Internal Stairs question
Wondering if anyone knows what the minimum width dimensions would be for internal staircase? Connecting two floors to create a duplex and would like to avoid a spiral stair if possible. Any info would be appreciated. TIA!
Wondering if anyone knows what the minimum width dimensions would be for internal staircase? Connecting two floors to create a duplex and would like to avoid a spiral stair if possible. Any info would be appreciated. TIA!
Thank you all so much! This would be a secondary stair and we would not be removing the existing stairs or doors for exit & entry. I want it to be comfortable to use but narrow enough to save as much space as possible. I am thinking 30″ would be ideal. thanks again!
if you are leaving both existing entry doors and the stair is purely for “convenience” then there are no code restrictions on dimensions(up until the end of this month anyway). I think you should use the conventional handrail dimensions and riser/run formulas as a starting point. Daves right 3’0″ is generally a good startign point. Minimum width of 24″ is as tight as it could be in my opinion.
-jp
Again, depending upon some other issues like how many stories in the building, you might be able to do 30″ or 33″ if both floors have separate exists. This is common when combining two floors of a row house. You would need to leave both existing doors to the main stair.
It’s not entirely cut and dry, but here’s the 1968 code:
§[C26-604.8] 27-375 Interior stairs. – Interior stairs shall comply with the following requirements:
(a) Capacity. –
(b) Width. – The width of interior stairs shall be the clear width between walls, grilles, guards, or newel posts.
Stair stringers may project into the required width not more than two inches on each side of the stair. No interior
stair shall be reduced in width in the direction of exit travel. Interior stairs shall be at least forty-four inches wide
except as follows:
(1) Interior stairs may be not less than thirty-six inches wide when serving not more than thirty occupants per stair
on any floor in buildings classified in occupancy groups J-1 and J-2, or when serving buildings classified in
occupancy group J-3 and exceeding four stories in height, or when serving not more than sixty occupants per stair
on any floor in buildings classified in occupancy groups E, B, and D.
(2) Interior stairs may be not less than thirty inches wide when serving mezzanines having an occupant load not
exceeding twenty-five persons or when located in buildings classified in occupancy group J-3 not more than three
stories in height. Interior stairs in four story buildings classified in occupancy group J-3 shall be a minimum of
thirty-three inches in width.
Jim Hill, RA, LEED AP
It depends on the code in any particular city. Most of them, for newly constructed stairs, are 3 feet. There are also codes that apply to the railings as well.