Sprinklers for Continuous 3'-10" Cloud Ceilings?

10/28/2024

When is a cloud ceiling a ceiling, and when is it an obstruction?

I have a project with a 2-story lobby that has a mezzanine waiting area and clouded ceilings. The clouds are 3'-10" wide continuous clouds that run east/west across the room.

The rows of clouds are spaced 4'-0" apart from each other but will have lights and diffusers between them serving the space. Spacing between the clouds and the wall varies but narrowest dimension is 2'-0".

Even better, the roof above the cloud ceiling is sloped greater than 2/12" and will require an increased design area and sprinklers at the peak. The architect's intent was to not require sprinkler coverage below the ceiling clouds and consider them an obstruction not wider than 4'-0".

I am not as comfortable with this but wanted to bring it up for discussion. I did see a forum post about this come up in 2022 but was wondering if anyone had additional comments. Thank you!

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5 Comments

Pete H

10/28/2024 08:04:23 am

Do you happen to know the difference in elevation between the deflectors at the top and the 3'-10" wide ceiling clouds? Also what type of heads are being used?

Glenn Berger

10/28/2024 08:36:07 am

What is the difference in elevation between the cloud ceiling / obstruction and the ceiling deck above?

It does sound like that the ceiling plus the lights and diffusers form a complete obstruction, which will require sprinklers in the "cloud ceiling."

Dan Wilder

10/28/2024 08:41:36 am

Yes....and no...

NFPA's preface is (paraphrased) " Sprinkler everything" then provides a lot of paths to remove sprinklers.

In your case, sprinklers are at the sloped roof deck to start (13-22-9.1.1(1))
The description of lower elements does not comply with 13-22-9.2.1.1 for non-combustible concealed space.
Added horizontal obstructions that are not over 48" in the least dimension = no additional protection beneath (13-22-9.5.5.3.1)
This also assumes that the lights and diffusers are not attached to the ceiling strips creating locations that are greater than 48" in the least dimension.
**Did not state/ask what elevation is are the ceilings and lights so assumption is >18" (13-22-9.5.5.2.1)
Does not comply with a cloud ceiling so no omission of sprinklers at the roof deck, including that no ceiling is >48", gaps are too large (13-22-9.2.7)

So, per 13 as it reads, no protection beneath.

But...

Now the more practical side is going to say that if you are standing on the ground and between the lights, diffusers, duct, ceiling strips, and whatever else may be visible, if you cannot see the sprinklers/roof deck (entirely or in large areas), additional sprinklers should be used to provide floor coverage.

Chris Nelson

10/28/2024 09:23:45 am

Architects and their pursuit of aesthetic is the antithesis of FPEs and their pursuit of safety

Jack G

10/28/2024 09:30:10 am

Agree with above. The clouds should have sprinklers in them or dropped thru the open spaces and armed to 6 inches beneath them in a spacing pattern to cover the floor.

Sprinklers for Continuous 3'-10" Cloud Ceilings?

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