Stair Capacity & Center HR?

[tbz]

Good afternoon all,

Have a project we are bidding, the main issue I see is that the architect did not show handrail placements on the stairs, but did show capacity notations.

Here in lies my question the architect has noted 4 units of width, by my viewing the stairs are over 68" in width thus would not a center handrail be required, thus leaving only (2) 40" wide paths of travel, and is a 36"-40" stair width considered 2 units, fore which the (4) units is noted?

Guess my concern is (3) handrails required because of width of flight, do the notations work with 3 handrails or is it based on (2) handrails?

 

[Sifu]

Looks to me like if the required width is greater than 60" then yes an intermediate handrail would be required. Is this the only means of egress?

 

[Coug Dad]

228 persons time 0.30 inches of stair per person = 68.4 inches of required width. Stair is 86 inches wide. The center handrail is required unless they negotiated a reduced capacity allowance for the 26 inches that are too far from the handrail.

 

[tbz]

Looks to me like if the required width is greater than 60" then yes an intermediate handrail would be required. Is this the only means of egress?

Sifu,

I get the required width part, my question was on the stated method and the width?

 

[Coug Dad]

Basing the egress on "units" went out of the code many years ago. Plus, their "units" appear to be feet compared to the old code "units" of 22 inches.

 

[tbz]

228 persons time 0.30 inches of stair per person = 68.4 inches of required width. Stair is 86 inches wide. The center handrail is required unless they negotiated a reduced capacity allowance for the 26 inches that are too far from the handrail.

Coug Dad,

I can follow your math and thus the (2) 38" clear spans between (3) handrails works.

I am trying to wrap my head around " 4 units of width x 60 = 240 "

Were does the 4 units of width come from? Or should I say were in the code is a unit of width defined to a size?

Thanks

 

[Coug Dad]

Legacy codes had egress based upon either 22 inch units or feet. I am not sure what "unit" they are referencing. Current codes use inches per person.

 

[Builder Bob]

Stairs are allowed to be as wide as they want to be with only two handrails, unless the required egress width places people more than 30" from a handrail....

Therefore, 60" of stair width can handle 200 occupants with two handrails if not sprinkler- 2006 ed. IBC or 300 occupants with two handrails if sprinkler system is installed.

egress width required - 0.3 inches per person non-sprinkler (60/.3 = 200)

0.2 inches per person if sprinklered (60/.2 = 300)

The 2012 IBC may be different...

(Clarification on Coug Dad response......)

 

[gbhammer]

Stairs are allowed to be as wide as they want to be with only two handrails, unless the required egress width places people more than 30" from a handrail....Therefore, 60" of stair width can handle 200 occupants with two handrails if not sprinkler- 2006 ed. IBC or 300 occupants with two handrails if sprinkler system is installed.

egress width required - 0.3 inches per person non-sprinkler (60/.3 = 200)

0.2 inches per person if sprinklered (60/.2 = 300)

The 2012 IBC may be different...

(Clarification on Coug Dad response......)

I would agree with unless the natural path of travel is direct to the middle of the stair, then there needs to be a handrail in the middle.

 

[Sifu]

I am with everyone else. Sorry didn't quite follow your question at first. The 4 units threw me off so I conveniently ignored it. My calc's come up the same as coug dad and builder bob.

 

[Architect1281]

Weel any occupied stair width will give you 100 occupant exit capacity per handrail per 30 " the most a 7'-4" stair can handle with rails on EACH SIDE WOULD BE 200 OCCUPANTS - ONE RAIL IN THE MIDDLE OF A MILE WIDE STAIR = 200 OCCUPANTS

 

[Builder Bob]

Weel any occupied stair width will give you 100 occupant exit capacity per handrail per 30 " the most a 7'-4" stair can handle with rails on EACH SIDE WOULD BE 200 OCCUPANTS - ONE RAIL IN THE MIDDLE OF A MILE WIDE STAIR = 200 OCCUPANTS

Sorry, stairs in IBC require two handrails minimum........one on each side.