Re: Mechanical Shaft

[Glennman CBO]

2006 IBC, IMC.

Condition: A mechanical shaft from roof top unit on 2 story building serving the 1st floor (both floors). Type V-B construction. Sprinklered due to area increase.

Section 707.2 exception #7. A shaft enclosure is not required for a floor opening or an air transfer opening that "complies with the following":

7.1. Does not connect more than two stories.

7.3. Is not concealed within the building construction.

I've always taken the statement "complies with the following" as referring to all the "following" conditions, not just one or two of them. The designer is saying that the shaft does not require rating due to the fact that it does not connect more than two stories, but I'm saying that it needs to be rated due to being concealed within the building construction.

Am I reading this section right?

 

[north star]

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Yes! Must comply with both / all of the provisions.



Ask the designer to provide you with a code section that they CAN install it

that will allow it to be installed without the rating. Place the tasking of

compliance on them!



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[TimNY]

agreed. i would interpret it as "complies with all of the following"

 

[88twin]

i would say it doesn't matter.

If it runs from the roof to the first floor it connects more than two stories.

707.2 #7 refers to openings between no more than two stories, example: a stairway connecting two floors of a four story bldg that is NOT part of the required moe.

and yes to answer your question it's All of the conditions. The conditions make sense if one applies them to a stairway.

 

[Glennman CBO]

I'm ok, your ok. I thought I was reading this right. I've already contacted the designer and he is working on it.

88twin...are you saying that if the attic is included, that it, in a sense, is connecting "more than two stories" due to the attic?

That's an interesting take on it. I'll have to think about that.

 

[globe trekker]

.

See the definition of "story" in the `06 IBC:

STORY:

That portion of a building included between the upper surface of a floor and the upper surface of the

floor or roof next above (also see "Mezzanine" and Section 502.1). It is measured as the vertical

distance from top to top of two successive tiers of beams or finished floor surfaces and, for the topmost

story, from the top of the floor finish to the top of the ceiling joists or, where there is not a ceiling, to

the top of the roof rafters.

.

 

[mtlogcabin]

floor opening or an air transfer opening

A shaft and an air transfer opening are not the same thing.

Since this is a duct and not an air transfer opening I believe your answer is in

712.4.2 Nonfire-resistance-rated assemblies.

Penetrations of horizontal assemblies without a required fire-resistance rating shall meet the requirements of Section 707 or shall comply with Section 712.4.2.1 or 712.4.2.2.

712.4.2.1 Noncombustible penetrating items.

Noncombustible penetrating items that connect not more than three stories are permitted, provided that the annular space is filled with an approved noncombustible material to resist the free passage of flame and the products of combustion.

712.4.2.2 Penetrating items.

Penetrating items that connect not more than two stories are permitted, provided that the annular space is filled with an approved material to resist the free passage of flame and the products of combustion.

 

[88twin]

thanks mtlog, i believe you got the right section for us.

712.4.2.1 noncombustible penetrating items- not more than three stories

712.4.2.2 penetrating items- not more than two stories, refers to penetration of a SINGLE nonfire-resistance-rated FLOOR (not more than two "stories")

 

[Glennman CBO]

Would a shaft that is made up of wood 2x4's and is penetrating the non fire rated floor be considered a non combustible penetrating item?

I believe that a non combustible duct can penetrate the floor, but if it is enclosed inside a shaft made of wood, then it's the wood that is penetrating.

 

[AegisFPE]

712.4 is referenced in Exceptions 3 and 4 of 707. Therefore, treatment of the penetration of a horizontal assembly could be in lieu of shaft construction, as referenced in 712.4 (amost a circular reference here).

If there is already a shaft, you should look at where the penetrant enters the shaft, as opposed to where the shaft passes through the floor.

 

[88twin]

man oh man, opened a can of worms here in the office.

official interp here is that "more than two stories " does not include unoccupied attics and basements

sooo penetrations through those spaces in addition to two stories is OK

same would hold true for three stories

if the space is not counted as a "story" then....

my contention is that to connect two stories requires a floor ceiling penetration of some type. so if im allowed to connect two stories that equates to one floor /ceiling penetration, three stories = two floor/ceiling penetrations and so on. i don't care what one calls the space on the other side of the penetration it is still "more than" two stories or three as the case may be. i was told "no two stories and a basement is ok or two stories and an attic"

to "just count the stories as defined in the code"

 

[mtlogcabin]

"just count the stories as defined in the code"

A basement is a story. It does not contribute to the area or height but it does count when connecting "stories" with openenings

STORY. That portion of a building included between the upper surface of a floor and the upper surface of the floor or roof next above (also see “Mezzanine” and Section 502.1). It is measured as the vertical distance from top to top of two successive tiers of beams or finished floor surfaces and, for the topmost story, from the top of the floor finish to the top of the ceiling joists or, where there is not a ceiling, to the top of the roof rafters.

STORY ABOVE GRADE PLANE. Any story having its finished floor surface entirely above grade plane, except that a basement shall be considered as a story above grade plane where the finished surface of the floor above the basement is:

BASEMENT. See Section 502.1 and 1612.2.

BASEMENT. That portion of a building that is partly or completely below grade plane (see “Story above grade plane” in Section 202). A basement shall be considered as a story above grade plane where the finished surface of the floor above the basement is:

1. More than 6 feet (1829 mm) above grade plane; or

2. More than 12 feet (3658 mm) above the finished ground level at any point.

707.4 Fire-resistance rating.

Shaft enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more, and not less than 1 hour where connecting less than four stories. The number of stories connected by the shaft enclosure shall include any basements but not any mezzanines. Shaft enclosures shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.

If the shaft enclosure would apply to a connected basement then the exceptions for the number of stories would include connections/openings into basements.

 

[Glennman CBO]

I can see 712.4.2.1 applying in this case even if the duct is enclosed in a shaft IF they seal the duct penetration at the floor line. That way the shaft (area surrounding the duct between the duct and the shaft wall) will not actually be communicating between the floors.

The main issue here is that the ductwork is already installed, and they have details showing drywall inside the "shaft". This is a two story building plus a basement that was built in sections in a neighboring state and delivered and stacked with a crane.

The other problem they have is where the "shaft" that doesn't have the drywall in it, is abutting a rated elevator room that is supposed to have drywall on both sides of that wall too. The duckwork will need to be removed in order to install the drywall at least in those areas. This entire project is a cluster.

Thanks for the help.

 

[peach]

kinda have to go with not all exceptions apply.. look at the glazing requirements in the IRC .. they are pretty specific about ALL when they mean ALL.

Looked at 707.. since Exception 7 specially address I-2 and I-3, then in exception 7.4 again addressed I occupancies