Horizontal exits and H occupancy

[chris macko]

I've got a 2 story section of a building with H-3 occupancy on both floors. There's a 3-hour fire wall separating that part of the building from the rest, which is a much larger F-1 unlimited area building. When using the fire wall as a horizontal exit, is there any restriction on exiting to a higher hazard area (from F-1 to H-3)? I know that's not allowed for an exit access path, but I don't see anything prohibiting it in the horizontal exit section. That being said, it does not feel like it should be allowed, but the client on this job has shared some drawings from a previous project where it looks like that is what was done.

 

[TheCommish]

2015 IBC section 1016.2
2. Egress from a room or space shall not pass through
adjoining or intervening rooms or areas, except where
such adjoining rooms or areas and the area served are
accessory to one or the other, are not a Group H occupancy
and provide a discernible path of egress travel to
an exit.
Exception: Means of egress are not prohibited
through adjoining or intervening rooms or spaces in
a Group H, S or F occupancy where the adjoining or
intervening rooms or spaces are the same or a lesser
hazard occupancy group.

 

[RLGA]

@TheCommish, that is true for the exit access. However, a horizontal exit is not part of the exit access. Once an occupant has passed through a horizontal exit, they have effectively exited the other building.

Just out of curiosity, @chris macko, is the "unlimited area building" per Section 507.5, or is the Group F-1 in Type IA construction? If the former, why the need for a fire wall?

 

[TheCommish]

RLGA, you are correct

Still not a good method in my opinion, however who said the code makes sense

 

[chris macko]

@TheCommish, that is true for the exit access. However, a horizontal exit is not part of the exit access. Once an occupant has passed through a horizontal exit, they have effectively exited the other building.

Just out of curiosity, @chris macko, is the "unlimited area building" per Section 507.5, or is the Group F-1 in Type IA construction? If the former, why the need for a fire wall?

That was what I was thinking as well, thanks for confirming. I'm still going to try to avoid this condition if at all possible.
Yes, the unlimited area building is 2 story sprinklered per 507.5 (F-1 with B above), type IIB construction, and the other area is 3 stories (H-3, H-4, and F-1 with a mechanical floor above). The amount of H-3 and H-4 area was too large to be accessory to the F-1 and the building is 1.2 million sq feet total, so the firewall seemed like a better option than rating the entire structure. The issue now is the client wants to remove as many egress passageways as possible with a lot of large pieces of equipment that we have to work around, so I may need to add additional fire barriers to get some more horizontal exits.

 

[TheCommish]

Looking at section 507, does the condition comply with this code section, speaks to unlimited area buildings with H in it section 507.8 and limits to 10% of the floor area and 25% of the H on an exterior wall.

 

[chris macko]

A bit off topic, but the portion of the building with the large H-3/H-4 areas is not unlimited area, it is a type IB building following table 506.2. It's also 3 stories tall which doesn't work for unlimited area. There is a firewall to break it into 2 separate "buildings". The portion with the H occupancies is only about 20-25% overall and rating the entire building to IB would add a lot of cost/complexity.

 

[TheCommish]

Chris,

2015 IBC citations
It seems to me that you cannot have the unlimited budling for the F use, in this case because the unlimited building needs to have open space around is section 507.2, the H use is attached, therefor you do not have the open space around it.

 

[chris macko]

I agree that part does not meet the letter of the code, but since the overall building still has the 60ft open space, the AHJs here and in the past where this has come up have been amenable to it as a code mod.