There's no code requirement to have a stair wider than 4'-2" in a two-stair office building with voice alarm.

[nealderidder]

Forget for a minute that there may be other reasons for a wider stair, we're considering only code requirements for this thought exercise. CBC in my case. Think of a generic office building with multiple levels, including high-rises, but not anything tall enough to trigger a third stair per CBC 403.5.2

For a building with two interior exit stairs the largest occupant load than can be served is 500 per floor (CBC Table 1006.3.2). Let's also install a voice alarm per 907.5.2.2 in our imaginary building. And we're sprinkled.

500 occupants x .2" capacity factor = 100"
100"/2(stairs) = 50" per stair

1011.2 requires a minimum stair width of 44" - Got that.
1009.3.2 requires 48" between handrails but only if not sprinkled so it doesn't apply.


So I don't see anything that would require me to provide a stair (x2) wider than 50" in a 20 story office building with 50,000 SF floor plates (just to give a specific example). Am I missing anything? Is there anything in the code that would push these stairs wider than 50"?

 

[north star]

# # = # #

Are the planned stairways intended to be used
in an emergency, for emergency response personnel
going up while the bldg. occupants are exiting down
[ i.e. - simultaneous use ] ?

( & & & )

 

[RLGA]

Forget for a minute that there may be other reasons for a wider stair, we're considering only code requirements for this thought exercise. CBC in my case. Think of a generic office building with multiple levels, including high-rises, but not anything tall enough to trigger a third stair per CBC 403.5.2

For a building with two interior exit stairs the largest occupant load than can be served is 500 per floor (CBC Table 1006.3.2). Let's also install a voice alarm per 907.5.2.2 in our imaginary building. And we're sprinkled.

500 occupants x .2" capacity factor = 100"
100"/2(stairs) = 50" per stair

1011.2 requires a minimum stair width of 44" - Got that.
1009.3.2 requires 48" between handrails but only if not sprinkled so it doesn't apply.


So I don't see anything that would require me to provide a stair (x2) wider than 50" in a 20 story office building with 50,000 SF floor plates (just to give a specific example). Am I missing anything? Is there anything in the code that would push these stairs wider than 50"?

I think you have the gist of it per the IBC.

However, if you have to comply with NFPA 101, too, the stairs will have to be wider (at least 56 inches) if the cumulative occupant load in the stairway is 2000 or more. Thus, using your hypothetical building, you would need to widen your stairs to 56 inches at the 12th story.

 

[nealderidder]

# # = # #

Are the planned stairways intended to be used
in an emergency, for emergency response personnel
going up while the bldg. occupants are exiting down
[ i.e. - simultaneous use ] ?

( & & & )

Yes, I think you would have to assume that for any exit stairway.

 

[nealderidder]

I think you have the gist of it per the IBC.

However, if you have to comply with NFPA 101, too, the stairs will have to be wider (at least 56 inches) if the cumulative occupant load in the stairway is 2000 or more. Thus, using your hypothetical building, you would need to widen your stairs to 56 inches at the 12th story.

Thanks for the reply Ron. I believe the NFPA 101 has to be explicitly adopted by a jurisdiction, correct? Meaning that it isn't adopted "By reference" simply by adopting a version of the IBC/CBC as I believe is the case with NFPA 13, 72 etc.

 

[north star]

@ ~ @

" I believe the NFPA 101 has to be explicitly adopted by a jurisdiction, correct? Meaning that it isn't adopted "By reference" simply by adopting a version of the IBC/CBC as I believe is the case with NFPA 13, 72 etc. "

Yes !

@ ~ @

 

[RLGA]

Thanks for the reply Ron. I believe the NFPA 101 has to be explicitly adopted by a jurisdiction, correct? Meaning that it isn't adopted "By reference" simply by adopting a version of the IBC/CBC as I believe is the case with NFPA 13, 72 etc.

Correct. There is no reference to NFPA 101 in the IBC, so it must be specifically adopted. However, any healthcare project subject to Joint Commission accreditation and any project in Louisiana (I am sure there are others) will need to comply with NFPA 101 and the locally adopted IBC version since NFPA 101 is specifically adopted by those entities.