Is Horizontal Screen an Obstruction to Sprinklers?

5/2/2022

I have a laboratory space which original had an open ceiling. The renovated space plans to provide a screen, similar to a window insect screen across the open ceiling, which will contain lizards which they are working with.

Is this screen considered an obstruction to the sprinklers above?

The screen would be located approximately 3-feet below the main ceiling at 8'-0" above the floor. Although water would pass through, it seems that it would significantly disrupt the distribution pattern from the sprinklers.

This also does not seem to meet the requirements for an open-grid ceiling. Thanks in advance.

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8 Comments

Alex

5/2/2022 07:48:23 am

Hi,

This is a good question. I'm sure we will see differing views on this issue in regards to open ceilings versus other horizontal obstructions. Hopefully today, someone can cite a code section that puts the issue to rest!

On one hand, you have NFPA 13 (2022) 9.5.5.3 that states that horizontal obstructions that interrupt water discharge shall comply with 9.5.5.3 and the following subsections.

9.5.5.3.1 states that any obstruction over 4 feet require sprinklers installed beneath.

The annex material states that for slat decks, walkways, or open grating, the use of opening or enlarging the openings are not a substitute for automatic sprinklers. If you go this approach, I would say you require sprinklers beneath your screen no matter your percent open.

On the other hand, the code doesn't call out this specific scenario. Nor will it ever (there are far too many scenarios out there)! Think of providing a screen above a storage compartment within an apartment complex. The screen is installed to prevent storage being stacked too high, thus obstructing sprinkler discharge. But then do you need to install sprinklers beneath the screen? I would say no!

So if you are looking at it this way, I would say treat it like an open ceiling. NFPA 13 (2013) 8.15.14 states to have the screen 70 percent open. Personally, this is how I would prevent sprinklers beneath.

In the end you state that you do not fall under the requirements to be 70% open. Therefore, I would say you do need to install sprinklers beneath the screen.

Thanks,
Alex

Jesse

5/2/2022 08:13:48 am

This is a tough one. The screen will disrupt development of the spray pattern. However, sprinklers underneath the screen probably won't collect enough heat to activate.

I think it does indeed pose an obstruction. I would recommend protecting using either horizontal sidewalls with a heat collector (depending on room size), or regular pendents with heat shields.

5/2/2022 09:54:43 am

No disrespect intended, but "heat collectors" are proven not to work, and are now specifically prohibited in NFPA #13: "Heat collectors shall not be used as a means to assist the activation of a sprinkler. (See also Annex commentary.) Furthermore, sidewall sprinklers shall only be installed beneath smooth, flat ceilings.

5/2/2022 08:23:36 am

I would send an RFI inquiring about how open the screen is. If it's 70% open or more (you can figure this out by doing some simple math that I would recommend showing on your drawing), then I would follow NFPA 13, 2016 8.15.14 for Open-Grid Ceilings. If the screen is not 70% open I would put the decision in the A/E teams hands regarding changing the screen to a screen that is 70% open or adding an intermediate sprinkler with a water shield below the screen to provide above and below protection. I don't think you're going to find this specific situation in NFPA 13, but an Open-Grid ceiling is probably the most similar concept to what you are describing.

Dan Wilder

5/2/2022 08:24:20 am

What's the material? Anything not metal will likely burn away near the fire location anyway. If it is metal, there may be a stronger point for a water shield and sprinklers beneath.

Are they putting any additional "plants" above (Live or dead)? At best (or worst depending on how you look at it), this looks more like a Rain Forest Café to a point but if this is occurring, those locations of "plants" may be your best bet for a lower sprinkler location with a water shield.

Open-grid ceilings have a specific minimum opening, typically 1/4", and have the ability to prevent the sprinkler pattern from developing horizontally. Being 36" below, you could make an argument for a smaller spacing layout to alleviate the spray pattern disruption. An example would be an F1FR56 sprays about 4.5' horizontally at the 3' mark (at 7 PSI) so an 8x8 sprinkler spacing removes the gaps potentially created by the screen. An approach you could talk with the AHJ about as an AMM.

Hunt

5/2/2022 09:17:29 am

Good call.. The screen material and percentage of openness needs to be identified first. Possible deluge?

Glenn Berger

5/2/2022 08:40:24 am

Potential Obstruction - yes, depending on the material and the openness of the screen material.

franck

5/2/2022 04:21:19 pm

As indicated by Dan, if the material is combustible (plastic for example), this is not a problem as it will burn quickly so that the sprinkler above can operate without problem

I made of metal (or even wood, as it will remains for a ling time), this could create an obstruction and should be considered as such.

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Is Horizontal Screen an Obstruction to Sprinklers?

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