why use OSB instead of plywood?

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Old 09-11-08, 11:14 AM
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why use OSB instead of plywood?

whats the difference guys? for a wall(sheathing) or a roof? what is the advantage of OSB?
thank you
 
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Old 09-11-08, 11:49 AM
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In my opinion, OSB is about 1/2 the cost and also has lines on the rough side to line up w/ your studs or rafters, either 16" or 24" OC. On roof sheathing, the rough surface gives better traction. Keep in mind that OSB have directional strength and need to be installs w/ the 8' direction, perpendicular to the rafters.

My 2 pennies.

Jim
 
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Old 09-11-08, 06:54 PM
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is OSB better than plywood? why? can it be used anywhere plywood would be used; sheathing,substrate,roof ect...?
 
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Old 09-11-08, 06:57 PM
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Your concern is quality re: roof installation for plywood vs. OSB. While many install OSB, plywood is preferred. Reason: OSB tends to swell when exposed to moisture. Plywood is more dimensionally stable.

http://www.pathnet.org/sp.asp?id=17336
 
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Old 09-11-08, 08:32 PM
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where is OSB preferred then? also,can i have an example?
thanks
 
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Old 09-11-08, 09:14 PM
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Like Jim said, OSB is preferred because of COST, and that's it. The lines are a bonus.

If your OSB never gets wet because of a leak or anything, it will be fine no matter where it is used. But if the OSB gets wet and stays wet, it will rot faster than plywood because it is more absorbent.

In theory, roof sheathing and wall sheathing should not get wet if everything is done properly, so it shouldn't be an issue. But you have a few people who absolutely refuse to use OSB because it's inferior to plywood, and the only reason to use it is cost.

So let's say you're having a house built. You can use OSB for the floor or plywood for the floor. Since the house will get rained on a lot before the roof is put on, many people opt to use plywood for the floor because it won't swell as bad. But on the walls, some people figure that once the OSB is covered with Tyvek it will be fine. Or once the roof is covered with felt paper, it will be fine.

I have no strong opinion one way or the other, but I don't think anyone will argue the fact that plywood is superior to OSB in many ways.
 
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Old 09-12-08, 05:39 AM
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so is OSB basically particle board?
 
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Old 09-12-08, 05:58 AM
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Not exactly. Partical board is basically saw dust and glue. OSB is wood chips and glue.
That's an over simplication but you get the idea.
 
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Old 09-12-08, 06:50 AM
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Mark is right. Many people confuse OSB with particle board when really the two are nothing alike. Some people refer to OSB as "wafer board". OSB stands for oriented strand board. Chips of glue coated wood strands, or wafers, are laid in a particular direction and pattern and then they are pressed together to give you the most strength from the lamination of multiple layers. 1/2" plywood may have 3 or 4 layers, while the strands in OSB are so thin it has many times more layers. APA ratings printed on the boards give you a true comparison of the qualities of each.
 
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Old 09-12-08, 07:39 AM
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Until 7-8 years ago OSB was not code compliant for roof sheathing in my area. I think local building offices finally caved because of the cost savings when plywood costs soared.

I use it for wall sheathing, but I would not use OSB for roof sheathing because of the reasons Xsleeper mentioned. Plywood will withstand an occasional wetting without damage.

This topic has been discussed here many times.
 
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Old 09-12-08, 08:48 AM
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so those that used particle board now use OSB>?is OSB as cheap as particle board?
is partcle board ever used for roofs? or does it have the same issues as OSB?
 
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Old 09-12-08, 10:17 AM
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Particle board looks like fine bits of sawdust that have been glued and pressed into a sheet. It looks nothing like OSB, which looks like a patchwork quilt made of larger, irregular shaped chips of wood. Unless you are patching a small hole in a roof and it's the only thing you happen to have lying around, you would never want to use it on a roof, IMO. Anything that is not APA rated EXPOSURE 1 should not be used as roof or wall sheathing, because it will not hold up if it gets wet. Particle board turns to punk when it gets wet.

To my knowledge, particle board has never been used as wall or roof sheathing. Back in the late 60's and early 70's it was used in some areas as a subfloor. Usually those people who used it were sorry.

Nowadays types of particle board are used as a substrate for countertops that will be covered with laminate, and low grade cabinets have certain parts made particle board. Sometimes you will see shelving made from particle board, either with or without veneer.
 
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Old 09-12-08, 11:42 AM
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if we have old 1 x 8's under our old siding and want to replace damaged pices to install new siding over it,do we still have to use 1 x 8 or can we just use plywood? will it be thicker than than the 1 x 8?
how do we know if our old siding is aspestos? what does it look like? how does it look different than wood?
thanks
 
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Old 09-12-08, 04:35 PM
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Both plywood and osb come in various thickness. If your 1x8 is actually 3/4" thick - use 3/4" osb/ply. If it is a full 1" thick you could use 2 layers of 1/2"

The only asbestos siding I'm familiar with are stiff brittle shingles nailed up for siding. They paint well if prepped right. Wood can be scraped down to raw wood, asbestos is basically the same through out.
 
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Old 09-14-08, 03:26 PM
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I'm not sure what the big deal is. OSB uses waterproof resin glue. I had a 1'x1' piece of 1/2" osb laying out all winter long the other year as a test and it just faded. One edge was factory painted and the other 3 were cuts. I am not sure what everyones problem is with the newer OSB.
 
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Old 09-15-08, 07:02 AM
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don't know about anywhere else, but in Volusia County, Florida......Daytona Beach, etc.....,

OSB can not be used for roofing according to newer code....swelling, separation after a long time where moisture is present.....

Still can use it on wall sheathing but code requires tyvek on top of it.....Inspector tells me its possible that in Florida, OSB might eventually be banned for exterior walls completely.

For roof sheathing on trusses at 24" o.c., minimum requirement is 15/32 CDX....

There is a new product called ZIP Roof which is a compressed OSB with a coating on top that has passed code. Minimum is 1/2" thick. It had a problem where if any roof was greater than 4/12, it was probably too slick for roofers to be safe on but I understand from the manufacturer that an additive is now used that makes it not so slippery. The advantage to builders is time.....no underlayment required......the seams are taped and the shingles go right over the top.....Passed code here last year. They also make a wall sheathing product, but don't know the code issues with it.....Used the roofing product myself and am happy with it.
 
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Old 01-02-13, 03:19 AM
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Cool An Anecdote

When I was a bit younger, I bought a home in Moreno Valley, California. The area had seen explosive growth, with endless tracts of quickly-built ranch-style homes supplanting the previously endless groves of citrus trees. (Makes me wonder what they did with all of the trees?)

As has been stated elsewhere in this thread, OSB is often used to save money. That was most assuredly the case here: the green lumber they used to frame the houses resulted in studs that were about as straight as a dog's hind leg. At any rate, there was a particular house that caught my eye and I decided that I wanted to buy it. As luck would have it, another fellow had literally slept on the sidewalk in front of the sales office in order to guarantee that he--and only he--would make a bid on that house.

It was on a corner lot, had two storeys, four bedrooms, and two and one-half bathrooms. I wound up buying a one-storey, three-bed/two-bath house across the street. I spent a year and a half admiring that house that I'd wished I'd bought, until one day I learned why one doesn't use OSB for rooves or for floors.

The man who'd slept on the sidewalk had a niece. This young lady came to visit for a week. As is the case with many teenagers, she had a penchant for taking baths and showers that used 'way too much water and took 'way too long. This resulted in the upstairs bathroom's floor getting quite drenched. That was perhaps a month before the decisive event.

My neighbor, who pretty much never used this particular bathroom, had to do so because the shower in his own bathroom (the one adjoining the Master Bedroom) had a clogged drain. The following morning, as I was leaving for work, I saw an ambulance in his driveway. He was on a stretcher, with a blood-soaked sheet covering him. I asked the paramedics what had happened but they just asked me to stand clear.

Once they had driven away, as some contractors began taking charge of the situation, I walked to the open door of the house and looked in. What I saw told the tale all too eloquently.

A dining table in the center of the room was broken, and a chandelier lay broken atop it. Above them, a splinter-fringed hole, with rivulets of water dripping from its edges, gaped from the ceiling. Apparently, my portly neighbor had emerged from his shower--stark naked, as most of us are at such a time--and stepped out onto the bathroom floor. As he did so, it failed to hold his weight and--much as Tom Hanks did in the movie, "The Money Pit"--he fell through it. Only my hapless neighbor did not have a carpet to break his fall. No, he landed on top of his dining set with the chandelier between his legs and, predictably, broke it into pieces.

Apparently, the OSB had been used as upstairs subflooring and no moisture barrier was placed between it and the sheet-vinyl flooring that was installed on top of it. During her week-long visit the previous month, his niece had so saturated the OSB that it became unstable. When my corpulent neighbor (some estimates had his weight at between 300 and 350 pounds) stepped out of the shower, he fell through the floor.

What I've always wondered is: why didn't he fall through it while stepping into the shower? If he had, at least he would have been dressed when the paramedics carted him away. Being taken like that, with all of the neighbors standing around and gawking, must have been quite embarrassing for him. As we never spoke of it, I guess I'll never know.

I moved out of the neighborhood soon after that. Closure of March AFB caused many local jobs to evaporate, mine among them. At any rate, by the time I left, I was no longer envious of my neighbor for the great deal he'd gotten on that house on the corner lot.
 

Last edited by the_tow_guy; 01-02-13 at 06:28 AM.
 

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