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Penetration of supporting construction

R

Robert

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Jan 29, 2016
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Pinole, CA
I am proposing a through penetration of supporting construction (2 hr) in an exterior wall. If the wall is not rated based on fire separation distance from property line, does the 2 hour rating need to be maintained on the exterior side (in addition to the interior)?
 
I'm not sure exactly of what you're trying to describe. What type of "supporting construction": beam, joists, bracing, etc.?
 
IIIB construction?...No requirement to rate penetrations for assemblies that are not required or constructed by Ch. 7...(AKA Ch. 6 is what yours sounds like)....This is a terribly quick explanation and technically Ch. 4 probably has some stuff that may send you to 7, but anyway....
 
Thanks. It's VB construction, and I'm penetrating an exterior wall with 2" pipe. The floor/clg. needs to be a 2 hour assembly (B/R3 separation, unsprinklered), and I need the supporting construction to be the same 2 hour rating per the plan checker. Plan checker wants a firestop detail, so I'm not sure if I need to add gyp. sheathing and pipe perimeter compound on the exterior (in addition to the interior) to satisfy the 2 hour supporting construction request. The exterior wall is 20' from the property line.
 
If the assembly being penetrated is not required to be rated, then there is no need for a firestop system. If the pipe is structural and requires a 2-hour rating, then it needs to be protected for the full length, whether its interior or exterior.
 
Is this podium construction (i.e. type V-B over type I/II)?

If so, I believe what you are asking is "Does a penetration through the wall of the lower podium (Type I/II const.) require protection of the penetration?" To answer that, we need to know more about the podium construction, specifically what type (betting on I-B given the 2-hr requirement).

If Type I-B, Table 601 requires walls to be 2-hr construction. This is a requirement for rating from both sides (typical); therefore, your penetration will be a through penetration that is typically addressed via fire-caulking and densely packed mineral wool.
 
Ty J. said:
Is this podium construction (i.e. type V-B over type I/II)?

If so, I believe what you are asking is "Does a penetration through the wall of the lower podium (Type I/II const.) require protection of the penetration?" To answer that, we need to know more about the podium construction, specifically what type (betting on I-B given the 2-hr requirement).

If Type I-B, Table 601 requires walls to be 2-hr construction. This is a requirement for rating from both sides (typical); therefore, your penetration will be a through penetration that is typically addressed via fire-caulking and densely packed mineral wool.
Click to expand...
Wait, got it now...

Your looking at the requirements per IBC Table 508.4 and Section 711.2.3 (below).

Construction supporting the horizontal separation between the B and R-3 occupancy requires protection from both interior and exterior. But note that this is only for the supporting elements. If you are not penetrating a structural wall, no rating is required (ex. no rated wall if column and beams are wrapped/treated). The through penetration will be typically addressed via fire-caulking and densely packed mineral wool. As an example, you could use Hilti W-L-1058 (linked).


711.2.3 Supporting Construction
The supporting construction shall be protected to afford the required fire-resistance rating of the horizontal assembly supported.
Exception: In buildings of Type IIB, IIIB or VB construction, the construction supporting the horizontal assembly is not required to be fire-resistance-rated at the following:
1. Horizontal assemblies at the separations of incidental uses as specified by Table 509 provided the required fire-resistance rating does not exceed 1 hour.
2. Horizontal assemblies at the separations of dwelling units and sleeping units as required by Section 420.3.
3. Horizontal assemblies at smoke barriers constructed in accordance with Section 709.​
 
What Ty J. posted makes a good point. You do not need a 2-hour horizontal separation if the building will comply for height and area per the nonseparated occupancies method. If it can be nonseparated occupancies (the most restrictive occupancy will dictate height and area), then the only separation you need is the dwelling unit separation, and per Section 711.2.3, Exception 2, that Ty J. posted above, Type VB construction does not need to have an equal rating for the supporting construction for the horizontal assembly.
 
Thanks.....I need the 2 hour horizontal separation....it is a separated mixed use building, R-3 over B. I understand the exception #2 you noted, and I proposed that, but my client (and plan checker) is wanting the supporting construction to be rated (even though the exception allows no rating with dwelling above). So My question is: do BOTH sides of the exterior supporting wall need the 2 hour rating (as opposed to just the inside). If I need to add gyp sheathing on the exterior of the wall to achieve the 2 hour rating, it will be out of plane with the residential story above (this is an existing building). I hope this is making sense.
 
You don't necessarily need separated occupancies. Just because you have mixed uses does not mean they have to be separated. What are the floor areas of the stories?
 
If the client is requiring it, even though the code may not, then I guess there's not much you can do. If the wall is supporting the horizontal assembly, then you need protection from an interior exposure only since the fire separation distance is greater than 10 feet. Area of openings and penetrations would be limited per Table 705.8.
 
The supporting construction is not a "separation" and shouldn't need a penetration to be rated as it is not preventing fire spread, just the construction staying up........
 
Thank you....that's what I wanted to know...protection from the interior only since exterior fire separation distance is greater then 10'. RLGA: the story count is 3 so I cannot use the non-separated occupancy path that I think you are referring to. Steveray: so no firestop detail required for a 2" pipe going into the supporting construction? That is one less detail I need to draw...thank you.
 
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