Spiral Stair Opening

[Francis Vineyard]

It appears there should be 10 inches of clearance measured horizontal from the hand top rail where the stairs passes through the floor; in your opinion would 4½ inches fit this bill?

R311.7.1Width.

​

Stairways shall not be less than 36 inches 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 on either side of the stairway and the minimum clear width of the stairway at and below the handrail height, includingtreads and landings, shall not be less than 311/2 inches where a handrail is installed on one side and 27 inches where handrails are provided on both sides.

​

Exception:

​

The width of spiral stairways shall be inaccordance with Section R311.7.9.1.

​

R311.7.2 Headroom.

​

The minimum headroom in all partsof the stairway shall not be less than 6 feet 8 inches measured vertically from the sloped line adjoining the tread nosing or from the floor surface of the landing or platform on that portion of the stairway.

​

Exception:

​

Where the nosings of treads at the side of a flight extend under the edge of a floor opening through which the stair passes, the floor opening shall be allowed to project horizontally into the required headroom a maximum of 43/4 inches.



​

 

[Yankee]

have a sketch?

 

[tbz]

It appears there should be 10 inches of clearance measured horizontal from the hand top rail where the stairs passes through the floor; in your opinion would 4½ inches fit this bill?

R311.7.1Width.

​

Stairways shall not be less than 36 inches 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 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 where a handrail is installed on one side and 27 inches where handrails are provided on both sides.

​

Exception:

​

The width of spiral stairways shall be inaccordance with Section R311.7.9.1.

​

R311.7.2 Headroom.

​

The minimum headroom in all partsof the stairway shall not be less than 6 feet 8 inches measured vertically from the sloped line adjoining the tread nosing or from the floor surface of the landing or platform on that portion of the stairway.

​

Exception:

​

Where the nosings of treads at the side of a flight extend under the edge of a floor opening through which the stair passes, the floor opening shall be allowed to project horizontally into the required headroom a maximum of 43/4 inches.



​

R311.7.9.1 Spiral stairways. Spiral stairways are permitted, provided the minimum clear width at and below the handrail shall be 26 inches (660 mm) with each tread having a 71/2-inch (190 mm) minimum tread depth at 12 inches (914 mm) from the narrower edge. All treads shall be identical, and the rise shall be no more than 91/2 inches (241 mm). A minimum headroom of 6 feet 6 inches (1982 mm) shall be provided.

Francis,

Handrail clearance from the outside handrail edge to the wall of the floor opening is Min 1.5", it can be larger, just not smaller,

the 4.5" measurement is based on if the stairway has walls(or guard frames or other) on both sides from the floor to a min of 84" above the nosing line lets say.

With a total width of 36", the handrails would then project inward, thus reducing the width of the stairway at the handrail height, thus a maximum encroachment of 4.5" is only allowed, but the 1.5" clearance on the outer side is still required.

Since the handrail encroaches in, the code figures your basically not using the space under the handrail to walk on, thus they allow the area under the handrails to be reduced also, as long as, that item is sitting under a handrail.

If the outer edges of the handrails are further a part than 36", on the top of the handrails, the 1.5" clearance rule still applies and thus I am not sure were you are pulling the 10" figure from.

 

[Francis Vineyard]

Tom,

Thanks for the explanations.

Is it correct to interpret that the 36 inch minimum clearance above the handrail; hence 10 inches wider than the spiral stairs is a design to permit passage of appliances and furniture and not necessary should there be another compliant means of egress from the other stories?

Yankee it's a 5 ft. diameter stair through a 5' 9" opening in the middle of the floor.

 

[tbz]

Francis,My understanding of the clearance for spirals is as follows."R311.7.1Width.Stairways shall not be less than 36 inches 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 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 where a handrail is installed on one side and 27 inches where handrails are provided on both sides.Exception:The width of spiral stairways shall be in accordance with Section R311.7.9.1."Stairways require 36" width above handrails EXCEPT SPIRALS, the exception refers you to R311.7.9.1

R311.7.9.1 Spiral stairways. Spiral stairways are permitted, provided the minimum clear width at and below the handrail shall be 26 inches (660 mm) with each tread having a 71/2-inch (190 mm) minimum tread depth at 12 inches (914 mm) from the narrower edge. All treads shall be identical, and the rise shall be no more than 91/2 inches (241 mm). A minimum headroom of 6 feet 6 inches (1982 mm) shall be provided.Francis,

In R311.7.9.1The clearance is based on between the center pole and the inside edge of the handrail can't be less than 26"Therefore, if your overall spiral stairway width to the outside edges of the handrail is 60" ( 5ft ) and the inside dimension from the inside edge of the handrail to the pole is 26" or more than the opening need only by 63" in width.60" overall spiral width, plus 1.5" on both sides = 63" 60" + 1.5" + 1.5" = 63"

If I am understanding your question correctly.TomView attachment 498

View attachment 498

/monthly_2011_11/francisspiral.jpg.3175412f014a8b2f3b132d8b21d1d795.jpg

 

[tbz]

Francis,

If the required width for spirals is held to the 36" requirement above handrail height, then all spirals under 6ft in diameter would be required to have 72" diameter + the pole diameter minimum in the floors period.

 

[Francis Vineyard]

Francis,If the required width for spirals is held to the 36" requirement above handrail height, then all spirals under 6ft in diameter would be required to have 72" diameter + the pole diameter minimum in the floors period.

True,

Usually I haven't questioned this section before because these stairs have had the 36 inch width above the handrails where installed; so I am checking here for others interpretations.

 

[gbhammer]

We rarely see spiral stairs around here, maybe one or two a year.

How often do the rest of you see them?

 

[brudgers]

We rarely see spiral stairs around here, maybe one or two a year. How often do the rest of you see them?

several times a day...spiral stairs lead to my office.

 

[gbhammer]

several times a day...spiral stairs lead to my office.

No wonder your so dizzy.