Treated wood for decks

[Sifu]

Little bit of an internal debate here. Does 2018 IRC 507.2.1 require the use of treated wood for decks? I realize the option is provided in 317.1.3, but some believe 507.2.1 unequivocally requires it. My take is that that section references 317, which dictates where it must be used, and without using 317.1.3, or other specific methods, deck framing is excluded.

Don't mistake the question for my personal approval of untreated wood, I wouldn't do it, but I don't think the code provides a blanket requirement for it.

Glenn, are you listening??? I just read re-read one of your articles that strongly hints in this direction but my fellow debaters are doubtful.

 

[Glenn]

Little bit of an internal debate here. Does 2018 IRC 507.2.1 require the use of treated wood for decks? I realize the option is provided in 317.1.3, but some believe 507.2.1 unequivocally requires it. My take is that that section references 317, which dictates where it must be used, and without using 317.1.3, or other specific methods, deck framing is excluded.

Don't mistake the question for my personal approval of untreated wood, I wouldn't do it, but I don't think the code provides a blanket requirement for it.

Glenn, are you listening??? I just read re-read one of your articles that strongly hints in this direction but my fellow debaters are doubtful.

Being one of the folks that developed these deck codes, I can tell you the intent was absolutely that all deck structural wood must be treated or naturally durable. In working on my deck code book update right now, I realize this could be a bit more clear. However, it has been tricky to put deck specific codes in 507 without repeating the same stuff in other chapters. The deck codes are a work in progress...but then...aren't all the codes. Here are a few things to consider though.

1) R317.1.3 Geographic areas, has been in the IRC since 2000 and is pretty much screaming that decks need decay resistance.

2) The changes to the 2016 AWPA U1 standard added a U4CA commodity category that is pretty much scream that ALL decks need GROUND CONTACT.

3) The IRC trumps the AWPA in section R102.4.2 so ground contact is not required. But notice that both R317.1.3 and the AWPA U1 speak to creating conditions of inhibited drying where ground contact-like conditions are created. A deck has many places of contact between wood members where drying is inhibited. I just posted a photo to my social media showing a completely rotted deck five feet above grade due to trapped moisture between beam plies. And that's in Denver where it's more arid than many other regions. (actually, it's the deck in the video thumbnail)

4) If you want the deep details of this without buying the standard and doing the research I have done, my one hour youtube is the much faster way to get it. I explain all of the above and provide the standard for you to see and read.

 

[Sifu]

Thanks Glenn, I also always believed it but when I was challenged on it I felt the code didn't quite get us there without the geographical inclusion. Interestingly. the DCA deck guide has it as a requirement. It is a little misleading to specify that the ledger must be treated (and even plastic composites), but not the rest. Seems like they could clarify that. Your work on decks has been immensely helpful, keep up the good work.