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paulz
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# Posted: 25 Sep 2019 05:50pm
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I'm commencing building a carport on this old concrete structure on my property. It's an interesting story I'll explain later and post better photos. My plan is a plywood roof with tar or torch down, mild slope, no snow.
I salvaged 30+ of these engineered joists, and a half dozen parallam beams out of a warehouse demo a few years ago with this in mind. They are 18" high, the span will be 20'.
It will not be enclosed. It's in dense forest, very damp winters with little to no sun. I'm concerned about the durability of these joists. I have 20' 2x12 regular boards I could use instead but that leaves me with the I-joists. What do you think?
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rockies
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# Posted: 26 Sep 2019 08:14pm
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I was reading on a construction site that I joists are basically mold food. In a warm, dry environment they work well but I don't think they would last long in a damp, dense forest.
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paulz
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# Posted: 26 Sep 2019 09:26pm - Edited by: paulz
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Thanks rockies, we'll I guess I'll see, started laying it out today. I did some reading too, they are used a lot in above ground flooring, as long as you keep them from getting wet they seem to do OK. The main thing I realized is that I have stored them for two or three winters stacked right on this concrete under a tarp and they haven't suffered. Can't imagine it will be any worse in use. I have agonized for over a week on using them or not. See those 4 ladders? Bet I went up every one a dozen times today. 
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Aklogcabin
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# Posted: 27 Sep 2019 10:46am
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I think you’ll be fine. I used them on a garage I built a couple years back. So going on memory here. I believe you can go to BCI 60 series you can find out. But I believe the dead load was 60# and live load 40#. On a 20’ span. Also allows for r38 insulation and several inches for air flow.
They do recommend specific hangers or tie downs and nailing patterns. Also specific ways to construct overhangs and blocking.
The laminated beams use waterproof glue.
And I would use them over twisting 20’ pieces of lumber any day.
Good luck on your build.
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paulz
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# Posted: 27 Sep 2019 12:13pm
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Thanks Ak, that's reassuring. Yeah I have the special joist hangers, have read about all the special blocking etc. these take. Bit of a bother but I think I have it covered.
I'm thinking about using screws in the hangers. Generally it's a no no but I guess they make special screws for joist hangers. Still studying up on that. More layout to do first.
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Brettny
Member
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# Posted: 27 Sep 2019 01:09pm
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You could always stain them for a bit of protection. If your seeing mold start spray the whole area with 50/50 white vinegar/water.
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rockies
Member
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# Posted: 27 Sep 2019 08:55pm
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Here's a study that may help. Check the info under "conclusions".
https://pdfs.semanticscholar.org/7cfe/fe2d5eb9b6d74b168832b7ee0d680d4bfe30.pdf
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ICC
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# Posted: 27 Sep 2019 09:57pm - Edited by: ICC
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Were not the i-joists in that study exposed to direct rainfall not just high humidity? That said, I'm still not sure I like them for use in a non conditioned space. But if they were stored for years (under cover?) and have no mold showing, I might spray paint them with a kliz primer that has mildew resistance. If mold or mildew has already taken hold anywhere I would landfill them. Just my thoughts.
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paulz
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# Posted: 28 Sep 2019 11:12am
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No mold on them at all but great idea on spraying with a preservative. I better check and make sure that's kosher. I had them stored under one of those tube frame and poly tarp canopies with another poly tarp directly over them. One or two did get wet and are stained but seem ok, hopefully won't need them.
Been debating 16 or 24 centers, not sure I have enough for 16. I could put another beam halfway out, trying to avoid it. 5/8 plywood going on top.
Thanks again for the advice.
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