Hanging Issues in Attic

[MechEng2007]

Hi - Thanks in advance for any help on this issue.
We have a 4" pipe feeding back-to-back attic sprinklers in an attic with standard 2x4 roof trusses; the pipe will be running perpendicular to the trusses. What is an acceptable method to hang this pipe per NFPA 13 (2022 edition)?

Option 1: Per 17.2.4.3 - Install 2.5" Wood Sammy's into the bottom (vertically) of the top chord 2x4 every 14 ft. Wood Sammy Model is GST 25-380 (

http://fastening-solutions.itwbuild...ys-3-8-vertical-threaded-rod-anchor/8009925).

Is this acceptable and am I using the correct code reference?

Option 2: Per 17.2.4.3.2 - Install 2" Wood Sammy's into the side (horizontally) of the top chord 2x4 every 10 ft. Wood Sammy Model is SWG 20 (

https://www.confast.com/product-sammys-3-8-horizontal-threaded-rod-anchor-swg-20-8021957-25-box/).

Is this acceptable as well?

General Question: Does NFPA 13 ever permit the use of a Wood Sammy with a 1/4" screw size? I cannot see that they do.

The local AHJ is quizzing me about which section of NFPA 13 permits the hanging method I want to use.... I have a feeling he knows I am making a mistake which is very possible. Looking at the details and figures in the Sammy catalog and reading NFPA 13 has me second-guessing myself about which method, if any, is acceptable.

 

[Danefre]

That's odd that the AHJ is questioning this. Every wood construction building we've done, we've used SAMMYS as you describe, and as permitted by the listing.

SAMMYS are UL listed and FM approved for those loads (4" pipe). Check out the GST30

The section you're looking for is 17.1.6.4. Other fasteners shall be permitted as part of a hanger assembly that has been tested, listed, and installed in accordance with the listing requirements.

The dimensions of the trusses you are describing also comply with these requirements.

If the question is, "can the trusses support this load" then get a structural engineer involved. That's beyond our scope.