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WILL1E
Moderator
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# Posted: 1 Feb 2021 09:28am
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Why would I or wouldn't I use I-joist vs solid lumber for my elevated floor system or even my shed style roof for my cabin build?
Cost per linear foot is within cents of each option, however i-joist span ratings for the equivalent size is far stronger than solid lumber.
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Nate R
Member
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# Posted: 1 Feb 2021 09:46am
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I joists are VERY specific in what you can do in the webs. Just make sure you know what's allowed as far as holes, etc. If it's fine for your situation, no problem.
Different joist hangers needed for I-Joists.
They don't hold up as long in a fire, some say/fear/claim. A risk to firefighters, mostly.
Yeah, tough to say which to use. I like sawn lumber, but hard to argue with i-joists in a lot of ways.
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Irrigation Guy
Member
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# Posted: 1 Feb 2021 10:48am
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Do t let them get too wet
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Brettny
Member
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# Posted: 1 Feb 2021 11:01am
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Shed style roof..how do you plan on attaching them to the top plate? I dont believe you can put a birds mouth in them.
How wide of a building are you making again?
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WILL1E
Moderator
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# Posted: 1 Feb 2021 11:12am
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Quoting: Brettny how do you plan on attaching them to the top plate?
I found these as an option.
Building will be 16"' wide and 20-28' deep (TBD).
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paulz
Member
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# Posted: 1 Feb 2021 11:22am
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Used them in half my shop roof, just because I got them for $300 out of a warehouse demo, including the beams. 20' span. The front half is 2x12, 14' span ($400, out of a church demo).
They are a more trouble to work with, harder to cut, need support blocks at the ends. Not sure how well the composite wood holds up to moisture.
On the plus side they straight as a bear's dick, no flex at all, lighter. I figured I could put a building on top of mine, not that I ever will.
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Irrigation Guy
Member
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# Posted: 1 Feb 2021 11:38am
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Quoting: paulz On the plus side they straight as a bear's dick
How straight is a bear’s dick? Asking for a friend.
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Brettny
Member
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# Posted: 1 Feb 2021 11:41am
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Quoting: WILL1E found these as an option. Building will be 16"' wide and 20-28' deep (TBD).
Didnt know they made such a bracket. That would add $10 per rafter...for what benefit? 20' lumber is available at big box stores and needs no special brackets.
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NorthRick
Member
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# Posted: 1 Feb 2021 07:03pm
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Quoting: Brettny Didnt know they made such a bracket. That would add $10 per rafter...for what benefit? 20' lumber is available at big box stores and needs no special brackets.
Yeah, but how about straight lumber?
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ICC
Member
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# Posted: 1 Feb 2021 08:14pm
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Factory-made joists and assorted trusses really come into their own place when the buildings get larger than the typical small cabin.
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Brettny
Member
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# Posted: 2 Feb 2021 07:24am
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Quoting: NorthRick Yeah, but how about straight lumber?
I have had better luck buying straight lumber from a smaller lumber yard. I even got quite a few no1 boards for my last project. Even the no2 are better than what big box stores sell. And to top it off the local yard was cheaper in everything (even plywood) except for 2x4x8'
Believe me I hear you on finding streight boards at big box stores too. I did a major reframing job on my house and after we filled the 7 lumber carts it had looked like a bomb went off in the homedepot lumber section.
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Aklogcabin
Member
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# Posted: 4 Feb 2021 10:20am
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Manufactured beams work very well. Nice thing is you can get any length you want. They stay straight. Use moisture resistant glues. Light weight. One guy can easily handle 24'ers. I've used 16" tall beams to span 24' for my garage. And provide plenty of airflow above the r-42 rockwool insulation. Easily meets code for AK winters snow load. Easily nailed down. They come with knockout plugs that utilities can run through . I used 16'ers on our cabin floor very solid.
Since I had to haul freight over several years they sat under a tarp for a few years. They are still looking new.
I would highly recommend them.
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WILL1E
Moderator
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# Posted: 4 Feb 2021 10:52am
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Couple more questions regarding i-joist:
-Does the 2.5" width at the top and bottom mess with insulation widths or anything like that?
-When used as rafters on roofs (in my case, a single pitch shed style roof), what would be the best way to handle the eaves? Cut the I-joist flush with the walls and scab on hand built eaves or just run the i-joist past the walls like traditional eaves and then be sure to box them in?
-If i use i-joist for the above mentioned roof, would i just use standard lumber for the last rafter on each end to build the gable ladders?
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snobdds
Member
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# Posted: 4 Feb 2021 10:57am
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I used them for my loft floor so I could span 24 feet. Dimensional lumber would have needed a support post in the middle.
I see some people using them for roof rafters. But they can't be bird mouthed for a top plate and rafter tails have to be sistered on and be dimensional lumber. Then the layout gets off, a giant pain in the rear end. TGI's cannot be exposed to weather. For all that work, I would just use 2x10 for that purpose.
But for a flooring joist, they can't be beat.
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Brettny
Member
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# Posted: 4 Feb 2021 01:21pm
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Quoting: WILL1E Cut the I-joist flush with the walls and scab on hand built eaves or just run the i-joist past the walls like traditional eaves and then be sure to box them in? -If i use i-joist for the above mentioned roof, would i just use standard lumber for the last rafter on each end to build the gable ladders
Both good questions. I dont really think you want to attach anything to the ply center section nor possibly tweak the side of the i joist. You could use perlins over the joists but then you would have to put them over the whole roof.
Boxing in the eve is simple enough.
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paulz
Member
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# Posted: 4 Feb 2021 09:01pm
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I've had some trimmings sitting out in the rain for a couple of years. Doesn't seem to bother them.
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Aklogcabin
Member
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# Posted: 5 Feb 2021 12:30pm
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Hello. No the wider tops n bottoms do not interfere with insulation, actually helps hold it in . The wider top n bottom makes for more nailing surface.
When installing for roof joists. Just run them long n box in like any eve. I used 3/4" acs with exterior glue plywood for facia board for the 16" tall x 28' long joists i used on my garage. Spans 24' with 2' tail. Can't remember live or dead load but you can go to bci website n read all about them. Weight loads n construction techniques.
To attach to top plate i ripped a 2x6 with the corresponding roof pitch. In my case 3-12. With metal roof. 1/2" osb sheeting. Felt. If you're going to hang a deck off them. I install a 2x on the back side for increased holding power. Then use galvanized toggle bolts to bolt on outer rim joists for the deck. Caulk holes.
For the last joists on sides fill in the web with plywood.
When I installed them on my garage I nailed in the froz boards to the joists before I set them up. Then they would stand up on their own.
I have a 1959 International linesmans truck made for setting utility poles. It has a boom. So I could lift them up. 14' front wall, 8' back wall. I did some by myself before a friend stopped by. They make a solid laminated material for the ends for the rim joists that matches the height.
Hey let's be clear. I don't own any stock in any of these companies. I have used them for floors n roof joists very successfully.
And they are straight n stay straight. As a guy who worked as a professional woodworker for 11 years I understand wood movement and its tendencies pretty good. And believe manufactured floor joists keep from squeeking floors better . They don't move. I don't think I have ever found a straight board over 16'. Makes construction more precise to. I use them when I can.
Go check it out. It's a pretty good, easy read. Good luck man !
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WILL1E
Moderator
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# Posted: 5 Feb 2021 02:44pm
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Aklogcabin Did you fill in the web and block in between the I-joist rafters where they cross over the top plate to the outside?
How about blocking between the I-joist anywhere else in the rafters or floor? I've seen some guys cut a piece of I-joist 1.5" narrower than the space between 2 I-joist, then nail scrap 3/4" plywood to either end. That gives them a big nailing flange then. Here's a picture of it.
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WILL1E
Moderator
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# Posted: 5 Feb 2021 02:52pm
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Well, found this bit of info from the manufacturer.
Looks like you can birdmouth the lower bearing wall of an i-joist (Option H1). You can also do the bevel technique that Aklogcabin suggested, option H2.
All kinds of options according to that link.
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Aklogcabin
Member
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# Posted: 6 Feb 2021 11:01am
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On the 16" tall joists I used 2x10s. Ripped one edge on on board so total hight was 16" . Cut to proper length so I had 16" center. Then cut out each corner so it would fit into joists. Doesn't need to be perfect cut . You can put vent plugs in these if you plan open soffit but I like to close them in and use vents n the soffit board.
For floor joists a 2x nailed in , in between the web help direct energy to adjacent joists. Increasing integrity.
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