# Rated Acoustical Ceiling



## tmurray (May 19, 2015)

I have an existing building that a developer wants to change the occupancy on. The owner is stating that the ceiling tiles are rated for 1 hour. There are no clips to keep them in place, but the T would support their use. My question is; are the ceiling tiles usually stamped with identifying marks on the back to indicate their rating. I seem to remember seeing it once.


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## JPohling (May 19, 2015)

usually there is a manufacturer # that you can look up on the back of the tile.  or stamped fireguard possibly depending on the manufacturer.  clips not necessarily required.


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## cda (May 19, 2015)

...........


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## cda (May 19, 2015)

Why the one hour though ??


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## cda (May 19, 2015)

Previous d- cussin

http://www.thebuildingcodeforum.com/forum/commercial-building-codes/16297-use-suspended-ceiling-fire-separation.html


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## tmurray (May 19, 2015)

cda said:
			
		

> Previous d- cussinhttp://www.thebuildingcodeforum.com/forum/commercial-building-codes/16297-use-suspended-ceiling-fire-separation.html


Both stories are the same occupancy, the rating is to prevent collapse of the structure.


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## tmurray (May 19, 2015)

cda said:
			
		

> Why the one hour though ??


NBCC 2010: 3.2.2.25.(2)(a): floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min,

The floor system is open web wood joists. As to why they went with a 1 hour over 45 minutes I cannot say.


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## cda (May 19, 2015)

I think I would require documentation of the entire ceiling system to evaluate it. The grid also has to be listed for one hour assembly.

Than is the system listed for the use!!!!  I am thinking no.


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## cda (May 19, 2015)

Fire sprinkler system in the building???


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## steveray (May 19, 2015)

I don't know that a rated "drop ceiling" meets the intent of "floor assembly" being noncombustible or fire rated.....


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## jdfruit (May 19, 2015)

The concept is "floor/ceiling" assembly; essentially "skin to skin" from top to bottom or vise versa. If the assembly has a "rated" suspended ceiling then all components of construction must be in accord with the listing. UL (USA) listings normally have more than one manufacturer for components otherwise the listing is "proprietary" for that individual manufacturer and system. Right now I don't know of any current listed suspended ceilings that form a fire rated component by themselves or are the main component in a fire rated floor/ceiling assembly. Older listings used to have them and the ones without clips usually had heavy tiles, most of them gypsum core based materials.

IMHO suspended grid fire rated assemblies are not desirable due to user or maintenance ignorance that effectively causes breaches in the system by not re-installing required clips or using standard ceiling tiles in lieu of the fire resistant tiles.


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## JBI (May 19, 2015)

The tiles, the grid, AND the suspending wire all must be per listing to qualify for the rating.

UL has listed floor ceiling assemblies that incorporate suspended ceilings.

Desirable or not, a listed assembly meets Code.


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## tmurray (May 20, 2015)

steveray said:
			
		

> I don't know that a rated "drop ceiling" meets the intent of "floor assembly" being noncombustible or fire rated.....


The intent of the code is to protect the combustible floor system from fire from the floor below, so in this case it does meet the intent of the code.


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## cda (May 20, 2015)

Ok so if you just need a barrier sounds like this would work.

Still would get documentation that the entire assembly is listed as an assembly.

To include documentation on the tiles,

So you can have them pull a per centage of the tiles you point out to check.


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