UMASS Article: Plywood VS OSB

[Pat Germain]

I'm going to be installing hardwood flooring in my house over the next few weeks. My house has OSB flooring. One of my coworkers insisted hardwood flooring should never be installed over OSB. My research suggests otherwise.

Also, I confirmed the flooring manufacturer warranty states the subfloor must be dry, but does not specify plywood. It seems the actual problems come from particleboard subfloors and not OSB. My coworker insisted OSB and particleboard are the same thing. Of course, they are not.

During my research, I came upon this article about Plywood VS OSB. I think it's very informative and objective. It specifically lists advantages and disadvantes of each product. Surprisingly, one area where OSB may actualy have an advantage is in the ability to hold nails.

http://www.umass.edu/bmatwt/publications/articles/osb_vs_plywood.html

I know many people are against using OSB for just about anything. I think the data suggest it's actually a good product when used properly. Considering the cost of plywood these days, using it may rarely be an option for construction.

The beginning of the article talks about the reluctance of builders to accept plywood when it was new. I think the same thing is happening with OSB.

[Chris Padilla]

Haven't read the article but one reason I chose plywood over OSB for my roof was if the glue fails in either product, at least one has the plys of the plywood to give structural integrity. OSB is nothing but chips if the glue fails.

Okay, read it. They claim delamination of OSD is unheard of...hmmm, okay.

The article is from 2005 but the last paragraph talks of 21 new OSB plant sheduled to open between 1995 and 1997 as if the article was from 1994 or something. Kinda weird.

Well, I went with 1/2" CDX for my roof sheathing, ain't no going back now. :)

[Pat Germain]

Chris, the article does mention that OSB isn't suited for roofing where there's a lot of moisture. I see you're in the SF Bay area. Isn't it pretty damp around there? Lots of fog? Sounds like you made the right decision to go with plywood for your roof.

I noticed the same thing about the dates. I'm wondering if the article was written in the mid 90's, but the copyright is 2006. ??

[Ken Fitzgerald]

Pat,

It's pretty dry here in Lewiston. Our average annual moisture ..12"....2 inches less we'd be a desert. I went with plywood on my shop. I just don't have the faith is OSB yet.

[Matt Ocel]

Ahhhh-

The great Plywood vs OSB debate - One of my favorites.

Why would anybody in the building trades use plywood when OSB is less expensive and out performs, thats right outperforms plywood??

Plywood belongs in the cabinet shop, not on the jobsite.


www.apawood.org (http://www.apawood.org) - Is all I have to say.

Pat,
Use OSB and sleep well at night my friend.

[Greg Cuetara]

I havn't read the article yet but I must say that I had a problem this winter in my garage roof. I have OSB as sheathing and there was an ice dam. Water went up through the OSB like a river running downhill and soaked through it all. Once OSB gets wet it will expand then the problems begin. If I had exterior plywood as roof sheathing it would have gotten wet but the structural integrity would still be intact.
If you have the money use plywood...if not use OSB...there are millions of homes out there which have used OSB. The catch is that most of those homes have not been pushed to the limits so the OSB has been fine.
Greg

[Matt Ocel]

I havn't read the article yet but I must say that I had a problem this winter in my garage roof. I have OSB as sheathing and there was an ice dam. Water went up through the OSB like a river running downhill and soaked through it all. Once OSB gets wet it will expand then the problems begin. If I had exterior plywood as roof sheathing it would have gotten wet but the structural integrity would still be intact.
If you have the money use plywood...if not use OSB...there are millions of homes out there which have used OSB. The catch is that most of those homes have not been pushed to the limits so the OSB has been fine.
Greg


Should have used advan Tek.

[Brian Elfert]

My wall sheathing is plywood and my roof sheathing is OSB. The plywood has less glue so it breathes better on the walls.

[Greg Cuetara]

Should have used advan Tek.

Matt I would have if I had built the house. But sometimes you get what is there and then deal with it.

[Matt Ocel]

Matt I would have if I had built the house. But sometimes you get what is there and then deal with it.


Greg

An Ice dam could be a building defect, how old is your garage? It could be under warranty.

[Jason Roehl]

Well, in the 12+ years I've been hanging out around jobsites, I can say that I have NEVER seen plywood used structurally in this area--it's all OSB. Roofs, walls, floors--all the sheathing has been OSB. Notice, too, (like the article said) that I-joists are made with OSB for the web portion!

[David G Baker]

Jason,
Same here in Michigan. Everything is OSB. It may have to do with our poor economy but there doesn't seem to be any complaints and OSB has been used here for quite a while. We have a lot of vinyl siding on house exteriors and OSB has been the base material of choice.

[Brian Weick]

I would never, and let me repeat that ~ "never" put OSB down for a sub-floor when the plan layout is Hardwood flooring/Ceramic tile , sub-flooring~period. Here is the problem I have with OSB ~ I don't know if you realize this but if for any reason there is an accidental spill of any liquid that OSB could swell up in size and cause major problems with the flooring itself , it also would weaken the bond with the material agents in OSB, and deteriorate. I have seen it, and had to repair it.
I realize the builders are using it because it is less expensive , but that does not make it suitable for every application. I have seen this problem a few times~ and that is exactly what happened when it became in contact with water/moisture. For exterior wall sheathing ~ I have no issue with that application, But I never used that for sub-flooring when a wood flooring/ceramic tile was going to be applied to that area. I just have no faith in OSB for certain applications , and when you think about it and weigh your +/- , you may be saving your self some money now , but you may be paying for it later ,3x more I might add.
I would have to be a nay sayer on this one for sub flooring or roofing. These articles are great information , but I am sorry, there are applications that I would not use OSB. Have you ever seen what water does to this material~ it destroys it, weakens the gluing agent and swells up to almost twice the thickness it was originally, fasteners are no longer doing what they were intended to do and have absolutely no mechanical bond with the material , the result is ~ you have some serious problems ahead of you. In my eyes, it's not worth gambling.
Just my 2 cents:rolleyes:
Brian

[David G Baker]

Brian,
I like plywood for sub-flooring as well and would not use it in a home. I do plan on using 3/4" tung and groove OSB for the floor on the upper story of my small barn where moisture shouldn't be a problem unless I have a roof leak.
I have used particle board underlayment for kitchen vinyl flooring but was also concerned about moisture because I have seen kitchens that had water problems and the particle board turned to mush and swelled to the point that the flooring had to be replaced.

[Brian Weick]

Hey,
in the barn for flooring ~ yea, absolutely, I was just trying to point out that that material is not a good application for the inside of a home or a roof. I have OSB for sheathing on my garage and the roof, It was that way when I bought the house, and from the inside you can see at the eves that it is starting to swell up and stain at the eves ~ going to have to rip it all off and do it the right way. I have seen numerous problems with OSB . if it is a vertical application, I have no problem , or for what you are using it floor ~ absolutely. but not in a home for flooring and roofing.
my 2 cents
Brian

[Steven Hardy]

Interesting article. I would like to read an article dealing with the effect of heat on plywood versus osb. My unscientic observations are that when warmed by the sun,the glue used in OSB softens ,resulting in non-flat roofs.I'm sure it probably softens in plywood also,but natures glue in the natural wood layers has held together for hundreds of years in some cases. I would also like to read an article about formaldihide outgassing in plywood versus OSB....(and what were all those FEMA trailers made with?)

[Chris Padilla]

I guess it probably all comes down to proper installation and proper protection before, during, and after installation. But, then again, this is true with just about everything! :)

[Chris Padilla]

Chris, the article does mention that OSB isn't suited for roofing where there's a lot of moisture. I see you're in the SF Bay area. Isn't it pretty damp around there? Lots of fog? Sounds like you made the right decision to go with plywood for your roof.

I noticed the same thing about the dates. I'm wondering if the article was written in the mid 90's, but the copyright is 2006. ??

Pat,

It is damp in the winter but dry like a desert in the summer so we get both here. RH in the winter probably doesn't exceed 50% very often.

I dunno. My roofer specs OSB and his firm has been around the area a long, long time and he stands behind his work and says he wouldn't use it if it was costing him money 5 or 10 years down the road. I still opted for the plywood...it cost me an extra $400 over OSB for my roof sheathing on a ~15k roof so no biggie in my eyes.

[Chris Damm]

Well let's see, new roof in 2003, had to replace 12 sheets of plywood (due to delamination) on a house built in 1960. Heated garage built in 1983 the OSB was in great shape.

[Bill Cunningham]

I opted for plywood on my shop, because in the past I have seen 'sags' between the rafters of roof sheathed with OSB.. My house was built in the 60's, and has 1 x 12 planks for roofing, the same planking is used below the subfloor of the house..

[Matt Ocel]

I would never, and let me repeat that ~ "never" put OSB down for a sub-floor when the plan layout is Hardwood flooring/Ceramic tile , sub-flooring~period. Here is the problem I have with OSB ~ I don't know if you realize this but if for any reason there is an accidental spill of any liquid that OSB could swell up in size and cause major problems with the flooring itself , it also would weaken the bond with the material agents in OSB, and deteriorate. I have seen it, and had to repair it.
I realize the builders are using it because it is less expensive , but that does not make it suitable for every application. I have seen this problem a few times~ and that is exactly what happened when it became in contact with water/moisture. For exterior wall sheathing ~ I have no issue with that application, But I never used that for sub-flooring when a wood flooring/ceramic tile was going to be applied to that area. I just have no faith in OSB for certain applications , and when you think about it and weigh your +/- , you may be saving your self some money now , but you may be paying for it later ,3x more I might add.
I would have to be a nay sayer on this one for sub flooring or roofing. These articles are great information , but I am sorry, there are applications that I would not use OSB. Have you ever seen what water does to this material~ it destroys it, weakens the gluing agent and swells up to almost twice the thickness it was originally, fasteners are no longer doing what they were intended to do and have absolutely no mechanical bond with the material , the result is ~ you have some serious problems ahead of you. In my eyes, it's not worth gambling.
Just my 2 cents:rolleyes:
Brian


I have built over 500 homes.

OSB swells to almost its thickness? No way dog!

OSB all the way baby!

Once again - plywood in the cabinet shop and osb on the job site.

[Barry Reade]

I'm going to be installing hardwood flooring in my house over the next few weeks. My house has OSB flooring. One of my coworkers insisted hardwood flooring should never be installed over OSB. My research suggests otherwise.
Pat, I am in the process of laying 1800 ft of 3/4X4 red oak flooring and I am putting it over OSB. I researched like you did and found proponents of both. The OSB was already installed in my 15 yr old house and to prep it I used deck screws to eliminate the squeaks, sanded any steps between sheets so it was gradual, and am using felt paper as a moisture barrier (instead of rosin paper). When I did my Florida room it had a deck floor and I had to build it upo so I used plywood instead of OSB. I am using a Bostick pneumatic Flooring stapler that shoot a 15 ga 1/2" crown 2" staple. I am spacing the staples at no more than 8" intervals. So far I have laid about 600 ft in the Florida rm, Master bdrm and closet.
http://greyghost.smugmug.com/photos/298709868_jbW2Z-M.jpg

http://greyghost.smugmug.com/photos/298710106_srtZQ-M.jpg

http://greyghost.smugmug.com/photos/298719294_gLKPX-M.jpg

I am on a very limited budget so I am using utility grade wood and it has a lot of character and the price was right for me ar $.99/ft sq.:D I have noticed that end of the house where I have laid the flooring is much tighter now than it was and the cottin pickin squeaks are gone.:eek:

I also got a Crane jam saw to cut the base boards so I wouldn't have to pull them and reinstall or use quarter molding.

[Jason Roehl]

Hey, Barry, I know what those pieces of blue tape are on the wall for! ;) :D

[Barry Reade]

Hey, Barry, I know what those pieces of blue tape are on the wall for! ;) :D

Jason, You Da Man!!:D;)

[Jason Roehl]

I've left a few of those black marks myself...:eek:

It's that male affliction--"I can do just one more row..." :cool:

[Barry Reade]

I've left a few of those black marks myself...:eek:

It's that male affliction--"I can do just one more row..." :cool:

The blue tape on the wall was for remembering where I was sanding or for where the urethane was being laid. Ya know us senior GOC's don't always remember where we was.:eek:

[Jason Roehl]

Oh, I thought I saw a couple black (mallet) marks next to the blue tape. I do that as a painter from time to time to remind me where I've filled small holes and such so that I can touch them up later.

[Cliff Rohrabacher]

Okay, read it. They claim delamination of OSD is unheard of...hmmm, okay.


I have had OSB delaminate from nothing more than flexural stress.
I rather suspect that they use too little adhesive when making the stuff. The flakes come off with a fingernail flick.