Fire Separation of Rooftop Exit Enclosures

[sunyaer]

This is the interpretation of Fire Separation of Rooftop Exit Enclosures: https://boabc.org/wp-content/uploads/2021/07/File-No-18-0100.pdf

"The walls of the rooftop exit stair would be exterior walls, and Sentence 3.1.7.3.(3) states "Exterior walls shall be rated for exposure to fire from inside the building". Constructing exit stair exterior walls as fire separations rated from inside the exit would provide minimal protection to the exit. Therefore, it is interpreted that exit stair exterior walls at a roof are not required to be fire separations."

It looks to me, there is a reasoning part missing before "Therefore", that is, "Constructing exit stair exterior walls as fire separations rated from inside the exit would provide minimal protection to the exit" can not derives to "exit stair exterior walls at a roof are not required to be fire separations". The only thing which I can think of makes the logic valid is "there is no fire inside the exit", so the logical reasoning looks like this: the exit stairs exterior walls are rated from inside the exit, while there is no fire inside the exit, so that the walls are rated as zero hour or not required to be fire separations.

Am I correct? Please comment with your thoughts.

 

[tmurray]

Mostly correct.

The issue discussed in this decision is that wall rating happens from both sides for walls located within the building and on the inside for exterior walls. In the case where you have an exit to a rooftop occupancy, only one side of the exit enclose would theoretically be rated (the inside). However, the question is what protection this provides? If fire has compromised an exit, it is unlikely that the space is occupied as the fire would need to breach a fire separation of at least 45 minutes. Additionally, there is nothing in the code to require a fire separation between the exit and rooftop occupancy.

The other thing to keep in mind is that the codes largely stay away from requirements related to intentional acts of damage to a property (like arson). This is due to the fact that it is at best challenging to regulate construction to meet these types of issues. I only bring this up because a fire starting in an exit enclosure is exceptionally rare, except for arson. Even then, there are typically issues related to the fire code involved (illegal storage).

 

[sunyaer]

Mostly correct.

If fire has compromised an exit, it is unlikely that the space is occupied as the fire would need to breach a fire separation of at least 45 minutes. Additionally, there is nothing in the code to require a fire separation between the exit and rooftop occupancy.

What does "the space" refer to?

The other thing to keep in mind is that the codes largely stay away from requirements related to intentional acts of damage to a property (like arson). This is due to the fact that it is at best challenging to regulate construction to meet these types of issues. I only bring this up because a fire starting in an exit enclosure is exceptionally rare, except for arson. Even then, there are typically issues related to the fire code involved (illegal storage).

For arson, police will deal with it, while for illegal storage, fire code will do its job, correct?

 

[tmurray]

The adjacent spaces that would need to access the exit.

Typically, fire code violations are policed by fire prevention officers.