Treated lumber for shed or not?


Old 10-20-09, 04:41 AM
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Treated lumber for workshop or not?

Hi there,

I'm new to the forum, but I've read some good posts (questions and answers). I'm looking to build a rather large shed/workshop (probably 16 X 24 or 16x 30). I'm planning on making it on a deck foundation (instead of a real poured slab with a real cender-block foundation), since it's on a decent slope. One side is about 6 inches off the ground, and the other edge is probably 5 feet or so. That's way too much $$ for doing it the right way.

Now, should I use treated joists with this workshop, and/or treated plywood? The only reason I'm asking is pure $$. It's about twice as expensive as non-treated here (I guess that's probably true everywhere). The way my joists are running, it's possible for me to start out with the first 3 or 4 treated, and then go with non-treated for the rest of them, but don't know what I should do.

I obviously don't want it to rot (going to have all my tools and such in it), but I'd rather make it as cheaply as I should, as I don't have THAT much spare money. However, I want to build it to LAST.

What are your thoughts? Thanks for letting me in your forum.
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Old 10-20-09, 06:17 AM
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I would use treated for posts, joists, and floor. Then non-treated the rest of the way up.
Old 10-20-09, 06:22 AM
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I was thinking that orginally, but then I saw a couple of articles that said that treated lumber was intended for "ground contact" applications. Therefore, if the shed was a couple of inches above ground, they would still use it. I think they said something about 12" above the ground as the general rule of thumb. Anything above 12", they'd use common lumber, below 12", and they would use treated (joists, floor, etc.). They said something about the amount of air flow between the ground and the 12" span....

That's why I'm posting here. I don't know if that's a general rule, or just someone's opinion. I wouldn't mind saving a couple hundred bucks, but don't want it to rot after a couple of years.

Thanks again!!
Old 10-20-09, 09:51 AM
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what about termites/carpenter ants,in your area?
Old 10-20-09, 11:12 AM
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Not that I'm aware of....haven't seen many in the mulch around the house.
Old 10-20-09, 11:27 AM
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Hi Tim, Make sure your code people will be happy. As far as treated vs untreated, have you looked to some of the treated decks that set several feet above the ground. They fall apart over time, and those are treated. The bigger issue is covered or uncovered, or exposed to the moist air. Treated will far outlast regular wood when exposed in any way, so I agree with wirepuller, posts, joists, and floor. You could option for some osb flooring that is rated for exterior, if there is a price difference.

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