IBC Means of Egress Sizing

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    David Kaplan

    Adelina,

    Here's my input:

    1) No, stairs do NOT have an ultimate width.  However, once you get to a certain width, you need to start introducing intermediate handrails into the design.  Code says that all portions of the required width must be within 30" of a handrail.  So, the maximum stair width you can have without an intermediate handrail would be 5'-0".  Once you exceed that, an intermediate railing needs to be looked into.

    2) 1005.3.2 applies to all egress components OTHER THAN stairs.  So yes, corridors, passageways, doors, etc.  Keep in mind of course, as you've correctly cited in your #3, that corridor width is also governed elsewhere in the code.

    3) I'm actually little stumped here but my gut is telling me that the door width does not need to be 44" clear because the code specifically allows you to size a door using the calculation.  The other thing I'd point out is that it also depends on the floor plan layout.  If you truly have a corridor leading to a door, with no other path of travel available (i.e. a common path of travel), then I could see the door width needing to match the required corridor width.  But even then I gotta tell you, I feel like the Code does not require that.  In other scenarios, where a corridor can be traveled in two different directions to two different doors, the occupant load at each door would be split up, so there you'd probably end up with less people at the door.

    Others should chime in.  I feel good about items 1 and 2 though.

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    Adelina Koleva

    David, thank you so much for replying! It is very helpful that you've confirmed this, thank you. I've just looked at the IBC again and I think you might be right, in that this could be controlled by the requirements for the number of exits :) Thanks again!

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    Seth Wiley

    I don't have the code excerpts in from of me but egress door sizing needs to take into account tributary loads (like floors above) so they typically don't get SMALLER but rather BIGGER as one proceeds toward the exit/exit discharge. Accessibility also typically needs to be part of the analysis so 32" min clear would mean 34" or 36" door, etc. etc. And of course multiple means of egress as well as things like 50% of occupancy needing to fit through main / front entry/exi will affeect the calculations.

    Building Codes Illustrated does a good job of explaining this including good diagrams.

    Hope that's helpful.

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    Adelina Koleva

    Thanks Seth! BCI has been very helpful, I'll have a look at it again.

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