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Michael Chusid, RA FCSI CCS
Senior Member
Username: michael_chusid

Post Number: 296
Registered: 10-2003


Posted on Wednesday, July 05, 2017 - 03:01 pm:   Edit PostDelete PostPrint Post

1. What term means the space above a suspended ceiling and below the structural deck above the ceiling?
-- If it is used for air distribution, it is a "plenum".
-- Is "ceiling cavity" clear enough? "Above-ceiling cavity" "Cavity between suspended ceiling and structural deck above ceiling"?
-- Does "attic" work if the structure above is a roof? If so, what is the word if the structure above is a floor or mezzanine?

2. What is the best term to describe what one sees overhead when the structure, pipes, ducts, and other services are not concealed above a suspended ceiling?
Michael Chusid, RA FCSI CCS
www.chusid.com www.buildingproduct.guru 818-219-4937
user (Unregistered Guest)
Unregistered guest
Posted on Wednesday, July 05, 2017 - 03:26 pm:   Edit PostDelete PostPrint Post

1. interstitial space
2. exposed structure
Jeffrey Wilson CSI CCS SCIP
Senior Member
Username: wilsonconsulting

Post Number: 218
Registered: 03-2006


Posted on Wednesday, July 05, 2017 - 04:04 pm:   Edit PostDelete PostPrint Post

I can't think of a situation where "ceiling cavity" wouldn't be clear. If a more detailed description is necessary "cavity between ceiling and structural deck" would seem sufficient.

An attic (at least by ICC definition) is unoccupied space between ceiling framing and roof rafters, which to me means attic would not be an accurate term for the space between a suspended ceiling and roof deck.

The 2nd question may vary for different situations. I typically refer to "overhead structure" and "exposed underside of deck" when specifying painting applications; and usually distinguish between pipes, ducts, and other services in occupied spaces and those in mechanical spaces to indicate field painting requirements.
Jeffrey Wilson CCS CSI SCIP
Wilson Consulting Inc
Ardmore PA
Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP
Senior Member
Username: specman

Post Number: 1463
Registered: 03-2003


Posted on Wednesday, July 05, 2017 - 05:06 pm:   Edit PostDelete PostPrint Post

I concur with Jeffrey--"ceiling cavity" appears to be sufficiently descriptive of the condition.
Ron Geren, FCSI, AIA, CCS, CCCA, SCIP
www.specsandcodes.com
Brian Payne, AIA
Senior Member
Username: brian_payne

Post Number: 92
Registered: 01-2014


Posted on Wednesday, July 05, 2017 - 05:18 pm:   Edit PostDelete PostPrint Post

1. I use "interstitial space" when discussing it in the office, but I don't think I have ever used that term with a client or on drawings.

2. "Exposed Structure" or "Open to Structure" I like open to structure because it seams a bit more flexible when you also have spray fireproofing. Technically wouldn't be exposed, but that's admittedly splitting hairs.

PS. Seems like Wikipedia likes interstitial space.

https://en.wikipedia.org/wiki/Interstitial_space_(architecture)
Paul Sweet (Unregistered Guest)
Unregistered guest
Posted on Friday, July 07, 2017 - 12:31 pm:   Edit PostDelete PostPrint Post

I've always thought of interstitial space as an intermediate floor for mechanical & electrical equipment, most often in hospitals, laboratories, or factories.
Michael Chusid, RA FCSI CCS
Senior Member
Username: michael_chusid

Post Number: 553
Registered: 10-2003


Posted on Tuesday, September 01, 2020 - 10:27 pm:   Edit PostDelete PostPrint Post

The 2019 version of ASTM E1264 - Classification of Acoustic Ceiling Products, adds definition:

"plenum - space between the top (backside) of the finished ceiling and the underside of the floor deck or roof deck above."

They leave other important terms undefined. For example, Types VIII and IX ceilings are "scrubbable," but that term is not defined.
Michael Chusid, RA FCSI CCS 1-818-219-4937
www.chusid.com www.buildingproduct.guru
Dan Helphrey
Senior Member
Username: dbhelphrey

Post Number: 61
Registered: 12-2018
Posted on Wednesday, September 02, 2020 - 03:06 pm:   Edit PostDelete PostPrint Post

Harris's Dictionary of Architecture and Construction defines "plenum" as the space above a suspended ceiling, whether or not used as part of the HVAC system. (Technically, if part of the HVAC system, it is a "plenum chamber.")

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