Hey Guys,
Sean Groom and I just wanted to stir up the waters a bit by asking your thoughts on OSB vs. Plywood. We’re planning a comparison article for an upcoming issue and would like some thoughts.
Ply/OSB are considered by some to be the same, others swear by one and hate the next, and some like plywood for certain jobs/areas of the project, and OSB for other jobs/areas of the project. So let’s get this thing going, which do you prefer and why? Keep in mind that we don’t necessarily want you to take this opportunity to stubbornly declare that you like one over the other, “just because†J
-Justin Fink
Replies
If ya wanna stir up the waters, you sure picked a good topic. (-:
I like plywood and OSB in different circumstances for different reasons.
For floors, I like plywood better. I think it lays flatter and gives you a smoother floor surface to work with. (Haven't tried Advantech yet, though)
For roofs, I thing the OSB is a bit better. I like the fact that it lays flat when you put it down.
Same for wall sheathing. OSB lays flatter, and is less expensive. No reason to spend the extra money on plywood.
If you don't get lost, there's a chance you may never be found.
Well Boss, let me ask you this....if you like to use OSB on the roof, do you leave the 1/8-1/4" gap between boards to prevent ghost lines from swelling?
p.s. - advantach is a genuinely great product, Mike Guertin cut a piece and soaked it in a bucket for a recent review we did and it didn't swell a bit.
<i"...do you leave the 1/8-1/4" gap between boards to prevent ghost lines from swelling?"
Never seen that done before.
And I've never seen "ghost lines", either.If something is so complicated that you can't explain it in 10 seconds, then it's probably not worth knowing anyway.
Ok, I might have made up the term ghost lines, I'm not sure though...
but I'm sure you have heard of what I'm talking about - some roofs have OSB that swells at the edges and pushes the pieces together making a bulge - and if the bulge is bad enough you can see it through the shingles. This is especially true on hot summer days with poorly ventilated attics. ...I'll look into the Ghost Lines thing to see if I made that up.
"The term ghost lines or roof ridging was coined to describe the effect of osb edge swelling under thin roof shingles" -Paul Fisette http://www.umass.edu/bmatwt/publications/articles/osb_vs_plywood.html
....Knew I wasn't crazy
I knew what you were talking about, though I hadn't heard that term before--we called it "telegraphing" when we saw them on a roof we'd done earlier. We were working on another house across the street from the first house and when we'd take breaks to warm up around the fire (I know, we were wimps) at about 10 a.m., the sun would hit that roof just right and you could see the joints in the OSB. We never left spaces, even though some sheathing (plywood I think) actually is sized a little short to allow for 1/16th inch gaps between pieces.
BTW, I'm not saying this means you aren't crazy. Just in this particular instance maybe not. ;-)
Edited 8/17/2004 8:43 pm ET by Danno
The last time a big hurricane hit south Florida (before this one), I think it may have been Andrew, they showed film footage taken from the air above some housing tracts. Entire neighborhoods had all the shingles blown off the roofs, but nothing else. Other neighborhoods had the shingles and the roof sheathing completely gone. You could see the stuff in their houses throught the open roofs. What was the difference? The ones that only lost shingles had plywood sheathing. The sheathing that flew away was OSB. All the nails were still in the tops of the rafters (or trusses), but the nail heads had tore through the OSB. This could be a good argument for using staples, but for me it was a good argument for not using OSB. I don't use it on anything, anytime. Everytime I see a sheet I think about all those houses with the roofs gone.
are you aware that there were a couple of in-depth studies done after that and they found that the reasons for the roof failures you describe were from failure by builders to adequately nail down the sheets by using enough nails as required by codes ( which the inspectors also failed to inspect and ensure) or by driving the nails too deep.
What you saw of osb vs ply may have been incidental rather than causal.
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I live and work in the southwest corner of Idaho. we are a very moderate climate, with low humidity. Its a great place to live and work, because of the mild climate. But anyway, I haven't even seen plywood on a job for sheathing or subfloors in five years. Generally speaking, that is. Its all osb. One contractor I frame and side for uses 5/8 osb on roofs occasionally. Usually its 1/2. I see the infamous ghost lines on roofs occasionally, but usually because cheap shingles were applied. I'm not a big osb fan and will look for Advantech when I start my own new home in the very near future. I build my floors the old-fashioned way, with 2x8's on 16" centers and pony walls every 8 ft. I can get away with 3/4 subfloor sheathing and not bounce. I framed in central Florida in the mid-70's, stick framing roofs and decking with 1/2" plywood. I liked the plywood for roofs at the time. I just finished a 3600 sq.ft. house for my main contractor and the last time he visited me, his comment was, "Just remember, every time you saw into a 4x8 sheet of that stuff, (osb) you cost me $20.00." This from a guy who never worries about cost as long as the result is excellent.
I suspect that a lot of the plywood/OSB debate may have to do with weather. In drier climates OSB probably performs well, but in humid climates it can sag when used for roof sheathing. And probably in Seattle-like climates OSB is a problem because it's harder to get it covered before it deteriorates, whether used on roofs, walls, or floors.
No doubt there are composite products that perform better in humid or wet conditions.
I wasn't aware of those studies. I just remember seeing the film footage and making the mental note not to use OSB. As some others have mentioned, the technology has probably advanced to the point I should probably rethink that decision. Thanks for the input.
The interesting thing about the results of those studies is that they concluded that the failures were not because of inadequate codes, but poor installations and inspections.
So instead of fixing the problems, they added more stringent code requirements and stricter licensing policies when using the inspectoirs to educate and inspect the work being performed would take care of things. After this recent hurricane hit the west side of Fla, someone remarked, "yeah, we'll see a whole bunch of new regs again now" intead of enforcing the old ones.
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Concerning staples--of course you can't use staples anymore in Florida, and I think everywhere else too (?--don't know for sure). We used to put shingles on with staples. Did a roof on a small lake on Friday and a storm came up over the weekend. On Monday we went back and replaced about a quarter of the shingles.
They found in Florida during the huricane (Andrew) that the sheathing would get wet and swell and that along with the movement caused by the wind, would make the staples cut right through and soon the sheet is peeling off and flying to the next county. Don't know if that happened more with OSB than plywood (or vice versa).
I don't doubt that ghost lines exist - I've just never seen 'em.Better to remain silent and be thought a fool than to speak out and remove all doubt. [Abraham Lincoln]
I also agree with Rich - I would prefer to use plywood whenever possible, even with the cost differential. Stiffer, can handle a freak rainstorm (with the right glue), screws and nails seem to hold better. If you buy 5 ply, it even seems to lay pretty flat for sheathing walls and roofs.
The only thing I can think of to recommend OSB is it apparently has a lower environmental impact vs. plywood, but I wonder if the fewer trees is offset by the additional glue + nasty vapors in OSB.
I don't really like OSB, if you didn't get that from the gist of my message...
Wylie
Success = Work+ Risk + Luck, in that order. Muriel Seibert
I prefer OSB usually except for the critical floor which should be Advantech. I remember the first time I installed OSB 3/4 T&G subfloor. I was shocked that one man could do it by himself. With plywood you had to master the sledgehammer in one hand-one foot on 2x4-other foot 4' away holding the tounge down-dance. OSB lays flat so you just engage the groove and nail it down. Other problems like delaminating plies in a fresh load from the yard are not an issue with OSB.
OSB is almost always cheaper, so you would expect those doing substandard work to use. I think this explains some of the mentioned problems in this thread. Production framers might miss most of the fasteners on a panel edge which causes it to lift up and telegraph through the shingles. This may explain the "ghosting".
Jon Blakemore
osb ? never used a single piece...
lot's of plywood..... but for the past three or 4 years, all of our subfloors have been Advantech...
now.. wind design speeds of 110 mph for our area we have a choice of blocking all edges within a 4' perimeter ( including the ridge if you have a vent slot )... OR...
we can use 5/8 T&G with no blocking... guess we'll be using Advantech there, too..
so will we use osb ?.. why ? not unless a huge price differential comes into play...Mike Smith Rhode Island : Design / Build / Repair / Restore
JFINK: Mike Guertin is a wimp!!! I left some outside in a puddle as a walk board that lasted for over three years, and it did not noticeably change dimensions. No edge swelling; no delamination; no furry ends raised up. Still had a smooth surface on it. Used it for something & had to saw it - just as hard to saw as new.
That stuff is better than night baseball - which my wife, a Braves fan, is watching as I write.
DonThe GlassMasterworks - If it scratches, I etch it!
"For floors, I like plywood better. I think it lays flatter and gives you a smoother floor surface to work with."
I had barely read this halfway through when I already anticipatred you, thinking, Boss has never used advantec, I'll bet. I let out a belly laugh when I read the next line, "(Haven't tried Advantech yet, though"
I notice that you like plywod because it layus flatter and you like OSB because it lays flatter.
care to clear that up for me?
I stayed away from most osb for what seems like decades after seeing the disasters wrought by the old Waferboard predecessor of OSB. Then when they came out with Oriented Strand Board, I held onto my prejudices and occasionally had them confirmed by flaking edges and swelling that I saw on various jobsites. The only place I would accept it was for wall sheathing.
But a couple of three years ago I saw Advantec in action on another job here - winter framing where it gets wet and stays frozen or wet for a long time - disaster for plywood in most cases. On my next job I got Advantec and never looked back. I rarely get plywood anymore, except for certain underlayment or trim/soffit jobs, but I still won't buy OSB. I frame my roofs from sticks @16" OC but if I had trusses or any other framing @ 24" oc, I would be using 5/8" plywood
As a shingle layer, I would prefer plywood when it is good five ply, because it is far easier to hand drive nails into compared to the hardness of OSB
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"I notice that you like plywod because it layus flatter and you like OSB because it lays flatter.
care to clear that up for me?
Guess I didn't explain that too well, huh?
The roof plywood we get around here typically has a big bow in it. So it's hard to get it to lay flat on a roof. You have to stand in the middle of it, or start nailing from one edge and work towards the other.
The 3/4" T&G ply doesn't seem to have that problem. It seems to lay fairly flat right out of the pile. And I like the fact that the SURFACE of the plywood is smoother than OSB.
Does that explain it any better?Happiness, n.: An agreeable sensation arising from contemplating the misery of another.
Yes it does, but the surface of the Advantec 3/4" T&G is smoother yet.
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I don't doubt it - I just haven't seen a sheet of the stuff yet.Life is what happens to you when you're making other plans. [John Lennon]
When I can get ply with more than 3 plys (half-inch ) thats my choice, osb has its place too tho' I use it frequently for sheds and secondary uses. Any thing temporary. But again, with ply prices way up,osb is getting more use by me.
Eitherway, the stuff (both CDX and OSB) with the damn STRINGS in the core is a major PITA.
I have seen the string core (fiberglass,or polyester) in 1/4'' luaun, and I frequently cut that with just a knife..the strings can make a day turn unhappy fast.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Piffin,
The point you bring up about the shoddiness of waferboard and past strand boards is a good one. I think lots of builders tend to group OSB in a category with waferboard and the like thinking that they are all the same type of low quality. The important thing to remember is that OSB is technologically manufactured so that there are about 50 thin layers of wood strands and each layer is oriented at a 90 degree angle compared to the one above and below. In other words, the layout of plywood was a winner, but OSB was supposed to be an improvement on plywood while still using the same type of methods. But the bottom line about OSB that people need to realize is that it is not just waferboard - and it has come a long way. Of course, plywood is nice too...so I try to stay neutral :)
Don't know the formula, but Advantech appears to be a type of OSB. How would it be classified.
http://www.huberwood.com <--- that's the maker of advantech
Yeah, thanks - I already knew who makes it. My question is "Is Advantech included in the OSB column". Huber calls it a "strand product". My experience with it is that it's far superior in most catagories to other OSB products. I prefer advantech for most applications over plywood. I prefer plywood over OSB for most applications if advantech is not available.
I'd think it would be important to emphasize those differences and the technical manufacturing aspects in your article, maybe with a tour of a manufacturing plant.
I am no fan of LP products, having once lived right next door to one of their plants. ( Lot's of other reasons to hate them that I won't go into here) This was in about '82 or thereabouts when OSB was taking the market over from waferboard and LP was making the osb.
But folks in the area could buy a whoile bunk of "seconds" straight from the plant for $15 when the retail was about $4.50/sheet. You had to take the whole banded bunk and there was always plenty of them awaiting. Sometimes they would be culled because of size or out of square, but more often because of inferior lamination. They had to keep the heat, pressure, and amount of resin/glue all just right to produce a good sheet and with that many variables, it took quite awhile to get things running smoothly.
All that to say, that even tho OSB has improved in some ways, the plant it comes from can make a big difference in the performance, just like with plywood.
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You wonder where all those seconds went! How many roofs that blew off, etc. were sheathed with it. Yipes. Between that and the new PT wood that dissolved the fasteners, makes me want to hide under something sturdy--but what can I rely on? Guess I'll just dig a hole and close it up after me! ;-)
LOL, I know where some of those seconds went.
Most that I know of went into storage sheds, garages, and that sort of thing, where inspection was not an issue.
I worked for one contractor who built an addition for his Ex-wife and her new hubby as part of their divorce settlement. He had us put the seconds on that for wall and roof sheathing, but was decent enough to have us double ply it and glue it up for insurance.
The sheets that were culled for being off size or off square, were a pain to use, but were generally sound as any other osdb of the time period. It was easy to tell if the bunk was culled for delam problems - it would be obvious.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
>> ... one contractor who built an addition for his Ex-wife and her new hubby ...
Fascinating. An S&M relationship with three M's. All three of them must have been going around wearing a sign that said, "Kick me harder."
Edited 8/18/2004 10:34 pm ET by Uncle Dunc
Let's try to stay on topic here -
LOL
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
What's so wrong with using boards? After reading all of these replies I'll never touch OSB or Plywood again. Not really but it's a helluva bad idea.
I've often wondered if for roof sheathing (at least up north) it wouldn't be better to cut the plywood into about 16" wide strips (presumably with T&G joints or clips or something to eliminate the need for blocking).
When a sheet-sheathed roof heats and cools, especially in extreme conditions as when there's bright sun on one side and snow on the other, the rafters expand and cause gaps at the sheet joints. This stresses and eventually splits the shingles.
If the sheathing were in narrower strips the expansion would be spread across more joints, so less stress on the shingles.
A bigger issue for me is the quality control (or lack thereof) of both products.
Plywood with huge vacant spaces are becoming more and more prevalent. OSB that falls apart just by looking at it cross-eyed... big problem.
Putting the quality issues aside, I prefer to use plywood whenever I can. Plywood provides "less bounce for the buck" for underlayment. Plywood is less likely to have screws or nails tear through the product under stress. Plywood doesn't bow near as bad on a roof after years and years of weather.
Biggest selling point for OSB is the cost. Especially with plywood prices skyrocketing. I still upgrade the OSB at least one thickness if substituting for plywood (when possible).... so the cost factor is minimized.
I also admit to some "old-fashioned" thoughts about OSB. I just can't get past the thought of glue and wood chips being as strong as wood... even if it is plywood that is held together by glue!
Of course, all of this is just my humble opinion :)
This is a surprise (probably to both of us), but I agree with everything Rich from Columbus said. In addition, plywood is stiffer than OSB and plywood edges seem to swell less than OSB's. Power nails will often blow through OSB, seldom happens with plywood. On floors, where the house goes through a Michigan winter, the OSB begins to flake apart (I didn't work on many houses with plywood underlayment, so maybe plywood just delaminates)--OSB doesn't take kindly to snow, snow shovels, mud, water, etc. .
Advantec for floors, Osb for walls and roof. I switched to Osb several years ago because CDX I was getting was crap. Tried three different lumber yards before I switched. Plywood is stronger I believe, but not enough to make a large difference.
mike
You might want to check with some of the building departments out here in earthquake country. Shearwalling is an important thing for them. The LADBS Type V sheet says Struct #1 Plywood for that, no mention of OSB being acceptable.
-- J.S.
While my preference is plywood most locales I work in in SoCal accept OSB Struct I for shear purposes.
Bing
We're in Seismic zone D1 (high seismicity) and we allow the use of OSB...the shear capacity is there but it must be nailed (or stapled) correctly.
I've been sheathing with plywood, and using aliphatic resin glue in addition to nailing 8d's at 4" on the edges and 8" in the field. My theory is that glue spreads the connection over a lot more square inches, so the load in pounds per square inch goes way down. That, I guess, should help a lot with a relatively weak and non-uniform material like OSB (or not-so-good plywood).
In all the pictures I've seen of collapses, explosion, earthquake and storm damage, it seems to be mostly that wood comes disconnected from wood. Wood breaking happens a lot less often, and when it does, you usually don't also have connections that have survived.
-- J.S.
Hi john,
It sounds like you're doing things right. I have a couple comments though. Your nailing pattern is adequate for a medium level of shear. Lightly loaded shear walls can be nailed at 6" o.c. around the perimeter and 12" o.c. in the field. As the shear loads go up, the perimeter nailing requirements reduce to 4", 3" and 2" o.c. If nailing is required to be 2" o.c., a 3" nominal member (stud) is required at all panel edges. If you are in seismic zone D, E or F (which we are here) and your shears exceed 350 plf, 3" nominal boundary members are also required...including sill plates. The plywood/OSB and it's nailing requirements are totally dependant on the structure. You could get by with 6" o.c. for a tool shed but that probably won't work for a 4 story condo.
As far as gluing, the code prohibits using glued shear panels. The panels may be glues however, the nailing alone is all that can be considered to resist shear forces. The reasoning behind this is that if the glue were to fail in a seismic or wind event, the failure would be sudden and catastrophic...like a brittle failure. Buildings need to absorb and disipate these forces without members fracturing
The requirement here is 6" edges and 12" field, so I decided to go 4 & 8 as added insurance. Any tighter than 4" edges, with nails coming at it from two pieces of sheathing, gets to be an awful lot of steel for a piece of two by to absorb. I hadn't heard of the brittle failure reasoning for glue. Along with more than adequate nailing, it's belt and suspenders I hope.
-- J.S.
Yeah, that is a lot of nails for a 2x to absorb...this is the reason that the code wants to see a 3x member when nail spacing needs to be tightened.
The glue issue is for high seismic areas. It can be used as suspenders but the nails must be installed to meet the full capacity of the anticipated load.
We build in the Pacific Northwest and we use OSB for everything, but overhangs. We have only had to sand OSB floors when we first used it 15 years ago.
I have noticed that the new LP Orange Edge (I capitalized it and don't know what the proper name is :-( ) performs much better here in the winter. We used the old grey edged LP OSB and then on the next house used the orange edge. This was back in January and the orange edge looked much better after all the rain we had. Neither floor has been a problem. We've had good success with Weyhauser Edge Gold also.
We try to gap the OSB on floors and roofs and aren't too picky about it on walls. We have NEVER had a problem with edge swelling. What I have noticed is that perfectly driven nails (shear) can look slightly overdriven after the walls get wet. Solution? We put the house wrap on now while the wall is flat on the deck, unless it is raining.
Problems we've had with plywood:
1) delamination within a week or so. This has happened more often than it should.
2) In doesn't want to lie flat on the roof or walls. I'm speaking of 1/2" ply here. The pile that comes banded from the lumberyard (even if it's 40 sheets) has a curve to it. We try and stack it in such a way that we don't contribute to the problem.
I will probably always choose OSB over ply. My understanding is that OSB is a stiffer panel that Ply, but both hold nails roughly the same (This was in an older JLC article).
I am still waiting for Advantech to make it up here. Last I talked to them (Builder's Show in Vegas in January), they were building a plant that would suppy this area. Sometime soon, we'll start having shear inspections on our roofs and we'll have to use t&g or block panel edges, and I have heard good things about Advantech for all applications.
That's all I can think of right now. I hope that helps :-)
Edited 8/17/2004 9:01 pm ET by TIMUHLER
I do mostly renovations and see products after 10 or 20 years. I have found that OSB goes soft and flakes if any amount of moister has been present over time. It should never be used in bathroom areas at any time.
George
Traini,
You should also keep in mind though that you are looking at OSB that's 10-20 years old as far as technological advances go. There is no doubt that OSB used to have a bit of a faulty reputation, but advances in the industry seem to be bringing it back in a big way...and as a matter of fact, OSB has passed ply as far as sales go nationally.
You might also want to look at what's going on with the makers of plywood and OSB, for instance:
http://www.matr.net/article-6403.html
-- J.S.
Seems odd that they would be closing down now, when plywood and OSB prices have been at record levels.
Even though prices have eased a bit, they're still awfully high.In our civilization, and under our republican form of government, intelligence is so highly honored that it is rewarded by exemption from the cares of office.
Did you notice that article is from a year and a half ago, before the recent surge in prices and building?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Yup. Supply goes down, then prices go up. Adam Smith had it right.
-- J.S.
In my area it is common to use both on a new home. Advantech, an OSB T&G subflooring product, 3/4" is used on the floor joists. 7/16" OSB is often used for side wall sheathing. 5/8" plywood is used for roof sheathing. The products are chosen for price as well as performance. Due to the increased price for sheetgoods, some owner built homes are using board sheathing. Adhesive is used on the floor material but is not as common on walls and roofs.
The Advantech makes a very sturdy floor and has a fifty year warranty. Under tile or vinyl a backer is added. This can be a plywood or cementitious product specifically for the purpose. Carpet & padding or wood products are laid directly on the surface.
There are too many replies for me to read. But, if I were an author planning on writing with some authority, besides getting feedback from contractors I'd speak to independent experts and industry experts. They will have done actual designed experiments and can discuss the pros and cons of each material. The US Forest Products Lab is one that comes to mind.
The lumberyard mistakenly dropped off a sheet of OSB on a delivery and I was in a pinch and needed spacers for headers so I used what I could then left about a quarter of a sheet outside in the elements along with a scrap piece of plywood. Here in the midwest we have had a lot of rain and after two months of being exposed to the elements the plywood is just as sturdy as the day I left it and the OSB is crumbling apart. But I have seen some plywood that comes from discount building suppliers look pretty bad. So, from my perspective, unless I'm building a house in a large warehouse so as to not expose it to the weather, I'd stick with plywood.
Yep, that's been my experience. Especially as a DIYer who can't always work real fast and take advantage of the good weather (that only seems to occur between 8-5 on weekdays), OSB is to be avoided in anything that might be exposed to the weather for any period of time during construction.
I always, until a few years ago, used plywood 3/4 t&g for sub-floor, 4ply 1/2 for roofs BUT after a roof properly done (gaps and all, the company rep inspected it) buckled to hell and back I quit using it.
3/4 of the roof buckled after the homeowners were in. big time. I called the company (Georgia Pacific I believe) and they flew an engineer up at my expense. He looked at the roof, said nothing, flew back and in his report wrote that although the ply was put on properly it buckled because the house was built on a lake ......they refused to replace. My local supplier (just cause they knew me) agreed to replace the ply, if I paid for the labor. My insurance said that because it wasn't actually my fault they wouldn't pay.
With murder/malice in my heart I had to tear off, tarp, replace, reshingle the roof..........and deal with the by now unhappy homeowner.
Todays plywood sucks.........so does OSB.