Ceiling Pocket borders entire room.

[eefire]

Good day!

I need some help. I'm finishing up the final design of a new BMW Dealership in Las Vegas and the main show room area has and enclosed room (28'X120').
The room has a "reverse soffit" border against all walls. The lower ceiling is at 15'-0'. The high ceiling elevation in the bordering pocket is 18'-0". The width of the pocket on the 28'-0" walls is 3'-0". The pocket along the longer walls is 2'-6". NFPA #13 2013 edition addresses ceiling pockets and skylights, but not surrounding pockets as described above. It doesn't see logical that these pockets should be protected. The entire floor area is protected used 11.2k Tyco E.C. at 16X16 spacing.

Anyone out there have a similar situation or information for me?

Thanks!
Jeremy in Vegas.

 

[fpst]

If I understand you right, you're saying on the border of the room, the ceiling is higher. There is a solid barrier extending down from this higher ceiling to the lower ceiling in the center of the room, otherwise it would be a floating cloud ceiling.

If that is the case, then it should look like this, except at the edges:

If that is true, then I would definitely consider that a ceiling pocket, a fire could start beneath it and heat could accumulate in the very large pocket (if it's continuous all the way around the room), preventing the lower sprinklers from activating in time. If that is the case, then I'd put sprinklers there per 13.

 

[TravisMack]

While I agree that it seems odd to have to put sprinklers in there, I think you will have to do so per the standard. The volume of your pocket exceeds 1000 cubic foot. That I think is your killer - the pocket volume.

My first thought was to put 4.2k sprinklers in there to cut down on the discharge. But, being a showroom, you are basically a parking garage and that is OH1. Small orifice sprinklers are not allowed in OH1.

I am assuming these will be on the end of a line. Just put the 5.6k in a minimum pressure and keep the pipe size large enough to those that you don't burn more than 0.2 psi total if possible. Then, you won't over-discharge your Ex Cov sprinklers at the main ceiling.



Travis Mack
MFP Design, LLC

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[LayoutLabor]

This is close to a similar situation we had in Tampa, there was a 12" deep pocket that surrounded the entry corridor into the basketball courts. With proving to the AHJ the entirety of the pocket was less than 1000CuFt in volume is became a non-issue even those the pocket was over 350' long X 50' feet across, 12" wide and 12" deep.

If you could convince the GC/Arch to put (2), 8" wide bulk head x 36" deep, in the center of the pockets, spaced at least 10' apart you could provide the coverage with (2) sprinklers between the bulk heads. These bulkheads would separate the pockets by the minimum of 10', with a protected pocket. If you can't get the GC/Arch to sign on with a way to split the pocket up you are more than likely stuck with protecting the entire pocket as it is over 1000CuFt in volume.

Hopefully this will generate some ideas on separation of pockets, so the entire pocket does not need to be protected. Just make sure that pocket does get over 3ft deep.

 

[eefire]

Thanks for the pointers. I have an RFI into the architect to raise the center ceiling to within 12" of the higher ceiling in the reverse soffit. Fingers are crossed.