OSB vs. ply roof

[gball]

Ready to sheet the roof on the new garage. Looking for some thoughts on OSB or plywood sheeting. I would really like to use 1/2" ply but at $24 a sheet where i live... I know prices have gone up over the years but I just can't see paying that for a sheet of plywood. I used 7/16" OSB on the walls and it got rained on a swelled instantly. Really i hate the stuff but it comes down to the $. 1/2" osb is $11.77 a sheet here compared to the $24 for 1/2" or i can get 15/32" in 3 or 4 ply from home depot in town for $18 something. The 4 ply is like $.50 more than the 3. I looked at that stuff and it seems pretty crappy too. SO... advice, comments please... we are already getting snow so i need to get moving. might go pick up materials today.

 

[Falcon67]

OSB. If you look at the shiny side, it has a bit of a wax coating that allows it to weather a bit until you get the roof covered. There is no - zero - never - plywood used on roofs around here and they get rained on once in a while. Ply is just to expensive and 1/2" isn't stout enough for a roof IMHO. Mine got wet during the build, no big deal. If it REALLY bugs you, then spend the $125/roll for synthetic underlayment that will not blow off the roof once you tack it down. Comes in 250' rolls - typically - and can be good for up to 180 days of exposure. I used it, good stuff.

Like this:
http://www.gaf.com/Roofing/Residential/Products/Roof_Deck_Protection/TigerPaw

Not sure how you installed your "swelled" OSB, but I used several sheets as a work platform that were out in the weather for several months. They are now used as flooring in the attic. They got a little fuzzy from standing water, but nothing really out of whack.

 

[theoldwizard1]

There is no - zero - never - plywood used on roofs around here and they get rained on once in a while. Ply is just to expensive and 1/2" isn't stout enough for a roof IMHO. .

My son had to have his complete roof re-decked. He was told the same thing. No one uses plywood any more. He paid a couple of bucks extra per sheet to go from 7/16" (standard ?) to 1/2".

I have heard in some areas of the country they use 3/8" OSB which sounds just crazy to me. I think if I had a heavy snow load and a low pitched roof I would go 5/8".

 

[EOC_Jason]

Every roof install I've seen uses OSB...

It never hurts to talk to the people behind the counter at HD. If you are buying a bunch of stuff at once sometimes they can give you a price discount. Also they give military discounts (if you are active / former)...

 

[KenC]

OSB. If you look at the shiny side, it has a bit of a wax coating that allows it to weather a bit until you get the roof covered.

That is true, however, That side should not be up. It goes on the bottom side. If you've ever installed a new roof on OSB you know why. The wax is way to slippery to walk on if the roof is over about a 4/12 pitch. Below that it doesn't really make a difference. But, I wouldn't even attempt a 6/12 with the wax up!

 

[gball]

The OSB i put on the walls got a couple days or rain before i got the wrap on and did swell to i'd guess about a 1/8" over thickness. The board i used on the walls came from Home Depot. I ran out and got 3 sheets from a different "lumber yard". The boards looked, felt, and even cut different. I am kind of doing my own experiment to if there is any difference between them, apart from cost. I was told that the stuff from H.D. and other "box stores" was an inferior product, didn't really believe it. but after seeing this stuff not just swell but chips bubbling off too, i'm curious to see how my test turns out. So, what thickness is the norm of osb on a roof? 1/2" or 5/8". It is a 4/12 pitch and i am in northern Michigan so we do get snow... If i have to use 5/8" it really would be about the same cost as 1/2" ply.

 

[Paul1956]

Several years ago I used plywood on the roof.

First, the plywood was not as slippery as the OSB and thus would
somewhat eliminate my fear of sliding right of the edge.

Second, I was told by the friend who owned the lumber yard that
plywood would hold the roofing nails better.

Fast forward several years... now I see most builders using OSB
on the roofer of new developments. Perhaps my reason #2 is no
longer valid. <shrug>

 

[Scott P]

Why not go with the reflective sheathing for your roof? Is it much more expensive? I sure does help keep the heat out.

 

[#1SomeGuy]

If you can afford it, go plywood (especially if the difference is under $1000)...OSB may be the standard but that's only because it's cheaper. Plywood is just so much nicer to work with, much stronger, more water resistant, etc.

If you can get it locally bluwood sheeting is also a great option but probably even more expensive.

 

[G_P]

If you buy OSB at a big box store look and see how many sheets have the impressions of large bolts/nuts pressed into them! Saw tons at HD that looked like someone tossed a handful of hardware on them and then ran them through rollers.

Found one that actually had a 1/4" nut INSIDE the wood. It wrecked the blade on our panel saw...... Either the machines at the OSB plant are literally falling apart or somewhere along the line people are tossing extra hardware in among the sheets.

 

[Vegaman_Dan]

If you're concerned about the subroof panels getting wet, then you've already failed since the shingles and felting is supposed to be there to keep it from getting wet in the first place. Plywood is also readily damaged by water and can swell.

Put up your choice of subroof, and then cover it with a good quality sheeting protector as mentioned earlier. The you'll have that peace of mind with good water protection.

You'll easily save the money needed for that protection by going with OSB instead of plywood and still have beer money left over for the crew.

 

[jerryd68]

You must not live in snow country, I replaced the roof on my shop this past summer and used 19/32 OSB, it was expensive but the snow load we get in Idaho you have to have it.

 

[pattenp]

Well maybe, maybe not. Read this .... http://bct.eco.umass.edu/publications/by-title/choosing-between-oriented-strandboard-and-plywood/
.. and there have been improvements to OSB since that article was written in 2005.

If you can afford it, go plywood (especially if the difference is under $1000)...OSB may be the standard but that's only because it's cheaper. Plywood is just so much nicer to work with, much stronger, more water resistant, etc.

If you can get it locally bluwood sheeting is also a great option but probably even more expensive.

 

[Falcon67]

Clarification - I did use Techshield OSB on my roof and I do believe the scruffy side was the outside deck. And yes, it's been worth the $2 premium per sheet. I bought mine through McCoy's and the rest of the OSB came from HD. No real issues with any of it.

 

[Tim Kennedy]

gball:
Had an Amish crew raise the walls of my garage 19" last year & that included a whole new roof. I never even considered OSB for sheeting -- went with 5/8" plywood [I agree with Falcon67 - 1/2 is not strong enough for roof] on a 4/12 pitch. Didn't care about the money difference - just wanted it done right. It's solid to walk on. Almost forgot -- if you use plywood don't forget the spacing clips - makes for a much nicer job.

 

[theoldwizard1]

Why not go with the reflective sheathing for your roof? Is it much more expensive? I sure does help keep the heat out.

OP lives in Northern MI. If it gets much above 80F it is a HEAT WAVE !!

 

[mtwaterguy]

gball:
Had an Amish crew raise the walls of my garage 19" last year & that included a whole new roof. I never even considered OSB for sheeting -- went with 5/8" plywood [I agree with Falcon67 - 1/2 is not strong enough for roof] on a 4/12 pitch. Didn't care about the money difference - just wanted it done right. It's solid to walk on. Almost forgot -- if you use plywood don't forget the spacing clips - makes for a much nicer job.

Spending more doesn't make it right. In PDX my neighbor used ply for his shop and I used OSB, everything else was the same. Mine was better. Better support with same thickness, no need to go to 5/8".

 

[7th Kahuna]

Why not go with the reflective sheathing for your roof? Is it much more expensive? I sure does help keep the heat out.

That stuff works surprisingly well (foil side down) but I have only ever seen it on OSB.

If you can afford it, go plywood (especially if the difference is under $1000)...OSB may be the standard but that's only because it's cheaper. Plywood is just so much nicer to work with, much stronger, more water resistant, etc.

I would agree with this. Personally I would prefer the plywood over OSB any day of the week. Cost of course may be an issue.

If you buy OSB at a big box store look and see how many sheets have the impressions of large bolts/nuts pressed into them! Saw tons at HD that looked like someone tossed a handful of hardware on them and then ran them through rollers.

Found one that actually had a 1/4" nut INSIDE the wood. It wrecked the blade on our panel saw...... Either the machines at the OSB plant are literally falling apart or somewhere along the line people are tossing extra hardware in among the sheets.

What is up with that? I have seen it here too.


With OSB, I have seen really inconsistent quality. I was on a job this past spring where just a light morning dew had caused the material to begin to delaminate. I like to see thicker material (5/8ths if possible). We don't have to deal with snow here, but I hate walking around on a spongy roof. Minimum code is just that, minimum. Sometimes it is worth stepping it up a bit. And as for OSB sheeting holding a nail well, never seen it.

That said, if it's what you can afford, OSB is a completely workable solution. I don't know what you are seeing there, but honestly some of the Chinese plywood showing up at the Home Depots here in California isn't much better. Buy from a proper lumber yard if you can.

 

[Vethead]

Plywood all the way, but that is my personal opinion. OSB will work, but I have always found plywood to be stronger, more weather resistant until the roofing goes on, and of a more consistent quality. Had this discussion a bit ago with a builder who was working on the neighbors roof and asked him why he was using OSB vs plywood on that roof. He said because it was cheaper and was still code compliant. Other than that, he used plywood when the customer was willing to pay for the up charge for material. We use 1/2" around here, but we have no real snow loads to worry about, maybe an inch or two a year, sometimes less. I can see how some may feel it is too thin. There are times when I feel a little sag when I would walk on the roof without shingles, but I am a bigger guy.

 

[f150skidoo]

I would never put OSB on a roof of anything. for an example some of the 20 year old subdivisions down in the city came with OSB roof sheathing and on every house you can see a dip between the trusses. Also when i was in high school i would work for local roofer when we redid a roof that had OSB i would always be putting my foot through the roof.

 

[eddie1278]

Plywood for me for everything. I've seen what water does to OSB too many times even the newer stuff. Even if you install shingles correctly they are not bulletproof things happen.

 

[Tim Kennedy]

mtwaterguy:
You used OSB - fine. In my case spending more was right, OSB was cheaper in more ways than money + take it for what it's worth - for the small money difference in 1/2" plywood compared to 5/8" plywood -- when you walk on it you can tell a hell of a difference in stiffness. I agree with f150skidoo -- my neighbor's roof was repaired with OSB & it looks like ****. You want to use OSB, great for you -- just not for me.

 

[NUTTSGT]

I used 1/2" OSB for the garage roof, 24" O.C. with clips. On the house roof, I left the batten boards (from shake roof under the standing seam) down and sheeted it with OSB over that.

 

[lugnut71]

my 2 cents if you use osb on a roof 5/8 is only way to go. contractors around here put 7/16 on roofs , you can see it sag, and feels spongy to walk on.

 

[srmofo]

I've personally fallen through a 1/2 plywood roof. If its a choice between 1/2 ply and 7/16 OSB, I'd take the OSB every time. If youre concerned about nail holding ability , nail a shingle down then pull it up. It'll rip every time. Improper venting and water intrusion will damage the roof deck regardless of its material.

I've noticed lower quality wood anytime there's a large disaster. Quality is **** and it'll cost twice as much

How often are you guys walking on your roofs that it matters if it feels spongy?

 

[ADSR]

OSB is ****! Out west, we are starting to see the building codes getting rid of it. If you've ever built a house, you know the wall bracing doesn't come off until the roof is sheeted. OSB is **** for shear, even if you nail the hell out of it. Everything is being changed for seismic activity.

 

[ADSR]

How often are you guys walking on your roofs that it matters if it feels spongy?

Who cares about walking on it. I don't want it to rip/tear to hell and have trusses flying all over the place in a earthquake!!

 

[mmhouse]

If you can afford it, go plywood (especially if the difference is under $1000)...OSB may be the standard but that's only because it's cheaper. Plywood is just so much nicer to work with, much stronger, more water resistant, etc.

+1

And plywood won't sag or edge swell (which can telegraph through the shingles) like OSB can.

Plywood with ply-clips on the edges is old-school but best IMO.

 

[finn]

Not sure where you are in Michigan, but the inspector here in my area of the UP won't sign off anything less than 5/8" for a roof.

OSB seems to have better dimensional stability than plywood....less wavy.

I haven't seen anyone use plywood for 15 years.

 

[mmhouse]

Here's a very good, and balanced, article on the subject of OSB vs. Plywood....

http://parr.com/weekend-warriors/plywood-vs.-osb-which-is-better/

 

[Average_Joe]

I have seen plywood delaminate in areas from one night of DEW.

I use OSB on walls and roofs, Advantech for subfloors. OSB is also much flatter than plywood.

 

[Average_Joe]

+1

And plywood won't sag or edge swell (which can telegraph through the shingles) like OSB can.

Much better to have to deal with delamination and warping, lol. OSB makes a MUCH flatter roof than plywood.

 

[Punchwood]

If you buy OSB at a big box store look and see how many sheets have the impressions of large bolts/nuts pressed into them! Saw tons at HD that looked like someone tossed a handful of hardware on them and then ran them through rollers.

Found one that actually had a 1/4" nut INSIDE the wood. It wrecked the blade on our panel saw...... Either the machines at the OSB plant are literally falling apart or somewhere along the line people are tossing extra hardware in among the sheets.

THIS !!! I did my garage ceiling in OSB that is FULL of hardware!!!

 

[mmhouse]

I have seen plywood delaminate in areas from one night of DEW.

If it was exterior grade plywood it was defective or of inferior quality (i.e. not APA certified).

I sold building materials for many years and that definitely should not happen.

 

[pattenp]

You need to brush up on your knowledge of OSB. Start by reading this.
http://www.norbord.com/na/blog/plywood-or-osb-panels-which-is-better-2

OSB is ****! Out west, we are starting to see the building codes getting rid of it. If you've ever built a house, you know the wall bracing doesn't come off until the roof is sheeted. OSB is **** for shear, even if you nail the hell out of it. Everything is being changed for seismic activity.

 

[ADSR]

You need to brush up on your knowledge of OSB. Start by reading this.
http://www.norbord.com/na/blog/plywood-or-osb-panels-which-is-better-2

I build homes for a living. The engineers are starting to not accept OSB on the job site. I work with these guys daily. I'm going to go with what they say, over something i can read online.

 

[Average_Joe]

If it was exterior grade plywood it was defective or of inferior quality (i.e. not APA certified).

I sold building materials for many years and that definitely should not happen.

APA exterior plywood, on a commercial building, as spec'ed by the architect. I believe plywood used to be a better product than it is now.

We put in a claim once for delaminated plywood subfloor and after a few months, they agreed to give us some plywood for another layer. Not worth it.

 

[ozyborn]

I would never use OSB on a roof. I use plywood and 3/4 at that. Not from the big box stores but my lumber yard. Just redid my roof a few years ago. all plywood, good rubber membrane and stone coated metal shingles. It will last my lifetime.

 

[ADSR]

I would never use OSB on a roof. I use plywood and 3/4 at that. Not from the big box stores but my lumber yard. Just redid my roof a few years ago. all plywood, good rubber membrane and stone coated metal shingles. It will last my lifetime.

3/4!! That will stop a fall out!

 

[pattenp]

In regards to the strength of OSB. OSB has been shown to be of an equal strength to plywood as a structural panel. This has been stated by the American Plywood Association. So, what is the reason that these engineers are not allowing it?

I build homes for a living. The engineers are starting to not accept OSB on the job site. I work with these guys daily. I'm going to go with what they say, over something i can read online.