Horizontal Exits- 2006 IBC

[SAT]

IBC 2006 – Auditorium building Type I B construction one story with three mezzanine levels. To comply with egress requirements for exit width the designer is proposing a horizontal exit on the third mezzanine level(two other vertical exits are provided). Horizontal exit is being established by a 2 hour rated corridor as the fire compartment with exits one on each side of the long corridor. One vertical exit stair 2 hour rating enclosure is leading to outside and the second is 1 hour rated enclosure leading into the lobby area which leads to the outside.

My question is when the corridor is used as the fire compartment/ horizontal exit I am finding it challenging to calculate number of exits and exit width since we can not count the occupant exiting through the horizontal exit. I can use dead end corridor to establish exit on each side of corridor the question then is would the second stairs exiting through lobby complies? I do understand that the horizontal exit is an area of refuge what factor would we use to establish minimum area required for this area of refuge I am reading 3 square feet per occupant.

One more question Section 1022.2 Separation states below the exception “Horizontal exit walls constructed as fire barriers shall be continuous from exterior wall to exterior wall so as to divide completely the floor served by the horizontal exit.” I read this as part of the requirement however placement under the exception makes the language more part of the exception???

Any help or comments are appreciated ideas??

 

[cda]

with out a plan to look at a little hard to make a call,

BUT does not sound like you have a true horizontal exit,

and a few other things about the set up do not sound right

 

[mtlogcabin]

I am also having a hard time visualizing a mezzanine having a true horizontal exit. Can you attach a for plan?

EXIT, HORIZONTAL. A path of egress travel from one building to an area in another building on approximately the same level, or a path of egress travel through or around a wall or partition to an area on approximately the same level in the same building, which affords safety from fire and smoke from the area of incidence and areas communicating therewith.

 

[cda]

not sure if you can do an exit pasageway???

 

[SAT]

I tried to upload the floor plan but was unable to, due to size of file.

Thank you all for input.

 

[brudgers]

IBC 2006 – Auditorium building Type I B construction one story with three mezzanine levels. To comply with egress requirements for exit width the designer is proposing a horizontal exit on the third mezzanine level(two other vertical exits are provided). Horizontal exit is being established by a 2 hour rated corridor as the fire compartment with exits one on each side of the long corridor. One vertical exit stair 2 hour rating enclosure is leading to outside and the second is 1 hour rated enclosure leading into the lobby area which leads to the outside. My question is when the corridor is used as the fire compartment/ horizontal exit I am finding it challenging to calculate number of exits and exit width since we can not count the occupant exiting through the horizontal exit. I can use dead end corridor to establish exit on each side of corridor the question then is would the second stairs exiting through lobby complies? I do understand that the horizontal exit is an area of refuge what factor would we use to establish minimum area required for this area of refuge I am reading 3 square feet per occupant.

One more question Section 1022.2 Separation states below the exception “Horizontal exit walls constructed as fire barriers shall be continuous from exterior wall to exterior wall so as to divide completely the floor served by the horizontal exit.” I read this as part of the requirement however placement under the exception makes the language more part of the exception???

Any help or comments are appreciated ideas??

Typically, occupant load would be based on the number of seats/standing/stage. The required capacity of egress elements would be based upon the portion of those occupants served.

In the case of a true horizontal exit. The occupant load of the other building or fire area would not come into play for determining egress capacity. Based on experience, those occupants will not be inclined to enter the adjacent burning building or fire area.

 

[cda]

SAT

hand draw a simple sketch

 

[Examiner]

I would like to see that one also. Mezzanine being used as a horz exit.

 

[steveray]

Is the supporting construction Rated? Just Askin?

 

[Builder Bob]

Type I B construction meets the criteria for allowing an hortizontal exit that would not have to extend vertically thru the building, but could be sectioned off on one floor. I do however have a problem with a two hour corridor and reducing a stairway to one hour..... One of the basic premises of means of egress is that one a level of protection is achieved, it shall be maintained to the exit discharge. I don't think 707 would allow that: Shaft enclosures shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.

The horizontal exit separation shall extend vertically through all levels of the building unless floor assemblies have a fire-resistence rating of not less than 2 hours with no unprotected openings.

 

[texasbo]

Sec. 1022.4, 2006 IBC says that the capacity of the refuge area shall be adequate to accomodate the original occupant load of the refuge area, plus the occupant load from the adjoining compartment. The occupant load from the adjoining compartment shall be based on the capacity of the horizontal exit doors, and your reading of 3 square feet per person in the refuge area is correct. You are also correct in the statement that the exits from the refuge area are not required to be designed to accomodate the added capacity that comes through the horizontal exit (1022.1)

Neither Sec. 505, nor1020 prohibit the 1 hour stair enclosure; in fact it could be nonrated. 1020.1 states that mezzanines need not be included in the number of stories an exit enclosure serves, and exception 9 allows unenclosed stairways.

Type IB construction requires 2 hour floor construction, therefore the horizontal exit could be a fire barrier that does not extend vertically through all parts of the building per 1022.2.

Floor plan would help.