The National Building Code has Specific Requirements for Stair Treads and Risers
By Mark J. Donovan
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When building a home or home addition that includes stairs, it is important that they are built to the National Building Code (NBC), and/or your local building code requirements. In 1993 the NBC updated the requirements for stair treads and risers.
Stair Treads and Noses The NBC currently states that stair treads must have a minimum depth of 9”. In addition the nose of the stair tread cannot extend out more than 1” from the stair riser. |
By having a minimum stair tread depth requirement of 9”, the NBC believes that there is sufficient surface area for a person to safely step on it. Also, by limiting the nose length to a maximum of 1” they believe that there is less likelihood of a person accidentally getting a toe caught on the stair tread edge and tripping. Stair treads wider than 9” are allowed.
| Stair Risers
In regards to stair risers, the NBC specifies a maximum height of 8 ¼”. By capping the stair riser height at 8 ¼” the NBC believes that the disabled or elderly should be more capable of managing the staircase when climbing it. Note that this is a maximum height requirement on the stair riser. Shallower step risers are allowed, and when used in conjunction with wider stair treads, they can produce a set of stairs that offer a touch of elegance as well as increased functionality. |
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Stair Tread Width Requirements (Clear Width)
In residential building the NBC and most local building codes require stairs to be a minimum of 36” wide to allow two people to simultaneously ascend or descend them. This requirement is referred to in the building industry as the “Clear Width”.
| Stair Headroom Height Requirements
In addition to stair treads and riser requirements the NBC also states that the minimum stair height to be maintained is 80” (6’ 8”). This height needs to be maintained throughout the entire length of the stairway. Floating Steps and Spiral Stair Cases Floating steps, and in many cases spiral stair cases, have no visible riser, however they too must meet the same 8 ¼”stair riser requirement per the NBC. In regards to the stair tread depth, they are allowed some flexibility, however in general they typically need to meet a standard depth approximately 12-14 inches in from the narrow side. |
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So before you start cutting your stair stringers make sure you follow the NBO and your local building code requirements for stair treads and risers.
For more help on building a home addition, see HomeAdditionPlus.com’s Home Addition Bid Sheets. Our Home Addition Bid Sheets provide you with the knowledge and information on how to plan a home building project, and what to look for when hiring contractors. They also include detailed cost breakdown tables and spreadsheets for estimating your own new home construction building costs.
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