Why Not Metal Deck Attachment for Pipe Over 1"?

2/18/2020

There is a confusing discrepancy between NFPA 13's ban on hanging 1.25" and greater pipe to bare metal deck versus the availability of UL listed anchors with a test load of 850 lb (that is the number for the 3/8" Sammy XP 20).

I don't understand how something that has passed such rigorous testing could be forbidden by the code. Does anybody have any background knowledge on this subject?

On top of this, I don't understand the configuration required for this application by NFPA 13. It says anchorage needs to be provided by "punching the vertical portion of the metal deck and using through bolts." (2016 Ed. 9.2.1.4.1) I don't know how to visualize this arrangement and there are no details or photos in the handbook.

Does anyone know what this is supposed to look like?

I've tried reaching out to NFPA's technical resources and have not gotten a response.

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4 Comments

Dan Wilder

2/18/2020 10:00:43 am

This was previously discussed in the thread below:

https://www.meyerfire.com/daily/hanging-directly-from-metal-deck-under-nfpa-13

This section was modified in the '96 edition (I think, or at least this is where I found this reference) that the section was added to address areas in the corners of buildings where test lines (Remote Inspector's Test lines) are run and the structure isn't there to support the pipe (where metal decking attaches to the angle iron on the exterior walls).

https://www.nfpa.org/Assets/files/AboutTheCodes/13/ROPA-1996-13-13D-13R.pdf

Page 726

Specifically it states " There are occasions in the corners of buildings, etc., when there is no structure to hang test pipes and breakarms from . This test, which is adopted from A-3-10.1 of NFPA 13-1989 will help rectify this problem. Just as with toggle bolts, sometimes there is no alternative." This was accepted in principle but was altered to be 1" not 1.5".

As for your visualization, the only thing I can think of is the small angle iron that supports the metal decking. Previous editions included a section for sheathing (which is more a vertical orientation) My opinion is that this is a hold over from that time and may need to be modified to be "Horizontal".

Nash

2/18/2020 10:38:18 am

NFPA 13-2019
A. 17.4.1.4.1
Piping in excess of 1 in. (25 mm) shall be permitted to be supported from a metal deck if the method of attachment and ability of the deck to support loads as specified in
17.4.1.3.1 are approved by a registered professional engineer.

Jonathan D Griffin

2/18/2020 11:00:03 am

Keep in mind, that the reference is not concerned that the supporting straps or bolts cannot hold the weight of the water-filled pipe; but whether the Roof Deck system is capable of supporting this load. And if so, what attachments may be utilized to attach the piping to the Roof Deck.

As you can see, a Design Professional will be required here to determine the answer(s) to your question.

Good luck!

Anon

2/18/2020 12:06:16 pm

This is worded poorly in NFPA 13 and applies to “through bolts” not other listed hangers based on the gauge of metal. 1” is not the limitation.

Why Not Metal Deck Attachment for Pipe Over 1"?

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