In a coastal climate with rain can I use untreated beams for an exterior deck if the deck has a torch on membrane?
The deck sits on a retaining wall to provide a 4' crawl space. The crawl space may just be a gravel floor with a vapor barrier.
Considering a 5.25"x11.78 PSL @ ~18'
I did some research and their is a PSL plus which is treated and carries a 30 year warranty for exterior use. The lumber yard doesn't typically carry it and the manufacturer has all products to this yard on a 6 week backlog or something.
The lumber yard is telling me that they can send out a standard PSL or any structural member for pressure treating and for the beam as specified it would ~$100. The standard PSL subjected to pressure treating isn't going to carry the 30 year warranty and I don't have a good way to determine how much better the Weyerhaeuser PSL plus is going to be over a Weyerhaeuser PSL treated in a chamber even if they use the same stuff - probably I'll give their tech line a call and see what they think. $100 is nominal so if I can't get the PSL plus I'll go for the manually treated PSL as it seems like as long as I have adequate venting even a standard PSL would meet code.