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Discussion Starter · #1 ·
Hey guys, i have a little project going in the pole barn, i want to frame in a space for painting/finishing, out of the dust of the main woodshop. anyway i was going to order some materials and the lumber co is trying to sell me 2 by 12s for the ceiling joists, they will be spanning 18' and the space above will be a storage area for personnel belongings, no live weight except once in awhile to look through the old crap collection. so what do you all think about 2 by 6, 2 by 8, or do go all the way to the 2 by 12's? the old framing book i have by Larry Haun says a 2 by 6, doug fir #2 or better can span 19' 11" if on 12" centers, or 17' 9" if on 16" centers....so whatdoya think? and thanks for looking. rf
 

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I agree with that being undersize. We never span anything that long with 2x12. My house 2 x 12 subfloor is maxed out at 15 ft and the only thing sitting on it is furniture. If you build it, you will load it up. I would suggest 16 inch wood I joists. I guess the local building department doesn't have an opinion on it. lol
 

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why don't you like tjis. lvls would be very expensive to frame a whole floor. We have done it but it was quite expensive, but only solution at the time that the engineer would approve.
 

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muskoka guy said:
why don't you like tjis. lvls would be very expensive to frame a whole floor. We have done it but it was quite expensive, but only solution at the time that the engineer would approve.

Burn rate. Im a fire fighter.
 

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I'd use lvl only because I don't like TJIs
I don't care for TJI's either. I'm probably wrong, but I don't see how a 2X2 sandwiching a piece of plywood is stronger than a 2X10, by which we've seen them last for decades. I'd still give credit for the guy who invented TJI's if they were or were not.


But anyhow, if it was my own project, I'd trust 2X12's @ 18' for this span. Maybe if he can add some blocks or something to help prevent sagging might help.
 

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ObuckiO said:
I don't care for TJI's either. I'm probably wrong, but I don't see how a 2X2 sandwiching a piece of plywood is stronger than a 2X10, by which we've seen them last for decades. I'd still give credit for the guy who invented TJI's if they were. But anyhow, if it was my own project, I'd trust 2X12's @ 18' for this span. Maybe if he can add some blocks or something to help prevent sagging might help.

He'd probably be fine with 2x12s but he did ask if he could use 2x6s
 

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So, you have the link to the span calculator, but you're still not informed about live loads. Attics should be designed to hold a MINIMUM 20 lbs / sqft live load. I think SYP and doug fir get you there on a 2X12, but run your numbers and see.
 

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I've been surprised at some of the things I seen smaller wood hold up that we all would frown upon.
If deflection doesn't matter, sizing goes way down even with an acceptable safety factor. Driving the front of a front wheel drive car on 2X10 SYP boards supported on the flat at points 6' apart is outside any loading you'd go with in building, but I've done it plenty of times.
 

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Do you really want to put 2X6s on 4" centers? If you halve the depth. you need roughly 1/4 the spacing.
 

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Discussion Starter · #18 ·
Ya your right i should use 2by12's and feel OK about sending my wife up there to dig thru our old crap once a year.
 

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I have seen similar lofts loaded with lumber. You are a cabinet maker, you can bet some is going to get up there. If you go too light it will sag. Even if you don't plan on loading it, someone else in the future might.
 

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Thanks for the information guys, i am a cabinet maker so ya i am a little uninformed about loads.....but ya'll have helped enlighten me, i guess i'm wondering if you could use [email protected]"centers why not [email protected]" or 8"...wouldn't you get the same strength? rf
Bending strength is roughly the board width cubed so a 2x12 is around 8 times stronger than a 2x6
 
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