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Frank, make sure you space the OSB 1/8″ per specs stamped to the face of the product.
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I have been told OSB and plywood are equivalent products. One local supplier went further to state that any perceived differences in function are not "based in reality". Prompted by an irate client, I researched further. Both meet the requirements of the code and hence do not raise problems with the building departments. I called a manufacturer, who said while both meet a given provision of codebooks, plywood is "stronger". Opinions on performance are based upon what may happen when the material gets wet. One lumber yard owner related that when his bathroom flooded, after swelling it returned to its original configuration much more readily than plywood would have. Waterproofing subs seem to prefer to apply their product over plywood. It seems to me however , that once the membrane fails, both ply and OSB will also be ruined (I guess the issue is which will do so more quickly). Others have said that for shear walls, OSB is more stable and will cause less cracking under stucco. It is a more uniform product, not having he voids or delaminations of ply. Also, it is more environmentally favorable, using younger and faster growing trees.
Another observation: make sure the proper side is "up" on the roof. It can be very slick, espcially with sawdust.
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I just finished an addition project. I've been out of this type of work for some time, and always used plywood in the past. The cost difference in OSB vs Plywood prompted me to ask the owner of the lumber yard I was dealing with about it's virtues. He advised the same tips that have been posted here,(proper expansion space, etc.), and then stated he was pleased I was considering OSB. For typical residential construction, he said the only reason he could see for more builders NOT going with OSB was because they were used to plywood, and change was difficult. Well I used the osb. Naturally time will be the ultimate judge, but I must say, it would appear to me that the density is greater in the osb, there certainly did not appear to be any less strength in the roof sheathing. Sooo, I guess until someone demonstrates a real problem with this product, the price seems to attractive to pass by.
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I definitely would not agree with Steve about "OSB stands up to weather better than plywood" at least for roofing concerns. But we use FIR plywood for roofing and floors, just that much more protection against the inevitable rain while exposed during early construction.
MD
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AS A FRAMING CONTRACTOR, I HAVE HAD LESS PROBLEMS WITH OSB THAN WITH PLY . THE OSB HAS NEVER DELAMINATED AS PLY AS OF LATE IS ALWAYS DELAMINATING. JUST MAKE SURE YOU SPACE OSB TO ALLOW FOR EXPANSION, AND ALSO YOU MAY FAIL SHEATING INSPECTION IF NOT SPACED .
*Ed, stop yelling!I agree with you, the OSB I've used has held up very well to rain, while CDX ply sometimes delaminates.
*I just had a customer change all references to OSB in the contract she was about to sign to plywood, which added over $1,000 to the cost of the job. Of course, she forgot to make the change in the payment schedule to reflect that! Anyways, there's always someone out there quick to suggest that plywood is better, but perhaps it's those same people who weren't bright enough to space the edges properly, I've seen several wavy roofs that are blamed on OSB "not being strong enough", when really what's happened is the sheathing has expanded and buckled. I've seen the same thing happen to walls. Years ago, there were lots of problems with floors exposed to the weather, but they seem to be doing a better job of sealing the sheets now. My main objection to OSB is the outgassing, apparently EXTERIOR grade plywood is the best thing to use on the INTERIOR, because the glues are less offensive. However, if you're dealing with a true case of environmental sensitivity and not just paranoia, then you need to examine all the building components, and even exterior plywood isn't acceptable in that case. Concerning thickness, we use a true 1/2" OSB (not 7/16th") on our roofs, with two clips between each rafter, not just one. Floors are 3/4" when over 19.5" or 24" TJI joists, and 5/8" on 16" o.c. unless for ceramic tile floors (3/4" + 1/2" plywood underlay).
*I've got some 7/16" and 5/8" OSB scraps at the job site right now. They have been rained on half a dozen or more times. Not sure I would use the material now but it does not look all that bad and it will hold a nail. Also have some plywood cut offs that that were piled up at the same time. It is warped and delaminated junk. Steve
*I was informed today by the customer who insists on plyood instead of OSB that the pull-out strength of nails in OSB is 15 lbs., while plywood is 30 lbs. Does anyone know anything about the pull-out strengths of each? She also claims OSB has been banned from being used on roofs in many locations, and that it's common knowledge how poorly this product performs. This is all news to me, and I was curious where this information was coming from, her imagination or reality. Anyone know anything about this?
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For general sheathing are there any real differences in OSB/ Plywood? Is OSB ok for floors and roofs? What is industry standard for roofing 5/8 ths or 3/4.
A begginer thanks you
Frank
*When it first came out I had questions about OSB and was reluctant to use it. Over time, I have become a convert. Today's OSB product is superior to plywood for sheathing roofs, walls, and floors. It stands up to the weather better and it is stronger. Some folks think plywood takes and holds nails better but that is not my experience. For roofs, 1/2" is acceptable. However, 5/8" gives you a stronger and better looking roof. Around here, about 1/3 of all roofs are 5/8 and the rest 1/2. Using 5/8 is a premium upgrade. It costs more and is more difficult to handle on top. Price it both ways. I used 5/8" sheets on my keeper house and 1/2" on my cabin.
*Frank - If you do a search on this topic you will find a lot of back and forth on this topic. I am sure that this thread will attract the same. Many people here prefer plywood over OSB.Having said that, I have used 3/4" T&G OSB as subfloor for a while and I prefer it to plywood. I might reconsider if I was doing a project that was going to be exposed to the weather for a while, but usually we don't have that problem.We have put it under carpet, HW floor, and wet bed tile with no problems.As far as roof sheathing goes we have used 7/16" OSB in the past but in the future I am going to try to use 5/8", if I can get it from my vendors. 7/16" is little flimsy, but IMHO most wavy roofs are due to sloppy framing and not so much sagging sheathing.
*Frank, make sure you space the OSB 1/8" per specs stamped to the face of the product.
*In general, OSB is a great product. I don,t like it under hard wood flooring. If I am not framing the house, but installing the hardwood, I request that plywood is installed in the areas where hardwood is installed. Most general contractors don't like this because plywood is more expensive in many markets, and it cuts into the bottom line. I feel the stability of plywood is one of the most important criteria for a great floor. If the whole thing gets carpet and vinyl, use OSB, but as stated SPACE PER MANUFACTURERS SPECS. OSB swells/contracts when temps/ humidity changes more than plywood does, and if OSB gets saturated with water it really expands when the glue breaks down. I would suggest you find out what the most exclusive custom builders in your area use and follow suit.