Sprinkler Above Ceiling with 2'x4' Openings?

8/22/2022

I have a strange situation: a concrete deck with surface-mounted light fixtures.

We then have a ceiling grid that is suspended about a foot below that, where they have 2-ft x 4-ft plastic grid fixtures below the lights to allow light to shine through.

The openings are in the middle of the room so it's not a "cloud ceiling", and they represent more than 20% of total ceiling space.

Do I simply provide coverage below grid as normal and above the ceiling grid 24-ft in every direction above the openings in accordance with NFPA 13 2016 8.15.23.3.1?

Thanks in advance.

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8 Comments

Pete H

8/22/2022 07:29:29 am

Sounds like it. I'd say yes.

Glenn Berger

8/22/2022 08:18:13 am

The more than 20% of ceiling space is the kicker. Need more information of the occupancy and construction of the space to advise.

Matt Laughlin

8/22/2022 04:49:31 pm

Office space, light hazard w/ brick walls and concrete deck where the lights in question are. A few ord haz storage spaces but no grid in those.

Dan Wilder

8/22/2022 08:22:54 am

I guess it's a Monday and I'm not picturing this correctly.

Below each light fixture is the grid fixture that is "open", with the remaining tiles being solid, and the cumulative open % pushes you out of it being a cloud ceiling?

Can you just ask the GC to bring that ceiling up a 1/2" and just protect below (assuming floor coverage is not an issue)? You could argue the ceiling being 12" down is OK, but since the deflector extends a little lower, better to be safe.

If not, then your alternate approach looks correct.

Matt Laughlin

8/22/2022 04:52:06 pm

Not a bad idea. It's existing construction but the grid's at least partially coming down so we can install. I'll look into that, thx.

Todd E Wyatt

8/22/2022 08:34:24 am

2022 NFPA 13 defines a "cloud ceiling" as ...

3.3.34 Cloud Ceiling.
Any ceiling system, not including sloped ceilings, installed in the same plane with horizontal openings to the structure above on two or more sides. (AUT-SSI)

... and the following outlines when sprinklers shall be omitted in a "cloud ceiling" :

9.2.7.1*
Sprinklers shall be permitted to be omitted above cloud ceilings where all of the following apply:
(1)* The combined total area of the openings around the cloud are less than or equal to 20 percent of the area of the ceiling, construction feature, or plane used to determine the boundaries of the compartment.
(2) The width of the gap and the maximum sprinkler protection area are in accordance with Table 9.2.7.1.
(3) The requirements of 9.2.7.2 are met.
(4) Spaces above cloud ceilings contain either noncombustible or limited-combustible construction with minimal combustible loading.

Review Table 9.2.7.1 Maximum Sprinkler Protection Area Based on Ceiling Cloud Width and Opening Width.

Lastly, review 9.2.7.2 which is referenced in 9.2.7.1 (3) :

9.2.7.2
When sprinklers are omitted from above a cloud ceiling in accordance with 9.2.7.1, the requirements of this section shall apply.
9.2.7.2.1
All sprinklers shall be quick response standard spray or extended coverage pendent or upright sprinklers.
9.2.7.2.2
Maximum cloud ceiling height shall not exceed 20 ft (6.1 m).

Matt Laughlin

8/22/2022 04:54:59 pm

I don't think cloud applies because the ceiling grid isn't open on at least two sides; it's tight to wall on all four. I think I have to treat the grid as one big obstruction.

Jesse

8/22/2022 09:29:32 am

Admittedly I'm having trouble picturing this. I think, by what you're describing, you'll need to protect above and below.

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Sprinkler Above Ceiling with 2'x4' Openings?

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