Can a Sidewall "Skip" A Beam Pocket?

3/3/2023

Since sidewall sprinklers must be installed below smooth, flat ceilings, when I am confronted by beams installed perpendicular to the wall in which sidewall sprinklers are installed, I always install sidewalls below the smooth flat ceiling of each beam pocket.

My challenger suggests that if the "Obstruction Along Wall" rules of NFPA 13 Figs. 10.3.6.1.4 (2019 ed.) / 8.7.5.1.4 (2016 ed.) for standard spray sidewalls is met* then you can "skip" a beam pocket if the overall spacing and coverage is met.

Can you skip a beam pocket with a sidewall?

My opinion is that these are not intended for continuous obstructions such as beams, which adversely affect heat collection.

Y'all on my side?

*or the relevant figures for extended coverage sidewalls, or via the MeyerFire Sprinkler Obstruction Tool are met

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11 Comments

Anthony

3/3/2023 06:45:42 am

I think this falls the "smooth flat celling" test from the get go. The rules of 8.7.5.1.4 deal with single non regular obstructions. like a duct running through the area.

Jesse

3/3/2023 08:10:15 am

On the face of it, I think so. But I'm curious as to how deep beam pockets are.

Glenn Berger

3/3/2023 08:12:41 am

Dimensions are needed to evaluate and advise.

Anon.

3/3/2023 10:39:11 am

Thank you, in the example being presented, the beams are W16's, ranging from 7'-6" to 8'-0" spacing. The designer placed the sprinklers intending to comply with the sidewall obstruction table in hopes to have sprinklers in ever other pocket, spraying EC sidewalls "under" the beams flanking each unprotected pocket. I believe this in not correct, but frankly (Franckly?) I could not come up with a solid argument that the obstruction table cannot apply.

Pete H

3/3/2023 12:42:42 pm

If they're considering EC sidewalls to spray under the beams, Table 8.7.5.1.4 (2016) does not apply. EC sidewalls are governed by Table 8.9.5.1.4 (2016)

Dan Wilder

3/3/2023 08:40:23 am

Based on the restrictions for obstructions when using sidewall sprinklers, I would be very interested what the dimensioning is for the beam pockets that would allow skipping.

Considering a pan deck with fluting greater than 3" is no longer considered smooth/flat, Section 10.3.2 (13-22') negates any light or ordinary hazard use in that case. That same approach could easily be applied to any sort of closely spaced beams with sidewall protection when skipping pockets.

I suppose lowering the sprinkler to 12" below the deck would allow some specific depth of beams to extend from the wall the sprinkler is attached without being an obstruction but there is no provisions for ceiling pockets with sidewall sprinklers.

I see a lot more inferences & reasons to not allow it and this reminds me to bring in my EOD handbook.

Anon.

3/3/2023 11:05:25 am

Dan, it is T&G wood decking on 16" deep wide-flange beams, beams are at 7'-6" to 8'-0" spacing.

Pete H

3/3/2023 12:41:42 pm

If the obstruction comes from the same wall as the sidewall sprinkler (which it seems to as this did claim they were perpendicular), as long as you meet the spacing requirements of Table 8.7.5.1.4 (2016), you're protecting the floor past the beam.

You described a 16" beam. Assume you have standard coverage horizontal sidewalls so you can be a maximum of 12" below deck. Now we have a difference of 4" between your deflector and the bottom of the beam, provided your sidewall heads are no more than 14'-0" apart for light hazard and 10'-0" apart for ordinary hazard, and are the required distance from the beam, you're okay.

That said, looking at the thread I think you've used those letters "EC" and extended the coverage of the sidewall. Now 8.7.5.1.4 doesn't apply (where you only needed to be 2 feet away to spray underneath the >5" difference between deflector and bottom of the beam) BUT go to table 8.9.5.1.4 for extended coverage sidewalls. Now to spray under 5" below deflector, you need to be a minimum of 4 feet off the beam.

Also the EC sidewall head may not be able to go a full 12" below deck/ceiling, check the listing to see what applies. And a vertical sidewall head is right out (as even standard coverage peaks at 6" below ceiling and would add 6" in difference between deflector and bottom of obstruction.)

It being a continuous obstruction is not an issue, as 8.7.5.1.4.1. provides the differentiation between isolated obstructions, to show us Table 8.7.5.1.4 is meant for continuous obstructions.

Jay

3/3/2023 02:28:57 pm

See application of sprinkler types.
This is from the 2016 Ed. A beamed ceiling is not considered a smooth and flat ceiling.

8.4.2 Sidewall Spray Sprinklers.
Sidewall sprinklers shall only be installed as follows:

(1)
Light hazard occupancies with smooth, horizontal or sloped, flat ceilings

(2)
Ordinary hazard occupancies with smooth, flat ceilings where specifically listed for such use

(3)
To protect areas below overhead doors

danefre

3/6/2023 01:37:01 pm

Hi Jay,

I would have to disagree. Sidewalls can definitely be used in obstructed construction. Check the definition of "smooth ceiling". It refers to the surface of the ceiling itself - nothing to do with beams. LIke Dan mentioned, if the corrugation was deeper than 3" then it would not considered be smooth.

This is different than "smooth ceiling construction" which is a sub-type of unobstructed construction.

Hassan Omar

3/14/2023 09:58:59 am

I have a situation where it is 2'-9" deep for ceiling pocket in which the surface itself can be considered smooth ceiling. The dimensions are 13'-6" x 13'-6" and it is a light hazard, can we use a sidewall for every ceiling pocket installed 6" or per manufacturer deflector distance?

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Can a Sidewall "Skip" A Beam Pocket?

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