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WILL1E
Moderator
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# Posted: 8 Jul 2021 08:39am
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So for our 16x30 T&G log cabin, i will have 3 built up beams that are constructed of 3 layers of treated 2x8's. I have some questions:
-Do i need to use adhesive between the plys?
-Splices need to fall over the piers, but i should never have more than 2 of the 3 plys do that right?
-Code says to use "10d at 32" o.c. at top and bottom and staggered and two at ends and at each splice". I get the top/bottom every 32in and at ends and splices, but i'm confused about the "staggered" part. Anyone have an illustration?
-I've always assumed screws are better than nails for holding power. However, the code doesn't give an alternative screws to be used for anything but drywall. Does that mean i can't/shouldn't? I have a framing nailer so i don't mind nailing, just want it to be strong.
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ICC
Member
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# Posted: 8 Jul 2021 09:29am
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No adhesive. The adhesive is used for sub flooring to prevent squeaks. For built up beams adhesive is not recognized as adding any strength and just costs more.
With three layers there should only be one splice in one layer over one post to be ideal, but two layers with splices over the same post is okay as long as they are not in layers that are immediately adjacent to each other. As few splices as possible makes a beam that would be able to carry a higher vertically applied load, but the posts under each splice is what supplies the load bearing strength.
Staggered. We have three layers. Let's call them left, center and right. Staggered means that nails into the left side should not be aligned with nails from the right side. Stagger the right side nal a few inches along the length from the left nail. The nails are mainly there tio hold all the layers in alignment, sandwiched over the posts, not to provide any load bearing load transfer from one layer to another.
Most screws are weaker in shear strength than nails. That applies especially to those gold zinc plated screws many of us love so much. They are heat treated to make them resist screw head tear out. That makes them brittle. Some screws are structurally rated. Those have a tested shear strength. Screws do resist pull out better but that depends on the resistance the wood provides. If the wood splits, no pull out strength. When excessive shear loads are applied to nails the nail deforms. They will not ftacture. A screw can be handy to draw two pieces together but in most cases is not an approved fastener.
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WILL1E
Moderator
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# Posted: 8 Jul 2021 10:24am
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Quoting: ICC With three layers there should only be one splice in one layer over one post to be ideal, but two layers with splices over the same post is okay as long as they are not in layers that are immediately adjacent to each other. As few splices as possible makes a beam that would be able to carry a higher vertically applied load, but the posts under each splice is what supplies the load bearing strength.
Got it. I was trying to avoid boards over 16' for easier transport and reduced cost per ft. Using 16' would result in 2 splices on 2 of the piers. If i go up to 22' boards, i can get the splices down to only being 1 on 3 of the piers. FYI, my piers will be 8x8x16 blocks stacked 2 wide and 1-2 layers high on top of a precast 24x6 concrete pad.
Quoting: ICC Staggered means that nails into the left side should not be aligned with nails from the right side.
Now that makes sense. I thought they were trying to imply staggering along the length of a single ply, that's where i was getting confused. So is it safe to say that the center ply will only have the ends of the nails in it and the heads of the nails will only be on the exterior sides of the left and right plys?
Thanks for the wisdom ICC
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Brettny
Member
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# Posted: 8 Jul 2021 12:13pm
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Why not skip the plywood and use 2x10 or 2x12?
Also they make ring shank nails you can shoot through a gun and il be damned if I have ever been able to remove one. Last time I tried I was trying to take 7/16 OSB off held on my ring shank nails..ended up having to rip the OSB off the nail heads.
Also if your useing PT you need hot dipped galvanized nails. Any nail, hardware or screws that goes through PT should be hot dipped or rated for PT. Stainless is also good.
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ICC
Member
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# Posted: 8 Jul 2021 01:16pm
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I think he was using the word "ply" as in 3 layers of 2x
Good point... PT needs stainless or hot dipped galvy nails. I don't recall ever finding anything but electroplated galvies in collated gun nails. Those do not have a thick enough coating of zinc, unless something has changed.
As for nail length we would use true 3-1/2". The nails for the first two layers would be clenched over, then the other layer(s) applied from the other side.
Spiral or ring shank are great for holding power. Also note that the suggested nail pattern is using common nails. The actual shank size (diameter) is listed as well as length and the 10D, or whatever size. Many nailgun nails are not true to the common nail specs. They are more like box nails (thinner) and sometimes 1/4" or so shorter. A 10D common is 3" x 0.148". I see a part box of Paslode gun nails on the shelf in the shop that are 0.120" and some Hitachi that are 0.131". So, I would add an extra nail for every 3 or 4 common that were called for. It is possible to find true common size gun nails. We used to buy Senco true to common size.
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Brettny
Member
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# Posted: 8 Jul 2021 02:44pm
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I know Bostitch does sell PT rated nails that fit there nail guns that are also ring shank.
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WILL1E
Moderator
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# Posted: 8 Jul 2021 03:18pm
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Quoting: ICC Many nailgun nails are not true to the common nail specs. They are more like box nails (thinner) and sometimes 1/4" or so shorter. A 10D common is 3" x 0.148". I see a part box of Paslode gun nails on the shelf in the shop that are 0.120" and some Hitachi that are 0.131".
Why the heck would they do that?!?!
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Brettny
Member
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# Posted: 8 Jul 2021 03:38pm
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$$$
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Nate R
Member
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# Posted: 9 Jul 2021 08:05am
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ICC...not that hard to find PT rated gun nails.........
https://www.homedepot.com/p/Paslode-2-3-8-in-x-0-113-Gauge-30-Degree-Galvanized-Ring- Shank-Paper-Tape-Framing-Nails-2-000-per-Box-650383/100351707?MERCH=REC-_-pipsem-_-10 0351706-_-100351707-_-N
These are hot dipped galvys...
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