Is flashing over a sandwiched deck beam really needed?

Old 05-04-16, 08:12 PM
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Location: NY
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Is flashing over a sandwiched deck beam really needed?

I'm building a deck at the moment in the northeast. I have passed framing inspection today. I have a beam consisting of two above ground PT 2X10 sandwiched together sitting on a notched 6X6. Joists already attached.

It occurred to me this morning, after I had already completed framing (no decking in yet) that the seam in the beam could take in water and then the deck will really struggle to dry out the beam, particularly since I'll be painting one side.

I see a lot of people "online" are flashing their beams, but the inspector today when I asked him if people do that he said no (so obviously most around here don't bother), and I see a ton of videos/pics online of people who haven't.

I think best practice is to do it (can't hurt, right?), but to do it at this point I'd have to unscrew the joists from the beam, temporarily lift them up a few mm, and put something in place. I think caulk would be worthless as in a year or two it would be cracked around the edges anyway.

I also cannot find a single picture online of an actual deck beam sandwich of two PT pieces rotting from the middle.

This doesn't mention it, either:

Is it worth the effort? If not, is it worth the effort to take some of the roofing felt I have and staple it at least between the joists to minimize the wetting on the beam? Sometimes I get caught up in really stupid minutia when building and this is starting to feel like one of those times
Old 05-04-16, 08:52 PM
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I built a second story deck, also in NY, according to an architect's plans which included doubled 2x10s. There was no concern about water getting trapped between them. BTW, the deck survived Hurricane Sandy.
Old 05-04-16, 10:11 PM
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I've only seen it done once and all they did was lay a strip of tar paper over the top and nail it in place.

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