Sprinklers Required Below Mesh Green Ceiling?

1/10/2025

I am working on a sprinkler system where the corridor has a wooden ceiling, as shown below. Upright sprinklers protect the space above the ceiling.

I want to know whether the pendent sprinklers below the ceiling are also required?

Is this an open grid ceiling under NFPA 13?

The ceiling has the following characteristics: Bamboo ceiling panels with mesh void and solid wood frame with galvanized black metal rods as hangers for proper support, panels are to have a consistent panel size of 15 cm void between each panel and the wall and 30 cm void between the panels for the greenery to be hung.

Can anyone help me in this case? Thanks in advance.

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10 Comments

Pete H

1/10/2025 06:44:17 am

From NFPA 13 (2016 Ed.)

8.15.14 Open Grid Ceilings. Open Grid ceilings shall only be installed beneath ceilings where one of the following is met:
1) Open grid ceilings in which the openings are 1/4 in. or larger in the least dimension, where the thickness or depth of the material does not exceed the least dimension of the opening, and where such openings constitute 70% of the area of ceiling material. The spacing of sprinklers over open grid ceilings shall comply with the following:
a) in light hazard occupancies where sprinkler spacing (either spray or old style sprinklers) is less than 10 ft x 10 ft, a minimum clearance of at least 18 in. shall be provided between the sprinkler deflectors and the upper surface of the open grid ceiling. Where spacing is greater than 10 x 10 ft but less than 10 x 12, a clearance of at least 24 in. shall be provided, and at least 36 in. for old style sprinklers. Where spacing is greater than 10 x 12, a clearance of at least 48 in. shall be provided.
b) In ordinary hazard occupancies, open grid ceilings shall be permitted to be installed beneath spray sprinklers only. Where sprinkler spacing is less than 10 x 10, a minimum clearance of at least 24 in. shall be provided. Where spacing is greater than 10 x 10, a clearance of 36 in. shall be provided.
2) Other types of open grid ceilings shall be permitted to be installed beneath sprinklers where they are listed for such service and are installed in accordance with instructions contained in each package of ceiling material.

A.8.15.14 The installation of open grid egg crate, louver, or honeycomb ceilings beneath sprinklers restricts the sideways travel of the sprinkler discharge and can change the character of discharge.

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Okay, so I'm leaning towards this isn't an open grid.

It doesn't look a full 70% or greater open, it looks like it's thicker than the opening between the grid lines. But that is me evaluating based on a picture and not actual details or technical specs of the ceiling.

I'd protect underneath it, ideally with a line of corridor sidewall sprinklers.

Dan Wilder

1/10/2025 07:52:50 am

Even without the additional lower ceiling, there should be obstruction protection within this corridor due to the mostly solid cable trays and additional duct work. The added ceiling just allows the protection to be a little lower overall.

I would be dropping sprinklers to cover beneath the bamboo via a drop/arm-over/upright-pendent or a drop with a pendent and a water shield within 3" of the perimeter on the sides that do not have the additional hung greenery.

Glenn Berger

1/10/2025 08:15:58 am

Pete cited the code definition for open grid ceilings and like Dan stated, the photo does not support the open grid concept. I am in agreement with both respondents.

Chris

1/10/2025 08:33:46 am

Is this an interior finish in an egress corridor? I'd recommend looking into this as well.

Jimmy

1/10/2025 08:47:08 am

Bingo!
This should have never been approved,
BUT something tells me it was never permitted.

Hopefully it will be inspected and addressed by a qualified official.
Soon,

Jose R Figueroa

1/10/2025 12:30:50 pm

Sprinklers should be installed inside concealed spaces and beneath suspended combustible ceilings. According to my interpretation of NFPA 13, any area above a grid ceiling that does not meet the "open grid" criteria should be considered a concealed space. Therefore, sprinklers may need to be installed above it unless the construction materials and potential fire load in that space meet specific conditions that allow for an exception, as outlined in section 9.2.1 regarding allowable unsprinklered concealed spaces in the standard.

If I may add, this area originally resembled a hospital basement corridor. I find the new construction design intriguing. Why is there greenery on the false ceiling? Is it related to some environmental regulations? I might have misunderstood the description. What are the local code requirements? AHJ? Thank you

J.H.

1/10/2025 03:06:35 pm

Great feedback from all. A few years ago we had a project come through with proposed nylon mesh providing shade to an outdoor garden center, attached to the main, sprinklered structure. They came into Code compliance by providing sidewall sprinklers of sufficient coverage.

In addition to following up on the interior finishes, I would make the recommendation that the edges of the steps in the gray concrete corridor be marked in a contrasting color. One of our inspectors fell down some virtually invisible gray concrete steps, similar to that one, while walking an overhead visual inspection. They survived, but needed years of PT.

Jack G

1/10/2025 03:11:42 pm

Whether the ceiling is 70% open or not there is not enough room for the sprinklers above the mesh, so sprinkler protection must be added below. From the pictures I cannot see any visible existing sprinklers that were protecting the corridor.

James E Art Fire Protection Engineer (FPE)

1/13/2025 04:57:31 pm

Just wondering
Q. What are those things that look like ducts with
lots of holes?
Maybe cable trays?

Clear example of Architects or Others more concerned with appearance than function!

I'm working with a winery client in the boondocks,
who is concerned with the slope of the roofs on a series of corrugated steel fire water tanks.

Donald Pierce link

1/15/2025 12:06:23 pm

One more comment: This ceiling is not static. The living, growing plants not only have the potential to obstruct horizontally but vertically. Sprinklers above and below and be mindful of small hanging obstructions that could become significant.

Sprinklers Required Below Mesh Green Ceiling?

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