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Small Cabin Forum / Cabin Construction / Laminating Girders
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# Posted: 26 Jul 2020 21:02

A few years ago i started planning for a remote cabin, and that was put on hold because of it's back on And i have a tonne of questions. I'll create various post to keep each subject separate for the forum's sake

My first questions, is about creating my girders.

My girders will probably be 3 plies of 2x10, maybe i'll make them 4 plies just for stability and overkill

They will be 28' long and will sit on top of 5 cement block/piers (2'x2'), and spaced by 4.5' (considering each pier is 2' wide) (28'-(5*2')=18'/4=4.5)

From reading many posts on this forum, sometimes people mention "laminating" support beams, ridge beam, girders. I've also seen some comments from OwenChristensen about laminating them in a way so they don't warp or twist. But i haven't seen any details of how to do that.

So i'm wondering if

1. is there a special/best way to place the 2x to prevent warping & twisting
2. is there a better nailing pattern to use?
3. what nail type/length is best
4. i'm assuming i should use construction adhesive between each layers of 2x...or should I not?
4. and of course, always try to offset splices by at least 4 feet, and make the splices so they sit just above my pads, this too is just to confirm and to let everyone know, i know

any other guidelines to make the best structural beam possible?

Without a good foundation, it's just a waste of effort!

# Posted: 26 Jul 2020 22:56

Skip the adhesive. Base the strength of the girder on the size of the 2x and number of laminations.

16D hot dipped galvanized nails are best, electro galv nail gun nails okay unless the wood used is PT. You only need enough nails to hold the girder laminations in place. They don't add to the load carrying. Two near top edge and bottom edge every couple feet is good.start nailing one 2x to the next. Clinch over the protruding points. Then add and nail each additional layer. I like 4 layer 2x girders for stability.

Start with as straight as you can get, build the girders quick as you can and then get the floor assembly done as soon as possible. That will help keep things straight.

Building the girder in place on the piers is better than trying to lift an assembled beam onto the piers.

As you said, splices over piers for full support and stagger the splices.

# Posted: 27 Jul 2020 07:21

Structural screws or through bolting will be better than nails. With 2x10s you dont need so many piers. Granted 28ft dosnt lend to putting any normal length lumber over a post very well.

If you have any frost I wouldn't just put pads on the ground.

# Posted: 27 Jul 2020 09:31

I would use adhesive. Have you considered a versalam ? Probably spelled wrong. A 2” wide laminated beam that can be ordered that length. Haven’t checked price in a while but maybe cheaper then a stack of two bys. They stay straight and are stable. I also believe that because they remain stable by not moving such as happens with moisture changes. Floors tend to squeak less.
I started using them along with the laminated floor joists and 16” wide x 30’ long joists to span the 24’ length of my garage with a shed type roof. With the floor joists I could handle them by myself a lot easier also.
I don’t know how the lumber looks at your local lumber store but the wood we see can be pretty crooked. Or I spend an inordinate amount of time picking through lumber. They when I go to use it it seems like a different stack.
Just a suggestion if you haven’t checked out that route. Good luck.

# Posted: 27 Jul 2020 19:03

thanks all for the good advice.

The girder will be made of PT lumber, as my pads will not be too high...just high enough to make the height of the pads + the height of the girder = 18+ inches. So i got enough ground clearance to prevent for rot and allow air flow under the cabin

For the question about pads...i think it'll be easier for me to do pads because my location is pretty hard to access. I'm still not sure how i'm going to be bringing 16' lumber i'll need for the floor joists. But that's another problem on it's own. No way to bring any kind of heavy equipment to dig the holes. I'd have to dig all the holes by hand. There is frost here, but i think with the right grading and management of rain water, i should be fine. Lots of camps in the area built on skids or cement blocks with little to no maintenance.

For the laminated engineered lumber, they usually come in the exact length you if i don't know how to bring 16' lumber to the camp, i'm almost 100% sure it'll be impossible to bring a single piece of wood that's 28' long I think it's way easier to just build it on the spot with shorter lumber. Plus i like the fact that the birder is wider by laminating 4 pieces of 2x. It's much more stable

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