Roof Dog-House 2012 IBC Section 713

[nitramnaed]

For a tenant buildout for a restaurant we are constructing a roof dog-house over a rated shaft for HVAC and Exhaust ducts. The plan reviewer is requiring us to fire-rate the vertical dog-house wall where the ducts penetrate. With this we would need to provide some very large dampers on 8 duct penetrations $$$$$. He quotes code as follows:


713.12 Enclosure at top. A shaft enclosure that does not
extend to the underside of the roof sheathing, deck or slab of
the building shall be enclosed at the top with construction of
the same fire-resistance rating as the topmost floor penetrated
by the shaft, but not less than the fire-resistance rating
required for the shaft enclosure.

I think he is incorrect on this and this is not the condition we are proposing. I don't believe that anything the penetrates the roof needs to be rated. See attached image for what we sent him with a quote from the interpretation manual on roof penetrations.
Any comments on this would be much appreciated.

 

[RLGA]

He is off-base. The key phrase in your case is, "A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building..." (underline added). Your penetration not only does extend to the roof sheathing, deck or slab, it penetrates it.

The separation is required to protect interior spaces from the shaft. There is no need to protect the shaft from the exterior or vice versa. On the other hand, if the construction type requires rated construction for walls and roof, then the construction would require a rating per Table 601; however, rated penetrations would not be required unless needed due to fire separation distance.

 

[tmurray]

We had a similar discussion at a course here recently. An architect stated that a building inspector had required the same thing of him and he couldn't understand why the code required it. I told him it doesn't. As Ron stated, this is to separate what in a fire condition is basically a chimney from the rest of the building. Here, the ceiling of the shaft also must be rated unless it penetrates the roof. This is to prevent premature failure of the structure of the roof that is likely running through this area.

 

[nitramnaed]

OK. He backed off and now say's it's a penthouse and quoted section 1510.2.3 as the reason it's allowed. I don't know what this has to do with it but we can construct per the attached detail w/o dampers so owner and GC have removed "The Hit" they had out on us.
Thanks for the responses.

 

[Keystone]

He referenced a separate section to justify him/herself, really!!!!!!?

I have a problem with this, see and hear it all the time! Why can't people in general and then especially us inspectors just admit we are human and make mistakes?

 

[PJC89]

For a tenant buildout for a restaurant we are constructing a roof dog-house over a rated shaft for HVAC and Exhaust ducts. The plan reviewer is requiring us to fire-rate the vertical dog-house wall where the ducts penetrate. With this we would need to provide some very large dampers on 8 duct penetrations $$$$$. He quotes code as follows:


713.12 Enclosure at top. A shaft enclosure that does not
extend to the underside of the roof sheathing, deck or slab of
the building shall be enclosed at the top with construction of
the same fire-resistance rating as the topmost floor penetrated
by the shaft, but not less than the fire-resistance rating
required for the shaft enclosure.

I think he is incorrect on this and this is not the condition we are proposing. I don't believe that anything the penetrates the roof needs to be rated. See attached image for what we sent him with a quote from the interpretation manual on roof penetrations.
Any comments on this would be much appreciated.

View attachment 2560

He is incorrect. The section you have referenced above is for a shaft that terminates at the interior of the building and does not penetrate the roof assembly. Therefore, there essentially has to be a cap at the top of the shaft to continue to protect the the interior of the building. In the diagram you have shown, the exterior walls would function as a penthouse:

1510.2.3 Use Limitation

Penthouses shall not be used for purposes other than the shelter of mechanical or electrical equipment, tanks, or vertical shaft openings in the roof assembly.

As a penthouse, the exterior walls are determined whether or not they need a fire resistance rating based on the fire separation distance. The fire separation distance is measured to an adjacent lot line, imaginary lot line or the street/alley or public way. Assuming the lot line is greater than 30 feet from the exterior walls above the roof (i.e., penthouse enclosure) there is no need to provide a fire resistance rating. Refer to Section 1510 for additional requirements.

https://up.codes/viewer/general/int...5/roof-assemblies-and-rooftop-structures#1510