Hello,
I’m planning to use 1/2″ plywood for sheathing (4000+ sq ft house) and 5/8″ plywood on the roof. I made this choice because I believe (and have been advised) that plywood is generally stronger than OSB. I also believe that plywood will have less of a delamination problem years from now.
The carpenter recently said that plywood is inferior to OSB due to delamination. He told of an example where a not too old house is telegraphing sheathing problems in a wavy roof. I think that most folks use OSB because it’s cheaper and just about as strong, but not because it is superior.
What are the opinions/experiences on Plywood v.s. OSB for sheathing?
Thanks,
Roger <><
Replies
There is a good article in the current issue of FHB regarding ply by vs OSB. Check it out.
Personally, the only problem I've had with 1/2" ply is that I've seen 3-ply delaminate, and that was a few sheets, and that was several years ago...and the ply was from Home Depot (caught short on a weekend). I've never had a problem with a greater than 3-ply sheet.
OSB does have a tendency to swell around the edges when wet, and it may not recover from the swelling when dried. Ply may swell when wet, and if it does, it does recover a bit when dried out.
I have never, ever seen ply telegraph through a roof. I have seen umpteeen cases of OSB telegraphing through a roof.
I wouldn't use generic OSB for a roof or for a subfloor. For subfloors, I'm a 3/4" CDX T&G ply guy, though I may try Advantek someday for floor decking.
I think I'd always use ply for roof sheathing, but again, I may try Advantek someday.
I may try OSB for wall sheathing someday...maybe.
Advantek is an advanced "sort of" OSB. More resin, less prone to water damage, etc.
For you? Sure, use 5/8ths ply on the rof. A fine choice. As to wall sheathing, use what you want, but I'd avoid 3-ply half-inch plywood.
I most certainly agree with Mongo.
If you don't mind the extra $$, go with the plywood. (especially on the roof.)
Lately the difference in cost between plywood and OSB isn't as much as it was before OSB shot up after the Iraq invasion.Use fir plywood if you're worried about delamination.I use OSB on walls, unless it's an uninsulated garage where it won't be drywalled. The plywood looks a million times better.OSB sucks for floors. I won't use it.
"Use fir plywood if you're worried about delamination." The diff is in the glues, noit the wood. Fir is stronger and more resistant to water damage, but it is how well the factory does the glue work that determines whether the sheets will delaminate in the field. Other woods might pucker up more and show it when they delam while the fir plies just sit there wet without moving around so much
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What about that bilt-rite sheathing? I see that alot up here in MInnesota. ALOT
You mean brownboard? I haven't seen it used recently, though it's on our 1976 house.
never hear dof it
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If there's a chance of your subfloors and roof sheathing staying wet for any period of time, spring for Advantek. It costs more, but by the time you figure in replacing a sheet or two for swelling or delaminating, you're ahead of the game.
Scissors cut paper. Rock breaks scissors. Paper wraps rock.
I agree with Mongo.
Take a scrap of OSB and a scrap of ply...... soak both in water for a day or two.... lean both against a wall.... kick down with your foot on each and see which one holds up better.
Cost has always been the only reason that OSB even came into existence.
I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
O.S.B, if it gets wet the joints will swell and that will definitely telegraph. 5/8 shouldn't de laminate. If you used 3/8 I would expect it to. Plywood is your best bet.
after the huricane andrew florida found a lot of osb everywhere except on the roofs check out fine home building jan 93 page 82 to 87. osb failed when it got wet. i think they revised the nailing for osb after that. i am a union journeman carpenter, general contractor, and after 2 heart attacks now teach pre-apprentice 12 week classes for construction trades. I show the huricane article to my students as examples of what an earthquake can do here in calif.
We build in the Pacific Northwest and have used OSB for years. To my knowledge, we have NEVER had a problem with OSB.
We have however, had a problem with plywood delaminating. I'm still waiting to try Advantech, but I'll have to wait longer because it isn't available here yet. Go figure.
We use Advantech on roughly 50% of the subfloors we frame. Other than that, its 5/8 fir on the roof, and 1/2 pine on the walls. You're right.... the delaminating seems to be getting worse and worse with every frame we do. Some times it's so bad that I have to go back and re nail the window openings at about 3" OC just to get the windows tight to the frame if it's been sitting for a couple weeks.
For some reason, OSB seems to equate with cheesy in these parts. At this point I'd try anything other than the plywood. I've probably only framed a dozen houses or so with regular OSB on the walls and subfloor and never experienced a problem. Again, that's only like 12 houses... hardly scientific proof of anything. I've only used it on one roof and I really didn't feel comfortable with that at all, although I know many do it regularly. Unfortunately it is very rare that I get to spec materials.... all I can do is make suggestions.
The 1/2" pine that you use is it 3 ply?It seems like from what I read that a lot of guys frame with hem fir and use pine for sheathing. Every house I've ever built we always use doug fir for framing and we use fir for plywood 4 ply never use pine although I've seen it in Home Depot but never use it. Do you use doug fir when you frame?Joe Carola
Hey Joe,
We don't see much dougfir around here at all. Framing members are mostly SPF, with longer and larger stock (mainly rafter stock over 18') being hemfir. We do get fir 4 ply 5/8 sheathing for some of the better roofs.... that stuff seems to hold up very well.
1/2" pine wall sheathing and 3/4" pine subfloor have been the real problem items with the delamination. Really bad lately it seems, although the weather has been about as bad as it can get..... everything is soaking wet all day and then freezing at night.
I still get lumber drops with 1/2" pine for the roof.... it's unbelievable. Doesn't even meet code, but the yards will still spec it at take off if it isn't already specified on the plans for them. That's how it works around here.... we supply labor and maybe fasteners only.... the lumberyard does the take-off and the GC/builder writes the check. This puts the lumber yards in competition with each other, competitively doing the take-offs..... you know where that goes.
Dieselpig,
We have been using OSB on roofs since I was in high school, and that has been the standard in this area for a long time. Every once in awhile we get a batch of ply from Canada that is so pretty and white, but then the problems started over tariffs and all that jazz.
A guy I play basketball with is a framer and he did a house in the golf course community close by that was all 14' ceilings throughout the whole house. This house was 5000 or 6000 sq and huge. Jasen and I walked through it and the entire exterior was sheathed in ply and many of the interior walls were sheathed with ply (shearwalls) and about half was delaminated. The floor delaminated so bad that when you walked, you would compress the bubble and water would bubble out! It was unreal.
We have never had a problem with OSB on the roof or walls. Of course, we don't let the house sit there in the weather for a long time. If it takes us 2-4 weeks, then at the longest, it's 4 weeks before the walls get housewrap. The roofer shows up the day we get done sheathing the roof usually. In fact, he is roofing while we are sheathing often times. Sooner we can get under a dry roof, the better for us and the house.
Last time I saw CDX in a house,it had bubbles in it too. Advantac is catching on here at around $30 /sheet.
I didn't do it....the buck does NOT stop here.
Since the price/shortage fiasco, around here the ply quality has fallen off.
used to be you could pay a buck or 2 more for fir ply andget good stuff.
I just paid 21$ for 5/8 cdx that was not very impressive.
Mr T
I can't afford to be affordable anymore
to all,
most of the houses I work on are decked in southern yellow pine 1x8's or 1x6's---of course they are 60-80-100 plus years old LOL
I have seen tons of the newer houses( anything less than 60 years old is newer to me) --with delaminating plywood
I have NEVER seen 5 ply half inch cdx----and even 4 ply is at a significant upcharge from 3 ply
We have never had any problems using osb----but then we have the luxury of installing the osb and getting it completely roofed in the same day-----and it's always stiffer than half inch plywood---and flatter.
Osb holds roofing nails ok---but not as good as plywood however
I did do a roof on a neighbors new addition where 5/8 plywood was used on rafters 16 " OC--------damn solid deck.
Stephen
Stephen,
Do you gap the OSB sheets when you put them on roofs or do you butt them tight? Clips?
Do you think the swelling/telegraphing that's somewhat common with wet OSB is from simple wetting and swelling at the edges, or wetting and mushrooming from the sheets being installed too tight to its neighbor and with no expansion gap?
Have you ever done a tearoff over OSB?
Thanks,
Mongo
The telegraphing I see with OSB is sagging between the rafters. It may occasionally be the case that the OSB gets rained on before it's covered, but I never see a roof left uncovered for days around here. But the OSB still sags.
Sunvale Homes ####builder out here(Georgetown, Ontario) uses O.s.b on the roof, and it's nice for walking on b/c of the traction on it. However this guy leaves it out in the weather for weeks.
sounds like this builder is shortening the life of the new houses he builds i often too see new houses that are left exposed even turning grey before the contractor can find time to cover up either plywood or osb the problem seems to be the builder
The thing that bugs me is seeing wood I-beams left out in the weather. I see this a lot in lumber yards, where the stuff is likely left out for months. It comes from the plant with a wrapper, but that's usually gone, or badly torn.
Mongo,
If we are completely replacing decking( a tear-off down to the rafters) we will generally use clips---especially if the situation is trusses on 24" centers.
If on 16 inch centers---not quite as likely to use clips.
If decking OVER something else---like skimming skip sheeting or over 1x8---like in a flat roof situation------we generally wouldn't use clips----but would set spacing with an 8d nail.
I would personally suspect swelling and telegraphing would come primarily from osb getting wet before roofing installed----but I can't prove it.
Yes---I have torn off plenty of roofs decked in osb----but it's not the majority of my experience--------------
when I started out almost all my work came from the older neighborhoods---decking in southern yellow pine 1x8's.----the neighborhood I still prefer to work in is done primarily in syp 1x8----and during the working season I generally will have 3 @ 1x8@ 12 ft. long bungeed on top of my ladder rack at all times.
Later on I started getting into plywood decks from the '60's----tons and tons of delamination problems and virtually every deck from that vintage had 3/8 plywood delaminting at the eaves and all the structural integrity of an old magazine.
I have avoided buying plywood for about 10 years now----since we tore the roof off of a old garage down to the rafters, replaced a few rafters and re-decked the roof in 1/2cdx------the day was getting late and i made the mistake of cleaning up all the debris---instead of felting in the deck. It rained over night and delaminated the plywood in ONE soaking.
the osb-----we are starting to see roofs replaced from the '80's now---so we run into more and more osb( another reason I don't like to stray from my preferred neighborhood)
I can think of one condo developement we have been replacing roofs in for years------we started when the oldest roofs were 17-18 years old( IKO shingles failing) the condos are 3 stories/6 units about 35 squares----the garages are 12 to 20 squares---we have done , I think ,7 residential buildings in that complex and 4 or 5 garages.
most of these roofs were done as complete tear-offs----and we have yet to need to replace a single sheet of osb.
I can't influence new construction practices( if I could--houses would be much smaller---roofs much steeper and they would be slate on solid 1x8. LOL)---------
BUT---I do get to do the post mortem on decisions builders made 20-40-60-80 years ago-----and that influences my preferences.
BTW---tearoffs on osb goes smoothly if nails were used---invariably stapled roofs are a PITA. I don't mind if a roofing nail pulls out comparitively easy on an osb tearoff----as I have never seen a shingle blow off caused by roofing nails pulling loose----every blow off I have seen has been caused by the shingle pulling loose from the nail---not the nail pulling loose from the deck.
Stephen
Excellent, Stephen, just the type of reply I was hoping for.
Thanks much,
Mongo
I'm putting my final lumber list together. Checking and rechecking, finishing touch's, etc.
Here's what I am finding from reading these OSB/CDX/Advantech threads back to 2002! And man it was alot of reading (I didn't read all 500+ LOL).
The majority seems to go with this:
5/8 OSB on my roof decking (apparently roofing failure on this is minimal!).
1/2 OSB for wall sheating.
OSB main negative was its flammability and it requires a closer nailing schedule.
Advantech ia the way to go overall, if I want to spend the extra $$$$. I still know little about this stuff despite its repeated mention. Is it true it $30 a sheet now?
CDX just didn't seem to have many folks overwhelmingly supporting it other than if you get up to the 5/8 multi-ply's. But then its costs was $$$$$$$
I did find MANY, MANY people stating there are different qualities of OSB. Most said DO NOT buy it from the big boxes. But to go with a brand name. But no one ever mentioned a name!?!??!
Funny back in 2002 5/8 OSB was around $5 and Advantech was $8-11
Sound good?
-----------------------------------------------------------------------------
"Have you seen my baseball?"
Ya, in 2002.
A person with no sense of humor about themselves is fullashid
Well thats what I found all the way up until the present. My findings weren't what EVERYONE was agreeing to, just the majority. There were discrepency's of course. The only thing we can all agree on is death.
Thanks for your input -----------------------------------------------------------------------------
"Have you seen my baseball?"
OSB is fine for the walls, I use 1/2" CDX on the roof; my rafters are @16" OC. Trusses are 24" OC that's when I use 5/8" CDX. Advantec is fine for floors (carpet,hardwood, and laminate) I put 1/2" BC or Durock (in the bathroom) on top of the Advantec if I use tiles (cermaic,marble etc....). If you use OSB on the walls make sure that you cover them up (Tyvek, Typar etc.) when you build them!
Mark
Jack of all trades.................Master of none!
Edited 7/11/2005 8:15 pm ET by xxxredsoxxx
Do you walk out on those cantilevered pics?I'm not green anymore.
There cantilever about 5' and yes, I did. The Alum-pole staging was mostly for the window.
(try to make my pics under 100kb I was'nt thinking!)Jack of all trades.................Master of none!
Alumapole has chains to keep the cantilevered walkboard tied down so that shouldn't be a problem if installed correctly.
FF
Alumapole has chains to keep the cantilevered walkboard tied down so that shouldn't be a problem if installed correctly.
Yeah, I know. I've got a bunch of it. The instructions say not to cantilever it out more than a foot. I thought I was living dangerously when I shot it out 2.5' to turn a corner.I'm not green anymore.
Some folks have experienced more sagging of OSB (vs plywood) when used for roof sheathing. This varies, obviously, with the quality of the OSB and the rafter spacing, but it also likely varies with the temperature/humidity conditions where you are -- high temp/humidity is apt to make sagging worse.Especially on a roof, you need to get OSB covered ASAP, before it can get wet.
Dang, I'm on dial up here and now know what it feels like to see a 658KB pic.
It's called cruising on by.be under 100KB
A person with no sense of humor about themselves is fullashid
I thought every one was on broadband......lol :)Jack of all trades.................Master of none!
I agree with Mongo.
Here in the PNW, Doug Fir Plywood is available and is my first choice.
But, having worked for years in the wood products industry, I know from first hand experience that quality varies from mill to mill. I'm dialed in on the good ones and spec their product.
One of the worst things the plywood industry did a few years back was put 4 ply sheathing on the market. Plywood should, IMO, always have an odd number of plys. 1/2" CDX should be 5 ply and you should accept nothing less.
For subfloors, my experience has been that plywood has much better withdrawal resistance than OSB for woodfloor cleat nails and definitely better withdrawal resistance on siding ( You don't always catch the studs).
I built a kit log home for a customer last year, the kit coming from Pennsylvania, and, being used to the wood species here in the West, I came to sympathize with you folks who are building with plantation SYP lumber and plywood.
But just be aware that OSB is a conglomeration of Aspen and Pine and Birch residue....oh, yeah, and some resins (glue). (But if you decide you don't like it, it burns really fast!).
Advantek, which I see such raves about here, is just becoming available, on special order, from my local yard of choice....I might give it a try.
Here, Huber's Advantech is the same price as plywood, but far better than either ply or osb.
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You ever get I joists that have been obviously left in the elements for way to long. We've had some old ones come with new ones , there was almost a quarter inch of size difference.
No, The folks I buy from take care of their stock
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Send them back.
I don't even let them take them off the truck. One times gets the message across.
I think OSB is an inferior product to plywood. When plywood gets soaked in a leak situation it maintains structural intregrity until it rots. Not so with OSB. I havent had problems with ply delaminating with the exception of some bad runs of T-1-11 siding. The larger roofing companies here use a lot of three ply 1/2" for reroofs. From what I've seen its pretty cheap stuff. Doubtful that its grade stamped for sheathing.
Here in earthquake country these houses framed with doug fir and doug fir plywood have held up to the test. My gut feeling is that anything structural made of OSB will not.
Tom
forget about both and use Advantech, especially the 3/4" on subfloors.
Osb is weak and plywood does often delam. Advantec does neither.
Huber makes it.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!