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» ICC Bulletin Board » Code Chat » Building and Residential Codes -- Non-Structural Issues » Floor penetrations of rated assemblies

   
Author Topic: Floor penetrations of rated assemblies
olc
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The penetration of the floor membrane of a ceiling-floor assembly is not really addressed in the code. For example, a steel duct from above through the floor into the space between the floor and ceiling below (of a wood frame rated assembly) - fire damper?
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peach
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If it's a required fire rated assembly,they either build a shaft or install dampers.

Not really enough information to say more.

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Francis Vineyard
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Which code edition, 2006 IBC?

Then you may want to start with Section 712.4 where it will eventually take you to Section 716.

Can't say if you will need to take a look at IMC as well but without knowing more for example; what is the ceiling-floor assembly part of?

And what is the purpose of the air duct and it's origination? Its termination?

Hope this will lead you in the right direction.

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Builder bob
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I guess the question is..... Using a wood open truss floor system, the return duct from a downdraft HVAC unit is being fed thru the top of a rated floor ceiling assembly. The supply, is also going thru the top of the same assembly.

Therefore, If the floor/ceiling assembly is a rated assembly, and the duct work is penetrating the top portion of the floor/ceiling assembly, is a fire damper required?

Open wood trusses for floor system
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[IMG]

Rough diagram for discussion for fire dampers.

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[ 06-15-2009, 06:26 AM: Message edited by: Builder bob ]

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klarenbeek
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607.6 of 2006 IMC. It's not a through penetration, so 607.6.1 which requires a fire damper does not apply. It sounds like this is an engineered truss system with the duct running below the floor in the trusses such as in an apartment building. If this is the case, the only time a damper is required is if the drywall ceiling is penetrated, with a radiation damper at the ceiling line per 607.6.2. It is a rated assembly, but think of the actual point of the fire barrier as being the drywall of the ceiling. I see this a lot in apartments, with the contractor using downflow furnaces with duct running through the trusses and then back up through the floor to the register. If gypcrete on top of the wood floor is used to achieve part or all the required rating, that changes things and a fire damper would be required.

Hope this helps!

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John Drobysh
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olc -

If memory serves me correctly (and I'll know by midday if it does not! [Eek!] ) Dampers are NORMALLY required for 'through penetrations'. What you are dealing with here is a 'membrane penetration'. They do get treated differently.

In my NYS Code 711 discusses penetrations (through AND membrane). At a glance, it may only require firestopping, but give it a good read and be sure.

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Examiner
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Section 712.4.1.2 addresses membrane penetrations of horizontal assemblies as well. The membrane is the ceiling of the rated system. A through penetration (Section 712.4.1.1.2)is through both the membrane and floor.
Section 712.4.1.3 addresses penetrations of horizontal assemblies with ducts and air transfer openings must comply with 716.

Get the Commentary it has graphic examples.

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Builder bob
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Ceiling dampers
Ceiling dampers are used to limit the passage of heat in fire resistive floor-ceiling or roof-ceiling assemblies where ducts or other penetrations are made only through the ceiling membrane of the fire resistive assembly. Fire resistive ceiling membranes are part of floor-ceiling or roof-ceiling assemblies that have been evaluated for their fire resistive capabilities when evaluated in accordance with the Standard for Building Construction Materials, ANSI/UL 263 (ASTM E119, NFPA 252, UBC 7-1). Fire rated designs evaluated by UL are published in UL's Fire Resistance Directory.

Since ceiling dampers are intended to function only as heat barriers, and the building codes have not defined the use of these products in so far as their use as smoke barriers, the UL certification does not include the use of these products to limit the migration of smoke.

Special notice regarding ceiling dampers: This is to advise that UL has not authorized the use of ceiling dampers in Design Number L528 as published in UL's fire resistance directory. This information is being provided in response to publications by other certification agencies that state that ceiling radiation dampers and insulated plenum boxes are acceptable for installation in partition types L-528.

For additional information regarding dampers, see the UL Marking Guide for Dampers for Fire Barrier and Smoke Applications and Ceiling Dampers. The guide was developed for use by contractors, code and inspection authorities, installers, users and system designers to aid in the understanding of the scope of UL certification of dampers. The guide is also intended to assist in determining the suitability of these products for use in specific applications


HORIZONTAL DAMPERS
One of the most common questions concerning dampers is the use of horizontal dampers.
The correct damper depends on the situation. Fire Resistive Assemblies come in many types.
Essential to all assemblies is the use of a protection material for the structural element
supporting the floor. The entire assembly must also resist the passage of heat through to the
top of the floor. The membrane ceiling, acoustical material and ceiling grid or gypsum
3
Damper Marking & Application Guide April 2003
wallboard never comprise the hourly rating by itself. The membrane retards the passage of
heat into the plenum space. Duct openings through the membrane only, or through the
entire fire resistive assembly, are treated differently.
The Standard for Air-Conditioning Systems, NFPA 90A provides guidance for ducts
penetrating through fire resistive assemblies. As a rule, vertical ducts rising through fire
rated floors are to be protected within fire rated shaft enclosures. There are only a few
exceptions to these criteria in NFPA 90A. As the fire resistive shaft rises through the
structure, it is not necessary to protect the opening at the floors the duct passes through
because the duct is located in a fire rated shaft. The shaft should be penetrated
horizontally so that vertical dampers can be used to protect the penetration through the
shaft.
If the situation arises that a vertical duct extends up through a fire rated floor assembly by
one of the exceptions in NFPA 90A, then the horizontal type fire damper is the appropriate
damper to use.

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John Drobysh
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Examiner -

Not to hijack, but the NYS BC defines 'membrane' to include the floor, not just the ceiling. Is the ICC BC different? Just curious...

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Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming, "Wow, what a ride!!!"

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klarenbeek
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Sorry. Hope I didn't confuse anyone by mentioning radiation dampers. They are to be used when penetrating only the drywall membrane of the assembly, as when there is an upflow furnace with the duct running overhead in the trusses and then turning back down, without penetrating the floor above. Going all the way thru both floor and ceiling would require either a shaft or fire damper. If it is open trusses, I don't know of any fire dampers listed for that type of assembly (I could be wrong though, don't see that application much)
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peach
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until the OP gives us more information, we're all just speculating..

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olc
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To clarify my question a little: IThe specific case is a open web wood joist floor ceiling system (it is a multi family). Supply and return branch ducts go down through the floor, travel horizontal a bit and terminate at ceiling grille/diffuser which has a ceiling radiation damper. The question is about the penetration of the floor membrane of the assembly.
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Builder bob
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Townhome (dwelling unit muti-story) or the dwelling unit stacked on top of each other?

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Can you build to minimum standards? FWIW - MCP, CBO, CPE, CI, CFPE, ASCET
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TJacobs
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olc: we could use a section view...

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