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Spiral stairway width above handrail

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NH09

Silver Member
Joined
Sep 11, 2010
Messages
153
Location
New Hampshire
I have a homeowner who is planning to custom build a spiral stairway. I have given him a copy of section R311.7.9.1 and there are no issues aside from the width. He is planning to construct a "tube" due to limited space and will support the outside of the treads on cleats mounted to the wall. The code section states the minimum clear width at and below the handrail shall be 26", which leaves the question as to what the minimum width above the handrail should be. R311 states all stairways should have a minimum clear width of 36" above the handrails and the section pertaining to spiral stairways does not mention it at all - any thoughts?
 
The 2006 IRC does not make the distinction that the 2009 makes, concerning "at and below the handrail".

The 2006 version (R311.5.8.1) allows for the "tube" concept, with the tube being just large enough to contain two treads width and the width of the center support, with no additional consideration for the handrail. In other words, under the 2006, the hardrail can project into the required space.

I believe the intent of the revision is to ensure the handrail does not project into the required space.

This is my opinion, but I can certainly see, that because of the new wording, the exception may no longer apply to the space above the handrail.

Clear as mud.
 
I suppose that if the handrail is set at the 26" distance from the center of the stair case to the edge of the handrail, you will have the width of the rail, plus the distance of the required handrail clearance (1 1/2") added to the side of the "tube". That will add approx 3" to 4 1/2" to the 26" width. They will have anywhere from 29" to 30 1/2" (or more) at the width above the handrail.

However, it states in 311.7.9.1 that "all" the requirements of 311.7 apply except for the items mentioned in 311.7.9.1. If one were to require the minimum 36" above the handrail, that would mean you would have approx 10" on only one side of the width area above the handrail. That seems a bit lopsided to me.
 
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It does look like 311.7.9 is clear in stating "Spiral stairways and bulkhead enclosure stairways shall comply with all requirements of Section R311.7 except as specified below". By not mentioning height above the handrail there is no other choice but to fall back on section 311.7.1 -Stairway width. I told the homeowner if he wanted to go with a "tube" he could, but the width above the handrail, from the center support to the wall would need to be 36" minimum. Thanks Jobsaver and Glennman for your replies
 
not going to get furniture up and down easily.. I think a code modification would be necessary.. (and a code change required).
 
Good point Peach, I mentioned that to him and he said he was going to put a "trap door" in the second floor ceiling to move furniture in (can't wait to see the plans for that). It seems to me it would be a heck of a lot easier to find a way to get some code compliant stairs in.
 
NH09,

You had it right in your posting, there is no change in the width above handrail height only the width below handrail height.

So the wall tube has to be 36" radius plus half the diameter of the center support at its widest point. I say half the distance of the center support at it's widest because the code does not require a center support to be round.

On a second note forget about the spiral being built in place and rather just think of it as being installed in a wall opening you would still require the stair width clearance from center also.

The 36" width is measured from edge of center support to wall.
 
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peach said:
not going to get furniture up and down easily.. I think a code modification would be necessary.. (and a code change required).
Click to expand...
Ikea is easier than code modifications.
 
NH09 - "It seems to me it would be a heck of a lot easier to find a way to get some code compliant stairs in."

A properly designed spiral stair IS a code compliant stair...
 
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