OSB or Plywood for Truss Gussets?

[MacLawn]

Me? I've read so many of old Eddie's posts here, I'll go with wha' he says. Makes me glad me builder is using OSB for roof sheathing on the additions he's doing on me house. Adding a 12x12 screen room off me wife's office, extending me carport (which I will later frame in to be an enclosed garage) to be 26x32, using OSB for roof sheathing (is that how ye spell that mess?). Also, those glue lam or wha'ever beams to spam 26'. OSB boys, it's OSB. Let's get with ye olde program, it ain't the '60s nary more.

 

[Capricious]

Me? I've read so many of old Eddie's posts here, I'll go with wha' he says. Makes me glad me builder is using OSB for roof sheathing on the additions he's doing on me house. Adding a 12x12 screen room off me wife's office, extending me carport (which I will later frame in to be an enclosed garage) to be 26x32, using OSB for roof sheathing (is that how ye spell that mess?). Also, those glue lam or wha'ever beams to spam 26'. OSB boys, it's OSB. Let's get with ye olde program, it ain't the '60s nary more.

Glad you're happy. And everyone gets to have an opinion.

Mine is that OSB is a step or two below decent quality plywood (CDX is not "decent quality": some true exterior grades are, and the 50+ sheets I have stored in my garage are very good quality).

As for laminated lumber, it's laminated from veneers (as is plywood) and not from chips (as is OSB). At least I've never seen any made from chips.

As for nails not holding in plywood, well, I have never heard of that being an issue. If one is worried about it, there are ringed nails one can use, although the guy who has to peel-up those shingles a decade or two down the road may not be real happy with that.

 

[s219]

Glad you're happy. And everyone gets to have an opinion.

Mine is that OSB is a step or two below decent quality plywood (CDX is not "decent quality": some true exterior grades are, and the 50+ sheets I have stored in my garage are very good quality).

As for laminated lumber, it's laminated from veneers (as is plywood) and not from chips (as is OSB). At least I've never seen any made from chips.

As for nails not holding in plywood, well, I have never heard of that being an issue. If one is worried about it, there are ringed nails one can use, although the guy who has to peel-up those shingles a decade or two down the road may not be real happy with that.

There are OSB types of posts and beams in routine use now, but called PSL (parallel strand lumber) -- see https://www.google.com/search?q=parallel+strand+lumber&tbm=isch. I don't know how they spec; most composite beams I have used were laminated veneers (aka, LVL or "glue-Lam"). And of course don't forget about the i-beam style wood floor joists, that all use OSB for the web.

Frankly, the difficulty of getting good void-free plywood these days really makes it impractical for a lot of projects where it would conceivably be better than OSB.

 

[Capricious]

I think PSL is made of much longer "chips" than ordinary OSB


As for the I-beam joists, I think it has already been pointed out in this thread that the webs are not under that much stress, so one can "get away" with using OSB.

Really good plywood is not hard to get; just really expensive. But I have been building boats with my plywood, and have experimented with exterior grade and a couple
of premium underlayment grades, some of which worked and some of which did not. I started to just spend the money and get the good stuff. I would want the same level of
quality in the structure of my house. One never knows when one might get 6 feet of snow (Buffalo, NY) or maybe a hurricane or two. There are other places to save money
in a house, like on countertops.

By the way, for the lovers of OSB, here is an "OSB" boat, built for a manufacturer of OSB in order to make a point. Please note that this was not built of "off the shelf" OSB.

Yacht for Sale 65' Hugh Saint Custom Motor Yacht | Bradford Marine Yacht Sales


"MISS OSB was built over three years as a no expense spared love affair. When the US and Canadian housing market collapsed the buyer went into bankruptcy and never took full delivery from the builder. This sale is a non core asset of a Canadian corporation in CCAA and the purchase price must be approved by a Canadian court. The original buyer was a manufacturer of oriented strand board most commonly used in the structure of wooden homes and spent over $750,000 in research and development of special engineered woods in oriented strand board form for the construction and decoration of this yacht. The hull itself is a composite of OSB external veneer, layers of structural fiberglass and internal layers of OSB planks...."


EDITED TO ADD: Some more photos, including a few while under construction:

Express Cruiser

Specs show a lot of epoxy resin and various reinforcing cloths (fiberglass, et all) along with a lot of "normal" lumber was used in the construction.

Cost was reportedly about $10,000,000.00 USD.

A lot of money to prove a point, which maybe explains why the original owner went bankrupt.

 

[sld]

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

I don't dispute what you say about the reroofing issues but we had softball size hail a couple of years ago and it went right thru the OSB and into the attic. I don't think there is any way that those missiles would've gone thru 1/2 plywood.

I've noticed on the reroof job that even the OSB blows out on the underside from the nails. It might allow an additional shingle job over plywood but it won't take unlimited nailing. Also, some roofers use more nails than others. Sometimes, way too many.

 

[Bing187]

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

Advantech and zip wall don't do anything to keep wind out. The wind doesn't go through a sheet of anything. It is the seams that let draft through. That's why the seams get taped. The coating on zip wall is a vapor barrier, made so that moisture only travels one way... Out. Absolutely no difference in stopping wind.

Nails hold shingles on the same way that nails hold anything. They separate the fibers of the wood. I don't know why the plywood you've seen has so many voids, but other than the occasional spot, I don't see it in the fir cdx we get here, which is pretty good. Either way, have you ever seen nails come out of the plywood, allowing shingles to fall off? Never. I have stripped and re roofed plenty of roofs done with plywood and have never...... literally never... had an issue with it being unsafe or not a proper roof deck to shingle again. I have, however, worked on houses with osb on the walls, with vinyl over it, where you could pull a piece of vinyl off with your hands, and roofers would come out with it. The remaining nails could be pulled out with my fingers......

My .02 ..... I've been doing things the right way for long enough to have a clear conscience. Building science backs up everything I'm saying. If anyone doubts it, go on Fine Homebuilding, Journal of light construction, or a University that has a building science forum and ask there..... I don't make this stuff up.

I'm out. Good luck.

Mike

 

[s219]

I think PSL is made of much longer "chips" than ordinary OSB

As for the I-beam joists, I think it has already been pointed out in this thread that the webs are not under that much stress, so one can "get away" with using OSB.

Yes, PSL uses thicker pieces of wood rather than the flakes/chips in OSB. They are generally "chunks" of a veneer, similar in thickness that you'd see in plywood. But that's mainly because of the size/scale of the beams made with that approach. There are also thinner OSB beams that generally are sized like 2x lumber.

Nobody seems to understand how I-beams work. Maximum tension and compression are in the flanges, but the web sees the maximum shear, which is very large (commensurate with the tension/compression loads). You can't have those tension/compression loads in the flanges if the web doesn't hold them together. So the web is a critical component and not something you can skimp on.

I think I said it earlier, but anyone who thinks OSB is a cheaper/weaker alternative is about 15-20 years behind the times. It has some compelling advantages over other materials. Also has some weaknesses and limitations, but those are generally well understood by people using engineered wood products and we design around them. Nobody is saying it's the best for everything, but it is better for many applications in construction. An easy example would be using 10' long OSB sheets to go plate to plate over wall framing. The benefit in wall shear strength due to that is something an 8' sheet of any other product cannot compete with.

 

[Hiltz]

Advantech and zip wall don't do anything to keep wind out. The wind doesn't go through a sheet of anything. It is the seams that let draft through. That's why the seams get taped. The coating on zip wall is a vapor barrier, made so that moisture only travels one way... Out. Absolutely no difference in stopping wind.

Nails hold shingles on the same way that nails hold anything. They separate the fibers of the wood. I don't know why the plywood you've seen has so many voids, but other than the occasional spot, I don't see it in the fir cdx we get here, which is pretty good. Either way, have you ever seen nails come out of the plywood, allowing shingles to fall off? Never. I have stripped and re roofed plenty of roofs done with plywood and have never...... literally never... had an issue with it being unsafe or not a proper roof deck to shingle again. I have, however, worked on houses with osb on the walls, with vinyl over it, where you could pull a piece of vinyl off with your hands, and roofers would come out with it. The remaining nails could be pulled out with my fingers......

My .02 ..... I've been doing things the right way for long enough to have a clear conscience. Building science backs up everything I'm saying. If anyone doubts it, go on Fine Homebuilding, Journal of light construction, or a University that has a building science forum and ask there..... I don't make this stuff up.

I'm out. Good luck.

Mike

Im with you Mike. I spent over 40 years in construction building projects signed off by architects and engineers and I never had a issue with plywood. All the high end residential projects specifically called for it.

 

[Bing187]

Im with you Mike. I spent over 40 years in construction building projects signed off by architects and engineers and I never had a issue with plywood. All the high end residential projects specifically called for it.[/QUOT

Can't say I wasn't warned, lol. :laughing:

 

[ace10]

Earlier this year, I modified the trusses on one of the gable roofs over my house.

The engineer was very specific about the material, nailing pattern and glue to be used on the gussets that were scabbed on to the reinforced webs... 1/2" plywood. He stamped the drawing. Good enough for me. :thumbsup: