Scissor stair

[sergoodo]

I have seen some buildings with requirements for 2 exits on an upper floor use a cooridor to establish minimum door placement distance for the 2 entries of the (1) scissor stair exit.

these floors do not meet the 2 exit requirement of 2015 IBC without an additional exit stair.

What am I missing?

 

[cda]

Interesting, have not seen that one.

Maybe

1. someone talked the bo into accepting it.

2. since you have the exit separation, once you are in the corridor or in the enclosure, you are considered outside the building.
Only trouble with that one is if that enclosure gets compromised, such as full of smoke??

 

[sergoodo]

I am just looking @ code and so far...no way for scissor stairs to meet compliance for 2 exits. I will double check what I think I 'seen'

 

[fatboy]

I agree, they do not comply.........you need the separation.

 

[sergoodo]

residential tower with 2 exits via scissor stair

 

[cda]

residential tower with 2 exits via scissor stair

LOOKS good on separation,,,,


But if the enclosure is full of smoke, than what???


Sounds like someone sold them that it was ok, and was accepted??????


HOW many stories??

 

[fatboy]

1007.1.1 Two exits or exit access doorways. Where two

exits, exit access doorways, exit access stairways or

ramps, or any combination thereof, are required from any

portion of the exit access, they shall be placed a distance


apart equal to not less than one-half of the length of the

maximum overall diagonal dimension of the building or

area to be served measured in a straight line between them.

Interlocking or scissor stairways shall be counted as one


exit stairway.

 

[Inspector Gift]

This was an interesting question. Google had many examples. Both of these were used in comments stating they meet the code separation.

Fire-rated separation is not clear from the original posters question (or in these examples), But in order for them to meet the code requirements there needs to be a fire-resistance rated separation between them.

 

[cda]

View attachment 2724 View attachment 2725
This was an interesting question. Google had many examples. Both of these were used in comments stating they meet the code separation.

Fire-rated separation is not clear from the original posters question (or in these examples), But in order for them to meet the code requirements there needs to be a fire-resistance rated separation between them.

Or another set somewhere else in the building

 

[steveray]

Seems like remoteness would be an issue, at the entrance and possibly the discharge...If they share the enclosure (atmosphere), it is one exit IMO...

 

[cda]

Maybe the elevator was accepted as an exit??


Elevators as Accessible Means of Egress


Elevators required or provided as an accessible means of egress must comply with requirements in IBC Section 1007.4. To be considered an accessible means of egress, elevators must be provided with standby power in accordance with NFPA 110, Emergency and Standby Power Systems, or NFPA 111, Stored Electrical Energy Emergency and Standby Power Systems. NFPA 110 provides requirements for generators, whereas NFPA 111 provides requirements for stored energy type systems, such as batteries.


As previously mentioned, elevator lobbies may serve as a required area of refuge for elevators used as an accessible means of egress. Elevators are not required to be accessed by an area of refuge when buildings are sprinklered throughout with a system complying with NFPA 13 or 13R, when elevators are not required to be enclosed in a shaft, and when elevators are accessed by a horizontal exit. If used as an area of refuge, elevator lobbies must be enclosed with smoke barriers and provided with two-way communication to the fire command center or other location approved by the fire department. Also, elevator lobbies used as areas of refuge must accommodate one 30- by 48-inch wheelchair space for every 200 occupants served by the area of refuge. The wheelchair spaces cannot reduce the required means of egress width.

http://www.specsandcodes.com/articles/code_corner/The Code Corner No. 38 - Elevators.pdf





Also


http://fire.nist.gov/bfrlpubs/fire07/PDF/f07054.pdf

 

[Paul Sweet]

Scissors stairs used to be common in some cities. They are supposed to be separated by a noncombustible wall. The reason they were banned (actually I think they were no longer allowed to be considered as 2 separate exits, but I can't find where that is hidden) is because it was almost impossible to seal the dividing wall adequately to prevent passage of smoke from one stair to the other.

 

[cda]

http://buildingcodenyc.com/sketches/distance-between-exit-doors/

 

[fatboy]

1007.1.1 Two exits or exit access doorways. Where two exits, exit access doorways, exit access stairways or ramps, or any combination thereof, are required from any portion of the exit access, they shall be placed a distance apart equal to not less than one-half of the length of the maximum overall diagonal dimension of the building or area to be served measured in a straight line between them. Interlocking or scissor stairways shall be counted as one exit stairway.

 

[sergoodo]

Fatboy do you interpret "Interlocking or scissor stairways shall be counted as one exit stairway" to equal "one exit" from a floor...therefore the residential tower plan posted is non compliant if 2 exits are required?

CDA, Do you interpret "Elevators as Accessible Means of Egress" to be a portion or component acceptable to access an exit...or considered an additional compliance like "area of refuge"?

 

[cda]

Fatboy do you interpret "Interlocking or scissor stairways shall be counted as one exit stairway" to equal "one exit" from a floor...therefore the residential tower plan posted is non compliant if 2 exits are required?

CDA, Do you interpret "Elevators as Accessible Means of Egress" to be a portion or component acceptable to access an exit...or considered an additional compliance like "area of refuge"?

Sorry beyond my limited code knowledge,


“”accessible means of egress, as defined by the IBC, is a “continuous and unobstructed way of egress travel from any point in a building or facility that provides an accessible route to an area of refuge, a horizontal exit, or a public way.” Where more than one means of egress is required from any accessible space, each accessible portion of the space must be served by at least two accessible means of egress. Accessible spaces can be served by one accessible means of egress only where the IBC permits one means of egress.”””

 

[steveray]

Scissor stair , one exit....One enclosure, one exit...The intent of remoteness is that it makes it hard to lose more than one required exit. If you had a fire that compromised that one enclosure, you would lose 2 exits (if it were allowed) No bueno....

 

[fatboy]

Fatboy do you interpret "Interlocking or scissor stairways shall be counted as one exit stairway" to equal "one exit" from a floor...therefore the residential tower plan posted is non compliant if 2 exits are required?QUOTE]


Yes, I think the section is quite clear, it is considered to be one exit. The plan exceeds 4 units, so a 2nd exit is required that meets the separation requirements.

 

[sergoodo]

cda's post got me thinking about the components of an "exit". Maybe each door is an exit to the floor and the 1 exit stairway is like an exit thru an adjacent building. Pass thru the door and you have exited the building.

 

[sergoodo]

Scissor stair exit interpretation currently varies by jurisdiction, currently looking into the ban debate which Paul Sweet brought up. I have read that this debate started after 911 realizing the ability to target scissor stair grouped exits. Goal would be to determine if the assemblies used to separate are functionally sound therefore safe, sans the smarmy terrorist factor.