196 mm)" shall be deleted and "8
    1/4 inches (210 mm)" shall be inserted. (My note: This allows for a much steeper stair.)
    - xii. In Section 311.5.3.2, Tread depth, in the first sentence, "10 inches (254 mm)" shall be deleted and "9
    inches (229 mm)" shall be inserted. In addition, in the fourth sentence, "10 inches (254 mm)" shall be deleted
    and "9 inches (229 mm)" shall be inserted. (My note: This allows for a much steeper stair.)
    - xiii. In Section R311.5.6.1, Height, "34 inches (864 mm)" shall be deleted and "30 inches (762 mm)" shall be
    inserted. (My note: This allows for a much lower height for a handrail.)
    - xiv. In Section 311.5.6.3, Handrail grip size, Item 1 shall be deleted in its entirety and Section R315.2 of the
    2000 edition of the International Residential Code shall be inserted as follows:
    - - "Type 1. The handgrip portion of Type 1 handrails shall have a circular cross section of 1 1/4 inches (32 mm)
    minimum to 2 5/8 inches (67 mm) maximum. Other handrail shapes that provide an equivalent grasping surface
    are permissible. Edges shall have a minimum radius of 1/8 inch (3.2 mm)." (My note: This allows for a handrail which is less graspable.)
    - xv. Section R311.5.7, Illumination, shall be deleted in its entirety. (My note: This allow for stairways with NO illumination.)

    All in all, the NJ changes are, in my opinion, reducing the level of safety for stairways. When one considers that, historically, most falls occur in the home, and that falls on stairways can lead to greater injuries, one pauses with concern at what the reasoning behind the NJ changes might be, especially when compared to the standards adopted by the ICC in the IRC, which are widely accepted as providing an acceptable minimum level of safety. I could agree with increasing the level of safety with more stringent requirements (such as requiring stairs to be less steep with deeper treads and risers which are not as high, have handrails on both sides, etc.), but reducing the widely accepted level of safety for stairs?

    I understand that increasing the level of safety of stairs with the measures I mentioned comes with slightly higher construction costs; and that reducing the requirements for stairs likely results in slightly lower construction costs, but the overall cost to society from the small savings of construction costs is likely more than offset by the cost of injuries and associated recovery time, i.e., medical costs, lost wages, injuries which continue throughout the rest of ones life, etc.

    Let's presume that a stair has 17 risers and 16 treads, and that each tread is 1" less deep as stated in the NJ code, over 16 treads that saves 16" of run. Given that the minimum width of a stair is 36", an area 16 inches by 36 inches equals 566 square inches, or 3.93 square feet. Let's pluck a typical $100 per square foot construction cost out of the air (that cost varies around the country, but it should be more than adequate for smaller houses, and smaller houses is what the reduction in tread depth is directed toward), thus the construction cost savings for one stairway would be $393. The costs associated with even just one fall resulting in minimal injuries will far exceed $393.

    Anyway, that is my opinion.
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    Re: Stairway width

    New postby babate on Fri Oct 08, 2010 5:12 pm

    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.
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    Re: Stairway width

    New postby Jerry Peck - Codeman on Fri Oct 08, 2010 6:26 pm

    babate wrote:The NJ Code is based on the ICC but offers modifications that appear to be left over from the BOCA (1996) code.


    The BOCA code was the 1&2 Family Dwelling Code, which was the code the ICC IRC was derived from. The ICC IRC is the code the NJ IRC is based on. First I quoted the ICC IRC, then the NJ IRC.

    You quoted from the New York State Building Code, which is based on the ICC IBC, which has different requirements from the ICC IRC.

    The ICC IBC code is essentially the same as the NYS Building Code you quoted (see below for the IBC), did NYS adopt a code based on the ICC IRC?

    The IBC code section your NY Building Code was from:
    - 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 tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s leading edge. 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).
    - - Exceptions:
    - - - 1. Alternating tread devices in accordance with Section 1009.9.
    - - - 2. Spiral stairways in accordance with Section 1009.8.
    - - - 3. 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 Section 1025.11.2.
    - - - 4. In Group R-3 occupancies; within dwelling units in Group R-2 occupancies; and in Group U occupancies that are accessory to a Group R-3 occupancy or accessory to individual dwelling units in Group R-2 occupancies; the maximum riser height shall be 7.75 inches (197 mm); 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).
    - - - 5. See the Section 3403.4 for the replacement of existing stairways.

    The IBC addresses dwellings units as does the IRC, with the difference being that the IRC addresses *only* 1&2 family dwellings and townhouses of 3 stories or less, while the IBC dwelling unit sections refer to apartments, condos, hotels, and any other "residential" use as described in the Group R occupancy section - the IBC does not apply to 1&2 family dwellings or townhouses 3 stories or less.

    Which leads back to: Did NYS adopt a code based on the IRC? IF so, that would be the code which would be compared to the IRC and the NJ IRC changes.

    The NJ IRC takes the IRC and makes it less stringent.

    The NYS Building Code, at least the section you posted, remains basically as the IBC was (without making a word-for-word comparison between the two codes to find the differences).
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