Mechanical Duct Work "shaft" in Two Story Building

[jrtecharch]

I'm hoping to confirm my understanding that a vertical opening in a non-rated floor assembly that is only connecting two stories does not need to be a rated shaft assembly. The building is IIIB, Two stories, and sprinklered. Although per NCBC 717.6.3, I don't think it being sprinklered makes a difference. As long as we comply with #2 the walls around the mechanical shaft do not need to be rated. We comply with 712.1.9 but i don't know that this section applies because it says it pertains to applications not listed in the section, and mechanical ducts is listed in the section.

 

[steveray]

What is the use and occupancy of the building and are there combustibles in the shaft and are there sprinklers in the shaft?

 

[Yankee Chronicler]

You say your design complies with 717.6.3 #2, but your sketch doesn't show filling the annular space with non-combustible material. How will the non-combustible material be positively retained in place?

Also, you say you comply with 712.1.9, but IMHO by concealing the duct in a shaft (rated or not), you then don't comply with #3.

 

[Tim Mailloux]

You say your design complies with 717.6.3 #2, but your sketch doesn't show filling the annular space with non-combustible material. How will the non-combustible material be positively retained in place?

Also, you say you comply with 712.1.9, but IMHO by concealing the duct in a shaft (rated or not), you then don't comply with #3.

seriously? that's what details are for, this is a conceptual sketch.

 

[steveray]

And a shaft isn't required, but your drawing shows one, so that is not helping things...Maybe you need to look in IBC 712 better?

 

[jrtecharch]

You say your design complies with 717.6.3 #2, but your sketch doesn't show filling the annular space with non-combustible material. How will the non-combustible material be positively retained in place?

Also, you say you comply with 712.1.9, but IMHO by concealing the duct in a shaft (rated or not), you then don't comply with #3.

LOL, i was about to scribble in the annular space to indicate that, but was going for high level. I believe 712.1.6 would take me immediately to 717.6.3, instead of continuing to 712.1.9. And if we can retain non-combustible material within the annular space, wouldn't this then be in compliance?

 

[jrtecharch]

What is the use and occupancy of the building and are there combustibles in the shaft and are there sprinklers in the shaft?

Building is not sprinklered, but there will not be anything combustible behind the wall. it is purely for the ductwork. Occupancy is non-separated business and assembly.

 

[jrtecharch]

And a shaft isn't required, but your drawing shows one, so that is not helping things...Maybe you need to look in IBC 712 better?

We are concealing the ductwork behind a wall, yes, but isn't the definition of a shaft connecting vertical openings in successive floors? There is only an opening in one floor.

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[mtlogcabin]

but isn't the definition of a shaft connecting vertical openings in successive floors? There is only an opening in one floor.

Yes that is the definition
A shaft enclosure is constructed as a fire barrier
You can have a Shaft Enclosure constructed inside of shaft

713.2​

Shaft enclosures shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies in accordance with Section 711, or both.

[BF]SHAFT. An enclosed space extending through one or more stories of a building, connecting vertical openings in successive floors, or floors and roof.
[BF]SHAFT ENCLOSURE. The walls or construction forming the boundaries of a shaft.

 

[ICE]

How much more would a rated shaft add to the cost as opposed to a generic shaft?

 

[Yankee Chronicler]

seriously? that's what details are for, this is a conceptual sketch.

Really? I wouldn't have guessed.

Sure, it's a conceptual sketch -- one that doesn't show a conceptually compliant design. If it was the design intent to provide firestopping in the annular space, the sketch should have in some way indicated that. Otherwise, we can only conclude that it wasn't intended.