OSB or Plywood for Truss Gussets?

[Capricious]

"...you don't really think that 4x6 1/16th inch plate is carrying any load do you? .."


Yes, I do.

Go here:
http://www.aces.edu/poultryventilation/documents/Nwsltr-73CanYourTrussesBeTrusted.pdf

Look at the first photo.

Yes, that plate was carrying a load.

 

[MH8675309]

Why would anybody try to span 3 feet with either? Seems like a silly question. Even at two feet, I want to make sure the decking is on at least four rafters or trusses. If it was just a small piece two feet long, fastened at the edges, it will fail from it's own weight. When decking a roof, I will cut an 8 foot sheet down to six feet in order to get four feet on the next sheet instead of installing a two foot piece.

Eddie

I know how to frame - did it professionally. The question is a good demonstration of the difference in strength and nothing else.

 

[Bing187]

This place cracks me up sometimes....... I'll put in my two cents tho, against my better judgment.

I've been framing houses for 30 years. 10 working for an old German gentleman, 20 more on my own. I have seen the gradual swing from plywood to OSB. The OSB today is considerably better than 20 years ago. Not my first choice of material, but it is what it is. Advantech is much better than typical OSB. I don't know if it's additional glue, or what, but it doesn't fall apart when it gets wet, and it's warranteed for a zillion years.

OSB has become a necessary evil; There aren't enough good old growth trees to keep turning out good 5 ply fir ply anymore... So we get OSB, and 4 ply plywood. Rule # 1... Fir ply is ok. Not great, but ok. Pine ply is generally junk. Rule # 2.... OSB is "ok", for sheathing walls, IF they can be kept dry. It swells like a bugger at the seams and cut edges when wet, kaka. I don't know if Eddie is referring to Advantech when he talks about OSB being "superior to plywood on roofs" I like 5/8ths tongue and groove Advantech on a roof better than 1/2" ply. Having said, that regular OSB on a roof is garbage... Telegraphs all the trusses or rafters through the roof, sags between trusses, looks awful, and feels like I'm going to fall through it if I step mid span on it...

All of these points though, are moot. As far as gussets go, I would use plywood. I can't explain it through engineering, only through my experiences with both as far as nail holding ability, shear, and tearing apart when stressed. EITHER is probably ok, especially with glue.. I like PL premium... I recall someone in this thread saying not to use Advantech with glue, that it doesn't hold.. I don't know what you're doing wrong, but anytime I've had to pull up a piece of A tech that was glued and nailed with rings, the sheet came apart before the glue gave up.

I'm not crazy about gambrel trusses that depend on a gusset for the joint at the mansard to upper roof juncture. I've done it that way, per plans, but greatly prefer a wall framed so the mansard rafters rest against it, with the upper rafters sitting on top . A good shop built gambrel truss will have a stud in the web that runs down from that junction to the "floor" web, creating a triangle on either side. I don't agree that the gussets only hold the members in place, and don't provide strength... That's like saying that you can balance all the studs in a wall, and sit the top plate on it and not nail any of it since all the nails do is line it all up.. It all works as a system, dependent on all the parts.

If I had to build trusses, I'd use plywood. 2" ring nails, gussets both sides. My preference based on experience......

Mike

 

[Hiltz]

Who makes a better truck, Ford or Chevy ?

 

[mikehaugen]

Who makes a better truck, Ford or Chevy ?

Dodge (ok, Ram I guess) :stirthepot:

 

[Hiltz]

Keep stirring Mike. lol

 

[TomSeller]

Who makes a better truck, Ford or Chevy ?

It depends on what oil you put in the engine. And V6 Eco or push rod V8.

 

[Hiltz]

I guess from the responses it seems to be about half and half. So what I would do is make half the trusses with plywood the other half with OSB. A little test. See which ones last longer. Be sure to post the results, no matter how long it takes, when you have some data. Im kidding of course but see how a simple question on a internet forum can really get people going. Everyone has valid answers.

 

[Bing187]

Keep stirring Mike. lol

Sometimes I just can't help myself. :stirthepot:

 

[EddieWalker]

I don't know if Eddie is referring to Advantech when he talks about OSB being "superior to plywood on roofs" I like 5/8ths tongue and groove Advantech on a roof better than 1/2" ply. Having said, that regular OSB on a roof is garbage... Telegraphs all the trusses or rafters through the roof, sags between trusses, looks awful, and feels like I'm going to fall through it if I step mid span on it...

7/16 OSB compared to 1/2 plywood is so similar for sheer strength that it doesn't matter which one you use on your walls. There might be some tests out there to say which one is stronger, but the reality is that they are both more then strong enough to keep the building standing straight for multiple stories. In standard home construction of one or two stories, it's not going to matter. So for walls, it's a matter of which is more affordable. Advantac or Zip siding is better then both because of the sealant that is applied to the outside of each sheet, and that you can get it in different lengths. But even more important is that advantage of a solid barrier to keep the wind out over house wrap. Wind is the biggest challenge when insulating a home. If you can stop the wind from getting into your walls, you will find that your insulation works a lot better.

The place where it makes a big difference is on the roof of a house using shingles. The secret for a nail to work at holding a shingle in place is that the nail has to go through the decking. The straight shaft of the nail bends the wood as it goes through it and holds it in place. Plywood has so many voids in it that by the time you nail on your shingles, you have dozens and dozens of nails that blow out the plywood and there isn't any wood there anymore to hold the nail in place. OSB is 100 percent solid all the way through, so every nail is solid. The other big difference, and this is even more important is when re roofing a house with plywood compared to OSB. The plywood is pretty much shot after the first roof. Most roofers will still use it, but depending on who you hire, will either cover it real quick with paper to hide the issues, or charge you extra to replace it.

Eddie