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 R3188.8.131.52, 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 3184.108.40.206, 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 R3220.127.116.11, 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 318.104.22.168, 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.