OSB vs Plywood

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Uncle Buck
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OSB vs Plywood

Post by Uncle Buck » Thu Sep 07, 2017 1:36 pm

Seems OSB is becoming more common in subflooring and roof sheathing than plywood.

The internet has plenty of debate but would welcome opinions here on which is better.

OSB would save me $1200 on my project but I do not want to cut corners if plywood is still the better choice.

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A. Spruce
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Re: OSB vs Plywood

Post by A. Spruce » Thu Sep 07, 2017 2:00 pm

Personally, I prefer plywood because it does not swell, nor does it lose all structural integrity when it gets wet, unlike OSB which is glued wood fragments, that expands like a sponge and loses all structural integrity when it gets wet. Why is this an important distinction? Because OSB has a tendency to sag between rafters when used as a roof deck, and roof leaks can go unchecked for months and years before being detected. Toilet seals go bad and you may not realize it until the toilet or you fall through the floor. Far more damage will occur with the use of OSB over plywood.

The ONLY advantage that OSB has over plywood is price, and I've done enough repairs involving OSB failures to say that repairs will cost you far more than the initial cost of material difference.
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Re: OSB vs Plywood

Post by DanM » Thu Sep 07, 2017 2:06 pm

I would say it depends on what you're doing.

For sub-floor I really like the good 3/4" OSB we use at work all the time. Basically I would break sub-floor boards down into 3 categories: Cheap OSB, Good OSB, Plywood. The good OSB is imho the best overall, and it's a little less expensive than plywood. The stuff we use (framing new homes) has a 180 day no-sand guarantee and it actually lives up to that. It gets rained on all the time before the roof goes on and doesn't expand, or warp like cheap OSB does, and it doesn't 'bubble' or de-laminate in heavy rain like plywood does. If your sub-floor is going to be exposed to the elements for awhile I would recommend it, if it isn't then pick either good OSB or plywood. Plywood will be better in the long term but it is slightly more expensive.

For roof sheathing 1/2" plywood is better than 7/16" OSB in every way except cost. Plywood feels a hell of a lot more sturdy when you're walking around on the roof working, and it won't degrade anywhere near as quickly over the long term. 7/16" OSB rots out/falls apart really quickly if water starts getting trapped underneath your shingles for whatever reason. That being said, OSB is fine and usually won't run into problems as long as you replace your shingles before they go to complete s**t and make sure all the flashing is done properly. IMHO if it's your forever house go with plywood, if you're gonna sell it in a few years go with OSB and save a few bucks.

For wall sheathing I'd go with 7/16" OSB. Walls tend to not have to deal with water anywhere near as much as the roof does so just save yourself a few bucks and go with OSB.

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Re: OSB vs Plywood

Post by Shannon » Thu Sep 07, 2017 8:24 pm

I understand Spuces points but I have to agree with Dan here. Good OSB has its place. You need a fair bit of water infiltration to rot 1/2" OSB and plywood would eventually fail as well if you have that much of an issue with moisture.
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