Why is Soffit Obstruction Rule Not in NFPA 13R?

3/19/2024

This question is regarding obstructions to residential upright and pendent sprinklers.

The 2016 edition of NFPA 13, 8.10.6.1.2 (4) states that obstructions that are located against the wall and that are not over 24 inches in width shall be permitted to be protected in accordance with Figure 8.10.6.1.2(c). This is a pretty sweet rule, as basically your only concern is the sprinkler distance from the wall and not the obstruction dimensions.

However, the 2016 edition of NFPA 13R does not contain this wonderful rule, even though the rest of the obstruction rules are essentially the same.

Any thoughts on why the decision was made not to include this rule in NFPA 13R?

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7 Comments

Pete H

3/19/2024 06:51:28 am

Since we're just giving thoughts: if I had to hazard a guess it's because in residential situations we're expecting more common other obstructions to discharge (ceiling fans) as well as this rule's necessity becoming suspect due to the shadow area allowances and sidewall heads on an opposite wall allowing for 30" deep and wide soffits.

Or they just didn't do that specific test for 13R.

It is a weird difference.

For your use... can you call the area under the soffit a shadow area and have less than 15 square feet per sprinkler in the shadow?

Anthony

3/19/2024 08:08:33 am

I think it's because residential sprinklers have a 'flatter' spray pattern so are more susceptible to obstructions protruding down from the ceiling. Also, the performance objectives of a residential sprinkler is to wet the walls to contain a fire to a compartment.

Contrasted to the more 'umbrella' shaped patterns from SSU/SSP sprinklers.

Colin Lusher

3/19/2024 08:29:40 pm

Except that the section regarding these soffits in NFPA 13 is specifically applicable to residential sprinklers only.

Dan Wilder

3/19/2024 09:19:25 am

Had to do a little digging as to the "Why"....and didn't find much unfortunately....but my guess is it wasn't submitted to the 13R Committee for approval....but.....

It is now incorporated into the 2022 Edition Figure 6.4.6.3.6.3(c). It was added to corelate with the 13 Edition under First Revision (FR)-No.14 and Public Input No.25 with no other substantiation so should be a good example of when to use the 1.4/1.6 Sections for Equivalency and/or New Technology.

https://docinfofiles.nfpa.org/files/AboutTheCodes/13R/13R_A2021_AUT_RSS_FDBallot_final.pdf - Page 44

Distance added/modified and originally rejected...
https://docinfofiles.nfpa.org/files/AboutTheCodes/13/AUT-SSI_ROPagenda_02_11.pdf - Page 65
https://docinfofiles.nfpa.org/files/AboutTheCodes/13/13_A2012_AUT-SSI_ROP_ballot.pdf - Page 98

Then accepted on the 2nd round..
https://docinfofiles.nfpa.org/files/AboutTheCodes/13/AUT-SSI_13_A2012_ROCballot.pdf - Page 83

Chris Dorsey

3/20/2024 07:27:24 am

Thank you Dan. Good to know. So I guess in a couple of decades when our AHJ adopts 2022 we'll be good to go.

Jack G

3/19/2024 02:55:03 pm

As indicated above, I believe it’s because of the flat spray.
It may have not been presented to the 13-r committee but because of all the combustible wall hangings in the typical house ,dropped soffits over kitchen islands and snack bars, over dining room tables ( like my house ) I would argue they should have them ( like my house) .
My wife quilts and we have wall hangings ( vertically) also. So no telling what is in the typical house.
Opinion.

Mike

3/29/2024 08:18:35 pm

NFPA 13 and 13R have different intents as stated in, I believe, Ch. 1. Therefore different rules.

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Why is Soffit Obstruction Rule Not in NFPA 13R?

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