Plywood or OSB?

[benchracer]

What's a better material to use for outside garage sheeting, plywood or osb?
What about the roof? Getting ready to build soon.

 

[p_mori7]

I used OSB all around.

If you intend on using T1-11 for siding, you can skip the OSB and nail that directly to the studs.

 

[OldmanB]

OSB is good, until it gets wet, then it expands as it breaks down,if painted or covered you should be ok.Brian

 

[uppster]

OSB is all that is used around here. They have and improved one for floors.

 

[Bigfeet]

As a carpenter I can tell you OSB gets a bad rap. I don't use it much anymore but I've never seen it fail in a situation the plywood wouldn't have failed also. It does swell when it gets wet but so does cdx.

 

[cwlo]

The premium product is Advantech. Its a very dense OSB type product, with a waterproof glue. Great stuff. Comes in thicknesses for floor, roof and wall. The current OSB and plywood leave a lot to be desired. Plywood is not the same as it used to be, and standard OSB is and always was acceptable...no more.


Chris

 

[NUTTSGT]

I'd use OSB for both asit's what I have done before. Currently on my garage I'm putting up some 7/16" OSB that is foil backed instead of using house wrap that I purchased at Menard's about 3 dollars more a sheet on sale.

This is what it looks like, sorry just one sheet up.

 

[Greavous]

Id go with OSB as well. As stated by Bigfeet, OSB has received a bad reputation simply because of its similar appearance to chip board and its worthless cousin particle board. OSB is an engineered product approved by the APA for many applications such as exterior sheathing, roofing and floors. The wood strands are bonded using a thermal set adhesive which is cured under pressure and heat. In my opinion, the only down side is that it cant be finished into something which looks good.

 

[theoldwizard1]

I was told by the guy from the roofing company that OSB is "stronger" and cheaper. As long as it stays dry, you will have no problems.

 

[Will67]

OSB is used for shear wall in CA, not sure if I have ever seen plywood used for shear. Don't know if it is a cost issue or an engineering thing?

My entire garage is sheathed in 7/16" OSB and roof is the radiant stuff. I have hardi-plank lap siding over exterior walls.

 

[KANSASBOY]

http://huberwood.com/main.aspx?pagename=zipsystemwalloverview This is what i used last few times

 

[srmofo]

Everything in my area is put up with OSB. garages and houses. I built my garage with 7/16 walls and roof. I *kinda* wished I had used 1/2 on the roof, but its fine the way it sits with no problems.

It doesnt matter what kind of wood you use, if it gets wet, and stays wet you are going to have problems.

Personally I would focus more on proper attic ventilation and the details of the finish like siding and flashing. An improperly flashed roof line will cause more problems than OSB ever will. And siding that is installed wrong can buckle or even channel water into bad spots.

 

[Mr onetwo]

I used Huber ZIP system OSB.It's the cat's meow.Outside is tight,water-resistant and should last real well.

 

[theoldwizard1]

... I *kinda* wished I had used 1/2 on the roof, but its fine the way it sits with no problems...

I paid extra for 1/2" OSB when my roof decking was replaced. $5-10$ a sheet.

Good thing I was there when the truck pulled up in the AM. It had 7/16" on board. Roofing company actually had to go to another supply source to get 1/2" (actually 15/32").

 

[oldgoat]

For the walls I am OK with OSB, but for the roof I still prefeer the plywood. Now something might have changed in the past several years, but I believe that plywood is better on the roof where it might, well probably, will get wet sometime. Also the guys that I knew back then said that OSB was more inclined to sag and you could feel the difference when walking across it from a plywood roof.

 

[5lima30]

I used OSB for sheathing my garage and then covered it with Tyvek. I then put 1x4 purlins 24" OC and covered over that with rough sawn 1x12 (full 1" thick) run vertical. I think that OSB is fine for not exposed areas. BTW, when I was building my garage 1/2" OSB was abvout $5 a sheet and 1/2" CDX was $8.25 sheet. JMHO.

 

[mmhouse]

OSB is so common because it's less expensive than plywood and almost as good. But if pushed I'd have to say plywood is best just because it stands up better under less than ideal conditions.

In the last home I built I used OSB for wall sheathing but stayed with plywood on the roof because OSB will sag, especially when it is subjected to moist conditions (hot attic air will hold more humidity). I used a composite product for the subfloor - OSB center and plywood outer skins. I had a lot of water on the floor during construction and the composite material stood up well.

 

[NUTTSGT]

I paid extra for 1/2" OSB when my roof decking was replaced. $5-10$ a sheet.

I used 1/2" on the garage roof, 24" O.C. and clips too. 7/16" on the walls.

 

[IDASHO]

Lets make sure we are making realistic comparisons...

If we are talking about say, 7/16 OSB, lets make sure we are talking about 15/32 CDX plywood. Both are structural, both are about 1/2 thick, both meet shear requirements, and both can be used as roof sheeting or wall sheeting. T

Given this, OSB is superior in more ways than one to plywood.

OSB is good, until it gets wet, then it expands as it breaks down,if painted or covered you should be ok.Brian

OSB can be left outside in the weather for months before it absorbs enough moisture to be a problem.

Structural plywood isnt nearly as resistant. Hell, it breaks down just in heat. No moisture needed.

The age and quality of the trees used to make plywood, and the recent changes is chemical make-up of the glues that bond the plys have gone a long way to make CDX plywood JUNK.

 

[6768rogues]

Plywood and OSB have all the same ratings for span and usage in most major building codes. Plywood will absorb water faster but dries faster. OSB has about 50 layers of strands as compared to plywood's 3 to 5 plys, and OSB is more consistent with fewer soft spots. OSB edges swell when exposed to water, but manufacturers have successfully coated the edges with material (blue stuff in our region) to protect those edges. I use OSB because it is cheaper.
For the environmentalists, OSB is considered as a green building material.

 

[srmofo]

Lets make sure we are making realistic comparisons...

If we are talking about say, 7/16 OSB, lets make sure we are talking about 15/32 CDX plywood. Both are structural, both are about 1/2 thick, both meet shear requirements, and both can be used as roof sheeting or wall sheeting. T

Given this, OSB is superior in more ways than one to plywood.



OSB can be left outside in the weather for months before it absorbs enough moisture to be a problem.

Structural plywood isnt nearly as resistant. Hell, it breaks down just in heat. No moisture needed.

The age and quality of the trees used to make plywood, and the recent changes is chemical make-up of the glues that bond the plys have gone a long way to make CDX plywood JUNK.

I can vouch for this, and why I made emphasis on proper venting. When we were putting a roof on my buddies house 2 years ago I stuck my foot through his 1/2 plywood decking. We were stripping it off anyways, but it was still a little unnerving when I busted a hole in his closet ceiling.

A lot of folks also dont realize that you are supposed to reseal any cut edges on OSB. Thats what the blue stuff on the edges is

 

[IDASHO]

Yes, per MFG warranty specs, any time you cut OSB you are to seal the exposed edge.

Even without the sealer though it is incredibly resistant to absorbing moisture.
The glue content is mush higher that plywood and since is is a panel made from small chips, there is no grain to provide a path for the moisture to travel deep into the panel like plywood.

 

[ddawg16]

I had that discussion with my architect......

For shear walls.....OSB is fine....and a lot cheaper....

For roof sheathing....if your rafters are more than 16" OC.....you stand a better chance of minor sagging over time with OSB vs plywood.

On my 2-story addition...OSB on the walls....plywood on the roof and floor.

Side note....a 4x8 sheet of plywood is lighter than the same in OSB....when you are carting those upstais on onto the roof...it makes a difference...

 

[Rust]

So...What is this OSB sealant?
I've been in construction for 25 years and I've never seen it.
Educate me.

 

[mmhouse]

Just FYI, all plywood and OSB is not created equal. Always look for APA stamped panels. Non-APA products may be equal but there's no guarantee and often aren't.

The APA is the Engineered Wood Association (originally American Plywood Association) and sets manufacturing standards for its members. Manufacturers can cut costs by avoiding APA membership and skimping on quality.

 

[IDASHO]

So...What is this OSB sealant?
I've been in construction for 25 years and I've never seen it.
Educate me.

Any kind of exterior paint/sealer

Most builders around here that actually care about doing it right just use Kilz primer/sealer

 

[Daniel Dudley]

I do all my client's roofs with 5/8 plywood. That is just how I roll.

OSB is a lot better product than it was 20 years ago. 15/32 plywood can come in two or three ply. 3 ply is junk, and 4 ply is still pretty fair, although maybe not quite as good as it used to be.

 

[mmhouse]

3 ply is junk, and 4 ply is still pretty fair, although maybe not quite as good as it used to be.

You might find this interesting. I did. My perception has been pretty much the same as yours so this is not what I expected with regard to the design differences between 3, 4 and 5 ply.

http://www.apawood.org/pablog/index...difference-between-fourply-and-fiveply-panels

In my experience much of the non-APA stuff is 3-ply and maybe this has colored my opinion about the quality of the product.

 

[PittsS1]

I used 5/8" ply on roof w/ clips, 1/2" OBS on walls. Got caught in one rain before I could tarp roof with ply on it- edges swelled, delaminated, and waved so much I cut a bunch of it out and put new. It was horrible. Used to be totally Anti-OSB, but have had better luck with it lately than this new crappy ply.

If I had to do again, I'd definitely use Advantech or Zip System... but I think OSB and ply are both fine. If OSB is still inferior like some people say, there will be millions of houses falling apart in a short while as it's all I see used around here

 

[IDASHO]

Like I said, todays CDX ply is JUNK.

To get a sheet of plywood these days with minimal voids AND a good exterior glue, you have to look at an AB Marine, or Baltic Birch.

Both of which far exceed the typical budget for sheeting.

 

[Rust]

This is interesting stuff.
I was in the modular home industry for many years, I was a roofing foreman on a modular set crew, and we cut and nailed miles of OSB and CDX. Up and down the eastern seaboard from Massachusets to N. Carolina, and everywhere in between. And we never treated the cut edges of OSB with anything. Still dont. I could walk to a house being built right now in my neighborhood and would find the cut edges untreated. I find it plausable and understand the concept, but it reads like science fiction to me.


So.. Lets add to this OSB discussion.
I have a relative that bought a half million dollar house and all the floor joists are those engineered joists. 1/2" OSB with dadoed 2x2 purlins (for a lack of a better word).

Heres a link to the product.
http://www.gp.com/build/product.aspx?pid=1390

I think I'd rather lumber. Wouldnt you?
The duct work and utility access, deflection and span range is nice... but c'mon gimmie some freakin lumber for my half mill

 

[mmhouse]

I've never seen anyone seal the edges of OSB that has been cut either and I've been around the building business all my life. The fact is that the worst that's likely to happen if it isn't sealed is that it would swell on the edges and maybe telegraph through shingles or whatever is on top. Not the end of the world and probably not a call-back unless the owner happened to be very knowledgeable and a stickler for detail or it was an exaggerated case.

That doesn't mean that it shouldn't be sealed, just that it typically isn't and isn't going to fail in any meaningful way as a result.

 

[srmofo]

I never said that I sealed mine either, I just made mention that technically you are supposed to do it. I did however make sure that all the cut edges were as far as possible away from the ground, doors, and windows...basically any penetration that might bring water closer to the sheeting.

 

[IDASHO]

. I could walk to a house being built right now in my neighborhood and would find the cut edges untreated. I find it plausable and understand the concept, but it reads like science fiction to me.

Many builders do not treat the edges of cut OSB. It is, however, a requirement of the MFG if you ever have a product failure. The warranty is 100% void if the edges are left raw.

As I have said, OSB is superior in a lot of ways to plywood. But I always cover my bases, and treat my cut edges. Average-Joe-Builder doesnt care a damn about sheeting warranties on a home he will never live in or own.

.
So.. Lets add to this OSB discussion.
I have a relative that bought a half million dollar house and all the floor joists are those engineered joists. 1/2" OSB with dadoed 2x2 purlins (for a lack of a better word).

Heres a link to the product.
http://www.gp.com/build/product.aspx?pid=1390

I think I'd rather lumber. Wouldnt you?
The duct work and utility access, deflection and span range is nice... but c'mon gimmie some freakin lumber for my half mill

You've been out of the business for a LONG time if engineered joists are something new to you. For residential construction they have been the industry standard in the US for more than a decade now.

I honestly cannot think of ONE benefit real lumber has over them.

*Stronger
*Lighter
*Straighter
*will never twist
and CHEAPER

 

[mmhouse]

...
You've been out of the business for a LONG time if engineered joists are something new to you. For residential construction they have been the industry standard in the US for more than a decade now.

I honestly cannot think of ONE benefit real lumber has over them.

*Stronger
*Lighter
*Straighter
*will never twist
and CHEAPER

I can think of one. Since lumber is not an 'engineered' product floors built with it are typically stiffer because they are 'over-built.' When floors are built with engineered joists to minimum or close-to-minimum standards, which they often are, they get a little bouncy (too much deflection). Of course this can be remedied by up-sizing but that costs more so is often not done. Yes, lumber can be over-spanned also but that seems to be less common in the typical home.

 

[IDASHO]

Doesnt matter.

Lumber has load ratings just like engineered stuff. And if you think an engineered joist floor is more prone to being bouncy, then you are wrong.

 

[mmhouse]

Doesnt matter.

Lumber has load ratings just like engineered stuff. And if you think an engineered joist floor is more prone to being bouncy, then you are wrong.

Well, there I go then!

Seriously, you're right. There are span tables for lumber just like EWP. But lumber is a natural product with lots of variation - most framing lumber is visually, not machine, graded - so allowed spans need to assume the worst. EWP can be taken much closer to the limit because it doesn't have the variation.

 

[mmhouse]

Doesnt matter.

Lumber has load ratings just like engineered stuff. And if you think an engineered joist floor is more prone to being bouncy, then you are wrong.

Well, there I go then!

Seriously, you're right. There are span tables for lumber just like EWP. But lumber is a natural product with lots of variation - most framing lumber is visually, not machine, graded - so allowed spans need to assume the worst. EWP, because it's a manufactured product, is much more consistent so can be taken much closer to the limit.

So yes, I think you're much more likely to get the design deflection with EWP than with visually graded lumber.

 

[IDASHO]

So yes, I think you're much more likely to get the design deflection with EWP than with visually graded lumber.

So you honestly think todays lumber is worth a ****?


Todays SELECT is worse than #3's were 10 years ago.

Its junk.

 

[mudhog]

Everybody comments that all the houses are built with OSB. That's the way it was in my neighborhood also. I didn't want osb because of a shed I built using it pretty much had to be replaced because of swelling ang sagging. I paid $600 extra to have similar sized plywood put on my roof instead of OSB. My house and the neighbors house was built in 1994 we had a hail storm that was hugh the size of baseballs about 4 years ago. his roof had holes busted through it. I could not find any damage to my roof, I hired a inspector and he looked and found no structure damage but told me the shingles need to be replaced because the hail damanged the shingles. My neighbors house had to have the deck replaced and he went with plywood this time. I am not a expert and I have no studys or charts to show you and I do not know what rating these products have I'm just stating the facts on what happened in my neighborhood.