Fire Barriers

[Ktoby]

Back in the day when Fire Barriers were called Area Separation Walls, they could be used to separate different occupancies in the same building. Is that still the case? Example: Can a Fire Barrier be used to divide an R-2 Tri-plex into an R-3 one unit and an R-3 two unit. building?

 

[RLGA]

An area separation wall is more equivalent to the current fire wall than a fire barrier. Area separation walls were used to divide a larger building into two or more smaller buildings, but didn’t have quite the restrictions that fire walls have. Fire barriers are more equivalent to the occupancy separation walls. My response is based on the old UBC, with which I’m most familiar; I’m not familiar with the BOCA or SBCCI codes, which may have had slightly different applications for fire-resistant assemblies in their respective model codes.

 

[Ktoby]

An area separation wall are more equivalent to the current fire wall than a fire barrier. Area separation walls were used to divide a larger building into two or more smaller buildings, but didn’t have quite the restrictions that fire walls have. Fire barriers are more equivalent to the occupancy separation walls. My response is based on the old UBC, with which I’m most familiar; I’m not familiar with the BOCA or SBCCI codes, which may have had slightly different applications for fire-resistant assemblies in their respective model codes.

Yes you are right I used the wrong term. Thank you and I feel stupid now.
To follow, can I break up the triplex like I suggested in my initial question.

 

[walker.t]

can I break up the triplex like I suggested in my initial question.

Converting an existing wall into a fire wall would likely be, for all intents and purposes, technically infeasible. Fire walls have to be designed to allow the construction on either side of the wall to collapse yet for the wall to remain standing and continue to function as a fire wall (See IBC Chapter 2 definition of “fire wall”) - so anything that needs to bear on the fire wall will need to be designed to break away in a fire. There are also requirements for horizontal and vertical continuity of the firewall (706.5 and 706.6) which extend beyond the face of the wall or roof or require portions of the exterior enclosure to be rated. So it’s not just about adding several layers of wallboard to each side of the wall.

 

[steveray]

Your premise is sound, but why do you want to?

 

[RLGA]

The thing about fire walls is that their use is limited to the purposes of "determining area limitations, height limitations, and type of construction" for each portion of a building divided by fire walls. A fire wall is also permitted for creating separate buildings on separate lots as a party wall (no openings). For all other code applications, a fire-wall-separated building is still a single building.

That said, a fire wall could create two R-3 units for determining allowable area and height. However, as someone previously mentioned, why would you want to do that? If they are three connected dwelling units, each with its own entrance located at grade with no units on top, why not consider them townhouses and use the IRC? Thus, you can avoid the more restrictive fire wall separation of the IBC to use the separation wall requirements of the IRC.