Irregular-Room Spacing Apply to Only One Wall?

3/25/2024

Hello, First post for me here, thanks in advance for the assistance.

In regards to the irregular room and spacing off the walls, I understand the .75 allowance up to 11'3" for the irregular or less than 90 degree wall (NFPA 13, 2019, 10.2.5.2.2).

However, I have a set of plans I'm reviewing showing four rooms with only one sprinkler and they are applying this section as one wall in each room is irregular - however - the other walls are all regular 90 degree walls but they are exceeding 7'6" off those walls as well.

In my interpretation, they should only be able to apply the above section for the irregular walls only, not normal 90 degree walls.

In this situation I would request an additional head in each room.

Am I missing something here?

Thank you.

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9 Comments

Glenn Berger

3/25/2024 08:22:07 am

IMO, you are correct. The irregular room rule should only be utilized as required and not as a carte blanche rule.

J GOLDEN

3/25/2024 08:32:32 am

The other "small room" rule allows up to 9' but only off of 1 (one) 90-degree wall.

"The small room rule can be stated as: In a room of 800 sq. ft. or less, having unobstructed ceiling construction, and light hazard contents, sprinklers may be located up to 9′ from any single wall with the maximum area of coverage being determined by dividing the size of the room by the number of sprinklers.

To apply the small room rule, the space must meet all the requirements of a small room as defined in NFPA 13. A “small room” (NFPA 13:3.3.22) is a space that is classified as a light hazard, has unobstructed ceiling construction, and is no greater than 800 sq.ft. Application of the small room rule will affect two critical system design elements, maximum area of protection and sprinkler spacing."

Jack G

3/25/2024 08:44:40 am

Agree with above.
Small room if applicable.
If not and as originally described must addasprinkler.
Opinion— err on side of caution, for safety’s sake.

Dan Wilder

3/25/2024 08:52:15 am

This would be a great time to post a photo of the room if you can get Mr. Meyer to upload! I tried the ASCII way and it did not end well LOL.

Initial thoughts are they are applying small room rule to one wall and using the irregular shape room allowance for the other side which would be allowed IF all the rules were followed for both instances...so being 9' (measured perpendicular) to more than one wall would not be allowed, the SxL is followed to not exceed maximum square footage (225ft² for the sprinkler and 800ft² for the room), being no greater than the 11'-3" AND not exceeding the 7'-6" from the 2 irregular walls. It would boil down to the actual layout and dimensions, but it could be done in some cases.

NFSA EOD - October 2014 #12 13-2013 Edition
https://nfsa.org/2020/12/01/the-nfpa-13-small-room-rule-frequently-asked-questions/

Jesse

3/25/2024 09:55:28 am

Would love to see a photo or a sketch of the irregular shape. The small room rule may apply which will allow 9-0 spacing of a standard coverage sprinkler off of one wall

Dave

3/25/2024 11:01:12 am

Note that the 11'-3" spacing is not off the wall of the irregular area, but to any point of the floor area (see the diagram in the annex). I assume these are not extended-coverage sprinklers. My initial reaction is that there is nothing wrong with a properly applied small-room rule used in conjunction with this allowance for an irregular corner of the room if the perpendicular spacing off the other walls is not exceeded.

Chris Heyer

3/26/2024 08:42:33 am

Thank you all...I'm going to try to post a quick sketch shortly

MODERATOR

3/26/2024 10:13:14 am

A sketch of this situation has just been updated on the original post. See it here - https://www.meyerfire.com/daily/irregular-room-spacing-apply-to-only-one-wall

Thanks everyone!

3/26/2024 02:29:32 pm

I do not agree it would be a good idea to use two code references that reduce coverage in one room to save one sprinkler head. If that room became a storage room due to it's odd shape, which it more than likely will be, then it is way under protected. IMO

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Irregular-Room Spacing Apply to Only One Wall?

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