Do I need a stair in between each fire wall? Or can they egress through it?

[eyan50495]

Working on a long/large 4 story residential building. Due to its size and what construction type we want to achieve, we have to 'break the building down' into smaller fire areas with fire walls creating 'separate and distinct' buildings.

Currently, at each fire wall, both 'buildings' share a common stair and have access from each side. Someone proposed adding more fire walls to lower the construction type to save money and introduce more fire walls further subdividing the building.

However, due to space, we cannot add any more stairs and they are saying that due to IBC NYS 1026.1 Horizontal Exits, we do not need to add a stair at the new fire walls because occupants can exit through the fire wall into the adjacent 'building' as 50% of the exits are allowed to be horizontal exits.

Thoughts?

 

[Jay Smith]

Working on a long/large 4 story residential building. Due to its size and what construction type we want to achieve, we have to 'break the building down' into smaller fire areas with fire walls creating 'separate and distinct' buildings.

Currently, at each fire wall, both 'buildings' share a common stair and have access from each side. Someone proposed adding more fire walls to lower the construction type to save money and introduce more fire walls further subdividing the building.

However, due to space, we cannot add any more stairs and they are saying that due to IBC NYS 1026.1 Horizontal Exits, we do not need to add a stair at the new fire walls because occupants can exit through the fire wall into the adjacent 'building' as 50% of the exits are allowed to be horizontal exits.

Thoughts?

The way it would normally work is a story would have a stair at or near each end of the long building. The fire wall divides the building into two and the exit path goes through the fire wall in both directions. The fire doors become a horizontal exit if you need it to be because of travel distance, occupant load, or as an accessible means of egress. On each side, the occupants have access to a stair and a horizontal exit.

 

[RLGA]

@eyan50495, the application you described would be permitted.

Fire walls can be horizontal exits, but they do not have to be. Just because you added a fire wall does not mean you now have to comply with the requirements for horizontal exits. As @Jay Smith pointed out, you use horizontal exits to reduce travel distance or for accessibility reasons. You can also use horizontal exits to reduce the number of vertical exits (i.e., stairways and ramps).

 

[MKolchins]

Working on a long/large 4 story residential building. Due to its size and what construction type we want to achieve, we have to 'break the building down' into smaller fire areas with fire walls creating 'separate and distinct' buildings.

Currently, at each fire wall, both 'buildings' share a common stair and have access from each side. Someone proposed adding more fire walls to lower the construction type to save money and introduce more fire walls further subdividing the building.

However, due to space, we cannot add any more stairs and they are saying that due to IBC NYS 1026.1 Horizontal Exits, we do not need to add a stair at the new fire walls because occupants can exit through the fire wall into the adjacent 'building' as 50% of the exits are allowed to be horizontal exits.

Thoughts?

If you are trying to create separate buildings then "Fire Walls" are appropriate. Fire areas would be within a building and entail a different type of rated wall depending on why you are creating the fire area.

I haven't used fire walls in a while but it sounds like you have two fire walls with space for a common stair system between them. I recall provisions for exiting through the fire walls that create separate building from one building to the other so you should be able to exit each building through a common exit stair accessed through the fire wall on each side for each building. It sound like both buildings will be the same use group so I think if you design the stair to comply to the exit stair requirements for the intended use and it can handle the occupant load from both buildings simultaneously it should be compliant. If you had different uses you probably need to make sure the exit stair complied to the most restrictive use requirements.

You would use a horizontal exit if the stair discharged inside one of the buildings. As long as the stair discharges to a public way outside of the building you shouldn't need a horizontal exit. The horizontal exit extends the rated stair enclosure at the level of exit discharge until you get to the exit discharge (outside to public way).

 

[RLGA]

You would use a horizontal exit if the stair discharged inside one of the buildings. As long as the stair discharges to a public way outside of the building you shouldn't need a horizontal exit. The horizontal exit extends the rated stair enclosure at the level of exit discharge until you get to the exit discharge (outside to public way).

You are confusing horizontal exits with exit passageways.

 

[MKolchins]

You are confusing horizontal exits with exit passageways.

Long time since I dealt with Separate Buildings and I don't think I ever actually had to incorporate a horizontal exit. Taking a quick look you are correct although it seems like they are similar concepts meant to extend the exit. I spent the most time on these concepts back in the old BOCA days so my recollection is skewed toward the concepts under the BOCA Code. That said your earlier reply stated a horizontal exit is not required for a for a Fire Wall so it appears my basic premise that as long as the stair complies to the requirements for an exit stair for the intended Use(s) and can handle the occupant load from both buildings it should be compliant.

 

[RLGA]

Long time since I dealt with Separate Buildings and I don't think I ever actually had to incorporate a horizontal exit. Taking a quick look you are correct although it seems like they are similar concepts meant to extend the exit. I spent the most time on these concepts back in the old BOCA days so my recollection is skewed toward the concepts under the BOCA Code. That said your earlier reply stated a horizontal exit is not required for a for a Fire Wall so it appears my basic premise that as long as the stair complies to the requirements for an exit stair for the intended Use(s) and can handle the occupant load from both buildings it should be compliant.

Horizontal exits do not extend an exit, they just help reduce the distance to an exit if all exit enclosures exceed the prescribed travel distance. Once occupants pass through a horizontal exit, they are no longer within an exit--they are within a refuge area that theoretically bides them additional time until they reach an exit enclosure that leads to the exit discharge.

 

[steveray]

Ron has the more technical answer....50% is the key if you need them...Depending on how crazy you want to get on building vs. structure per IBC 1001.1 that is.....


1001.1 General. Buildings or portions thereof shall be provided
with a means of egress system as required by this chapter.
The provisions of this chapter shall control the design,
construction and arrangement of means of egress components
required to provide an approved means of egress from structures
and portions thereof.

706.1 General. Each portion of a building separated by one
or more fire walls that comply with the provisions of this section
shall be considered a separate building.

 

[Jay Smith]

Although the original post doesn’t exactly say this, I get the impression the real question being asked is simply whether a portion of the building between two fire walls requires its own complete egress system. Can one portion of the building utilize the exits on the other sides of the fire walls? We have established it can.

In addition to that, we have the reference to horizontal exits, which in my experience are often associated with fire walls as if a fire wall is a horizontal exit regardless of whether we want it to be. We often don‘t want it to be, because then we could not have an area with two fire walls and only one stair. Horizontal exits would be greater than 50% of the exits. That scenario often occurs in a donut plan divided in half, or the middle portion in a building divided in three.

This idea of a fire wall being by default a horizontal exit is a discussion I’ve seen come up many times. City of Houston once issued an official interpretation that a fire wall is a horizontal exit if you use it for allowable area purposes. My contention on a project there was that 503.1 says the portions separated by fire walls are considered to be separate buildings for purposes of determining area limitations, height limitations and construction type. That’s the intended full extent to which these areas are considered to be separate buildings. I got mine approved, but I don’t think it affected their interpretation going forward.

 

[Tim Mailloux]

Keep in mind that firewalls can be very expensive to build as they have to be structurally independent. I would have an estimator run some numbers on the cost of these firewalls compared to increasing the construction type.

 

[Genduct]

Working on a long/large 4 story residential building. Due to its size and what construction type we want to achieve, we have to 'break the building down' into smaller fire areas with fire walls creating 'separate and distinct' buildings.

Currently, at each fire wall, both 'buildings' share a common stair and have access from each side. Someone proposed adding more fire walls to lower the construction type to save money and introduce more fire walls further subdividing the building.

However, due to space, we cannot add any more stairs and they are saying that due to IBC NYS 1026.1 Horizontal Exits, we do not need to add a stair at the new fire walls because occupants can exit through the fire wall into the adjacent 'building' as 50% of the exits are allowed to be horizontal exits.

Thoughts?

Is it REALLY A FIRE WALL? Is the structure really 2 seperate, self supporting structures?
Seems it is not just the idea that there is a 30" Parapet wall projecting above the roof.

If not a separate structure, then isn't this really describing a Fire Barrier with a parapet?

I am a little confused, Like to hear from those more experienced than me

 

[Jay Smith]

Is it REALLY A FIRE WALL? Is the structure really 2 seperate, self supporting structures?
Seems it is not just the idea that there is a 30" Parapet wall projecting above the roof.

If not a separate structure, then isn't this really describing a Fire Barrier with a parapet?

I am a little confused, Like to hear from those more experienced than me

In Type VA construction with NFPA 13R sprinkler systems you’re working with a table value of only 12,000 square feet allowable area per story. The average allowable area with frontage might be 15,000 square feet. The total area of a 4-story residential project in my area is often 300 apartments averaging 800 square feet, plus common areas. That’s probably 5 fire areas not counting the parking garage. They often make the units available in phases, so this can be a convenient way to separate those phases.

Most of these Type VA apartment buildings have separate loadbearing stud walls at each dwelling unit separation. The fire wall rating of 2 hours is achieved by setting shaft liner between the stud walls. It does not require extending the fire wall above the roof. In the corridors there are rated doors, usually on electromagnetic holdopens. Ideally, the fire wall just cuts across the building between aligned dwelling units. The fire wall might or might not be adjacent to a stairway.

 

[Genduct]

In Type VA construction with NFPA 13R sprinkler systems you’re working with a table value of only 12,000 square feet allowable area per story. The average allowable area with frontage might be 15,000 square feet. The total area of a 4-story residential project in my area is often 300 apartments averaging 800 square feet, plus common areas. That’s probably 5 fire areas not counting the parking garage. They often make the units available in phases, so this can be a convenient way to separate those phases.

Most of these Type VA apartment buildings have separate loadbearing stud walls at each dwelling unit separation. The fire wall rating of 2 hours is achieved by setting shaft liner between the stud walls. It does not require extending the fire wall above the roof. In the corridors there are rated doors, usually on electromagnetic holdopens. Ideally, the fire wall just cuts across the building between aligned dwelling units. The fire wall might or might not be adjacent to a stairway.

I like your Texas explanation!
Best, Mike