OSB or Plywood

I am working on a new house and am concerned with the wall sheathing/subfloor/roof sheathing right now. Many new houses seem to be totally sheathed in 1/2 inch OSB. I can buy 1/2 inch CDX plywood for $1/sheet more. Is it any better, or is OSB a better product for this. The subfloors will be 3/4 inch plywood so that I can nail 3/4 inch oak floors to it. What about the roof. I often see roofs that sag between the trusses over time. Is 1/2 OSB adequate or should I use 1/2 or 5/8 plywood.
Thanks, Len
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"Leonard Lopez" wrote in message

OSB is cheap, which is why builders use it. OSB is OK as sheathing, but as roof decking it has a tendency to 'telegraph' through shingles in this heat along the Gulf Coast.
I much prefer CDX, in any case. I always spec 1/2" CDX with a radiant barrier and taped joints for sheathing, and 1/2" CDX Tech-Shield for roof decking. For plywood subflooring I generally spec 1 1/8" CDX T&G.
YMMV
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We used OSB for walls (1/2) and floors (3/4), and plywood (1/2) for the roof.
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If they are doing 24" on center trusses for the roof, get them to use plywood clips for whatever material they use.

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Yupper. I just put 7/16 OSB on my roof as part of a build up process. The original deck was 3/4 T/G plywood and we built up over top of that. The OSB spans 2x4's which are 24" on center and I used clips between each 2x4. The result is a deck that is almost as rigid as the original deck. The very slight difference between the two is not worth mentioning. Where I live the snow loads are very heavy. Very heavy. Houses are, and have been for quite some time, constructed with 7/16 OSB on 2 foot spans, with no problems - as long as you use the clips.
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Heard that OSB is actually stronger than the three ply CDX. I don't have the figures to back up that statement but I am sure a web search would yield something for you!
wrote:

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Until it gets wet a few times. Also, think of how each will behave in a fire; all that extra glue in OSB is a substantial additional fuel load. A OSB and truss roof is an unsafe location for a firefighting crew, so we won't go on one if the roof is badly involved. This limits vertical ventilation, which limits fire attack options, which limits how well the fire can be stopped before gutting the house.
For a buck a sheet, you might buy 'em 5 minutes longer on the roof, to make the firefighting that much more effective. Better yet, lose the trusses and use real rafters. Even without considering the World Trade Center, truss construction kills more firefighters than anything else.
Dave Hinz
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http://www.intlbarrier.com/blazeguard.html Looks like some companies are trying to change that. With the available technology, I'd think it would be mandatory to have some sort of retardant either on or in it.

It this because of the flamability of the roof, or the loss of sthrength from being wet?

make
Buck a sheet? That explains a lot. Buck a sheet can add 50 bucks to the cost of a $300,000 house.
If I ever build a new house, the walls won't be wood. I'd use insulating concrete forms (ICFs) and have 6" of concrete and more +R40 performance insulation.
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Speaking as a contractor, do a simple test. Leave a sheet of OSB and a sheet of CDX outside. for a couple of weeks. The decision will be obvious. OSB will turn to mush. Now, onto the roof. You can use 1/2" material but you will see the sags. I ALWAYS use 5/8" cdx on the roof. I ALWAYS use 1/2" cdx on the sidewalls. However, I do use Weyhrhouser brand 7/8" t&g Edgegold (kinda looks like OSB but is a better product) for the subfloor. Make sure to use construction adhesive for the subfloor no matter what product you use and leave an 1/8" gap for shrinkage and swellage (new word). Happy building! SH - From the North Oregon Coastal Region
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