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Old 02-28-2011, 11:41 AM   #1
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Sizing GluLam

Am building a 36' X 33' two story barn. Am using two 2X12X20's slammed together to make a 33' joists but I suspect that the joists will bow over time and need to add some support. Am thinking that a glu lam or two running accross lenghwise (36') might do the trick. I need the barn space below to be free of obstacles (no posts). So the ceiling will need to be suspended and supported only by the outer walls. Any thoughts on the size and thickness for glue lams running suspended 36' and supported only at both ends?


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Old 02-28-2011, 12:08 PM   #2
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What did your structural engineer tell ya?


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Old 02-28-2011, 12:16 PM   #3
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The manufacturers have engineers who do the calculations. Just download the brochure and look up size.

Or go to a "real" lumber yard and they have a computer program that will size them.

My rafters span 16 feet. There are 22 feet of rafters. We installed a pair of 2 inch by 16 inch beams, 22 feet long. I think one of them might have worked for what we wanted, but the software said two. I think they were under $500 for the two, delivered. They're really heavy! It was a chore for the two of us to get them up and in place. Don't let a finger get between an 800 lb. beam and a rafter.
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Old 02-28-2011, 12:56 PM   #4
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You are using two 2X12X20's slammed together to make a 33 foot joist. I have no idea what you are talking about, the last time I saw something like that was at a Depeche Mod concert in the mosh pit. I mean, did you shoot the two beams at each other?

I assume you are working off plans, this is a rather large structure to be winging it. If you are not working off plans, well getting structural advice off an internet chat board is a pretty rough substitute for some serious engineering. If you are working off plans, and you think they are inadequate, it might be a good time to hire a structural engineer or architect to review them. Sizing 33 foot spans by guesswork is dicey at best, could be fatal at worst.
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Old 02-28-2011, 01:09 PM   #5
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For tech info on glu-lam beams and any other sort of engineered wood, the go-to source for the most reliable information is the industry association, . If you visit their website, you'lkl find all sorts of articles and dowloadable PDFs with schematics and so forth, available for free.
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Old 02-28-2011, 03:40 PM   #6
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Steel beams, and even then you'll need posts.
I wouldn't even build a doghouse with 2-2x12 beams "slammed" together!


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