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Building a durable deck

I'm looking at building a small free standing deck, perhaps 200 square feet or so. It'll be pretty low to the ground, less than 30 inches for sure. It seems to be widespread practice now to put rubber flashing on top of the beams, joists, and on joist ends, to protect the tops and hanger joint from water.

I'm wondering if maybe that can be taken a little further for minimal cost and improved rot-resistance. How about wrapping the sides of beams/joists, maybe even the bottoms too? Perhaps with poly or felt or housewrap -- would it be better for it to be vapor-permeable or not? Has anyone tried this? Is it a stupid idea? I plan on living in my home for decades and I'd appreciate not having to replace the deck framing in the future just because of some silly preventable rot.

Asked by Nick Welch
Posted Thu, 07/17/2014 - 19:15
Edited Thu, 07/17/2014 - 19:16

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6 Answers

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1.
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Nick,
Wrapping anything other than the places you initially list would be counter-prodiuctive. The membrane is there to stop moisture from getting into, or providing a buffer between, structural members where they meet and where moisture accumulates leading to rot. The sides and bottom of the beams or joists need to be able to dry. I'd do a diligent job over the beams and joists and let air flow do the rest.

Answered by Malcolm Taylor
Posted Fri, 07/18/2014 - 00:17

2.
Helpful? 0

Nick,
I agree with Malcolm. Leaving the sides and bottoms of these framing members exposed to the air encourages rapid drying.

If you want to perform an experiment, try this: Take two stacks of firewood (with equal volumes of wood in each stack). Cover the top of the first stack with metal roofing held down by rocks, while leaving the sides of the stack open. Wrap the second stack in polyethylene on all sides. See which stack of firewood dries the fastest.

Answered by Martin Holladay, GBA Advisor
Posted Fri, 07/18/2014 - 06:11
Edited Fri, 07/18/2014 - 06:13.

3.
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If you plan on living at that location for an extended period of time, you might consider a patio instead of a deck, especially if it's low to the ground. I've had several of both, and patios win hands down IMO, with a lot less maintenance. And low decks are the worst, as it's difficult to under the deck to spray the bees/paper wasps/etc that seem to love living on the underside of decks. And of course there's always the skunks...and opossums...

It seems that all the nice decks that I've seen are brand new. It's possible to build one that looks good for a long time, even when subjected to full sun or full shade, but I haven't seen many (actually, any) in real life.

Answered by andrew c
Posted Fri, 07/18/2014 - 10:56

4.
Helpful? 0

Andrew, I was avoiding going there but agree entirely. Decks are perfectly designed to bring disappointment into our lives.

Answered by Malcolm Taylor
Posted Fri, 07/18/2014 - 11:40

5.
Helpful? 0

I've briefly considered a patio, but I'm way less confident in my ability to pull that off accurately, and preparing the base seems like miserable work. Pain now or pain later? It's hard to decide.

Answered by Nick Welch
Posted Fri, 07/18/2014 - 14:18
Edited Fri, 07/18/2014 - 14:18.

6.
Helpful? 0

Nick,
After facing the same dilemma several times I now build a sort of hybrid. If you use PT lumber and incorporate the membranes you are considering the deck structure will last a long time. This still leaves the decking itself. I now strap the joists with PT 2"x4"s at 12" o.c. and lay patio stones. It does add somewhere around 20 lbs a foot dead load but leaves you with a virtually maintenance free surface. There are a number of proprietary systems that do the same thing but I've found the strapping works just as well.

Answered by Malcolm Taylor
Posted Sat, 07/19/2014 - 12:10

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