spinklers above a wood slat ceiling

[jsiedler]

Hello, I have a question relating to fire sprinkler systems above a wood slat ceiling where the space above is a open plenum return. The space is about 5,500 SF and in a type 5, 1-hour rated construction type. The wood trusses have two layers of gyp board on the bottom chord of the truss but that is the only combustible material in the plenum space. Not all of the walls go to deck so conceivably hot air can move around in this open area above the ceiling. In my mind if we have locations where there are wood slat ceilings (Armstrong, class A rated) we have upturned and downturned heads then there should be coverage. The whole plenum space does not need to have sprinklers in it to meet code. The fire department is saying that if there is an open plenum, and not all of the walls go to deck, then if there is a fire that starts in this space heat will dissipate and won't activate the upturned heads above the wood slat ceilings. I am not seeing anywhere in the code that states this is a requirement. Again there are two layers of gyp board on the bottom chords of the wood trusses and there is no wood in the plenum and the walls are made with metal studs. The only wood in the ceiling is where the wood slats are. He is talking about putting a gyp board lid above the wood slat ceilings to contain the heat so that the upturned heads activate. Any help in understanding the sprinkler requirements above a wood slat ceiling with an open air plenum (possibly non-combustible) would be appreciated.

Thanks,

Jim

 

[TravisMack]

A picture of this would be worth a thousand words to make sure we get what you are asking.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[jsiedler]

 

[TravisMack]

My take from what I see is the very basics. Start with all areas are to be protected.

Now, I would believe that your plenum space is non-combustible from your description.

For the slatted area, you put sprinklers at the gyp ceiling (bottom of trusses). Then, if the wood slat ceiling is such that it creates an obstruction, then put sprinklers below that ceiling as well. I can't see why a gyp lid would matter. The slats may or may not be far enough apart so that they don't even constitute an obstruction and sprinklers at the hard ceiling are adequate.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[cdafd]

Jim

Are you the building designer and not fire sprinkler company??

 

[cdafd]

Should have asked how do you define wood slat?

Is there any opeing between the slats??


Something Like this where there are no openings:::

http://www.screenwood.com.au/images/pageheroes/applications/external/08.jpg

Or this::

http://www.martinintegrated.com/img/wood/UCI-Business10.jpg

 

[jsiedler]

I am the building designer. I am trying not to have to put a hard lid above the wood slat ceiling. We are using an Armstrong product, class A rated, with 6" wood slats and a 1/2" gap between the slats (and black felt at the gaps so you can't see through them but the felt is porous, obviously). This product would be the only material that is exposed to the plenum and is combustible. I think that we are covered with just sprinkler heads. My reasoning is that we will have upturned and downturned heads at the wood slat ceiling for coverage in the event of a fire. The fire department is saying that since there are gaps between the wood slats heat will not collect at the wood ceiling and will go through the gaps. Once the heat goes through the gaps it will dissipate in the open return plenum and not trigger the upturned heads. I don't see anywhere in NFPA 13, IBC, etc that says you need to have a gyp lid above a wood slat ceiling to contain the heat so the the sprinklers are triggered.

Another line of reasoning that I've heard is that if you have a gyp board lid above a wood slat ceiling then it is no longer exposed to the open plenum and no upturned heads are required. This seems like fuzzy logic to me that I don't understand and again I can find no reference in the code that allows this exception.

 

[TravisMack]

Just ask the fire official for a code/standard section to back up his response. If he doesn't find one, then follow NFPA 13 direction.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[cdafd]

Agree needed above and below

So you are meeting NFPA 13

Now if they have a fire protection engineer on the ahj staff, that says otherwise?? Well would ask for some documentation.

Do you have a fire sprinkler company advising you.

If so have them show you the open grid ceiling exception, which you do not meet. But may help with your argument

 

[cdafd]

Which edtion of NFPA 13 is the ahj using??

 

[jsiedler]

they are using 2013.

 

[cdafd]

There is a couple of things in the 2016 that might help. More than likely Monday before I can post them...


*****. Do you have a fire sprinkler company advising you????

 

[cdafd]

NFPA 13 2016

Might with a strech meet cloud ceiling:

3.3.5.1 Cloud Ceiling. Any ceiling system installed in the same plane with horizontal openings to the structure above on all sides. This does not include sloped ceilings as defined in 3.3.5.4.

If so look at 8.15.24:

8.15.24 Cloud Ceilings.

8.15.24.1* Sprinklers shall be permitted to be omitted above cloud ceilings where both of the following apply:


(1)*
The openings around the cloud and the maximum sprinkler protection area meet the requirements of 8.15.1.2.1.2 and Table 8.15.24.1


(2)
The requirements of 8.15.24.2 are met.


Table 8.15.24.1 ::::: table does not copy



Maximum Sprinkler Protection Area Based on Ceiling Cloud Width and Opening Width


8.15.24.2 When sprinklers are omitted from above a cloud ceiling in accordance with 8.15.24.1, the requirements of this section shall apply.


8.15.24.2.1 All sprinklers shall be quick response standard spray or extended coverage pendent or upright sprinklers.





Plus look at:

8.15.1.2.1.1 The space shall be considered a concealed space even with small openings such as those used as return air for a plenum.



8.15.1.2.1.2 Small openings with a combined total area of not more than 20 percent of the ceiling, construction feature, or plane used to determine the boundaries of the concealed space shall be permitted where length greater than 4 ft (1.2 m) shall not have a width greater than 8 in. (200 mm).



8.15.1.2.1.3 The space above cloud ceilings meeting the requirements in 8.15.24.1 and having openings with a combined total area of not more than 20 percent of the ceiling, construction feature, or plane used to determine the boundaries of the concealed space shall be permitted.