Spiral stairs in residential means of egress

[Sifu]

Reading the code and commentary for spiral stairs and once again at a crossroads. R311.5.1 and commentary requires 36" for stairs, with exceptions for spirals......the commentary for this section then reads that the 3 elements of MOE are required to be 36". Move to 311.5.8.1 and commentary for spirals. Code gives the required dimensions, commentary goes on to read that spirals that meet the code:

"A spiral stairway that meets

these requirements may provide the only means of

egress from a level regardless of the occupant load or

size of area served."

I know commentary isn't enforced. But it does help form decisions. One commentary tells me MOE must be 36", the next tells me spirals are OK even when less than 36". Code is silent.

Looks to me like MOE is required to be 36" for stairs with the exception for spirals, therefore they would be allowed as long as they meet 311.5.8.1.

Anybody run up against this, what has been allowed and why?

 

[mtlogcabin]

2009 IRC

R311.7.1 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 311/2 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.

R311.7.9.1 Spiral stairways.

Spiral stairways are permitted, provided the minimum clear width at and below the handrail shall be 26 inches

It looks like it is only a one inch difference

 

[codeworks]

according to r311.5.8 spirals may be 26" in width. the code is full of exceptions, this is one of those deals. residential occupancies do not usually have an excessive occupant load, one must be able to build ones domain as one wishes, codes are here to (unfortunately sometimes) "protect us from ourselves", someone may take issue with that, however, it is true with many laws today. if a spiral stairway meets the full intent of r311.5.8 and r311.5.8.1 the stairs should be considered as code compliant, IMO, good luck we're in 2006 irc

 

[JBI]

Must meet all req's of R311.9.1 in order to comply.

 

[Francis Vineyard]

Robert S,

I recently posted a similar question on this section and where it didn't comply in a design was the 36" of clearance above the handrails intruded by the floor/ceiling assembly. IMO the exception only for the width at and below the handrails as mtlogcabin so aptly highlighted in his answer.

Francis

 

[tbz]

Thread Francis is referencing

http://www.inspectpa.com/forum/showthread.php?6896-Spiral-Stair-Opening&highlight=spiral

 

[steveray]

Take the stairs out and put in a fire pole....maybe it has changed in the newer codes, but my 03 based stuff only "requires" the exit door....you don't need interior stairs, or doors, in fact where does it prevent you from having an 18" cased opening into a room? Chasing MOE in SFD as long as you have EERO is pretty tough from a code standpoint IMHO...

 

[codeworks]

jbi, what year irc are you refering to, i posted 2006, 311.9 is non existant in the 2006

 

[Sifu]

It looks like most have come to the same conclusion as me. Spirals permitted as long as they meet the requirements. I had never run into it before and now I have. Learn something new everyday, which is easy with such a short memory!

 

[brudgers]

Take the stairs out and put in a fire pole....maybe it has changed in the newer codes, but my 03 based stuff only "requires" the exit door....you don't need interior stairs, or doors, in fact where does it prevent you from having an 18" cased opening into a room? Chasing MOE in SFD as long as you have EERO is pretty tough from a code standpoint IMHO...

Within a dwelling, what matters is means of escape, not means of egress - hence the EERO. NFPA101 gets this, the IBC doesn't and hence there is confusion.

 

[brudgers]

Spiral stairs in dwellings tend to limit the occupant load of the area they exclusively serve.

 

[peach]

you are probably not going to find a manufactured spiral staircase with less than a 4.6' diameter. That leaves approximately 27" for the tread (I don't know that I've seen a handrail on a spiral stair at anyplace but the top rail of the stair). Curious why with all other stairs, the width is measured at all points above the handrail height.