OSB vs Plywood for Roof
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cjoffutt
Silver Member
Built my house 9ish years ago and used 5/8" OSB on top of Room in Attic trusses spaced 24" on center for both house and garage for me. 9 feet of Ice & Water shield followed up by Permafelt. Then used Decra metal shingles. About as leak proof as one can get. Not a single sag/wave in the roof decking.
Did use plywood for the floor decking as I found a killer deal on craiglist for some some 'extras' from an apartment complex that was being built. Wasn't really sure if it was extras or 'fell off the back of the semi'. But for $4 bucks a sheet for 3/4" tongue and groove, I didn't care, put the 4 skids on the gooseneck and got the heck out of there.
Did use plywood for the floor decking as I found a killer deal on craiglist for some some 'extras' from an apartment complex that was being built. Wasn't really sure if it was extras or 'fell off the back of the semi'. But for $4 bucks a sheet for 3/4" tongue and groove, I didn't care, put the 4 skids on the gooseneck and got the heck out of there.
fried1765
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For a real building, the lumber yard gave you good advice!
For a "woodshed" OSB will do.
fried1765
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mike48130
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There is a difference between types of OSB. My local lumber yard, not big box, sell OSB and builder grade OSB for cheaper. I asked what the difference was, and they told me it's the type of glue they use in the OSB. The cheaper stuff is not so good with water so if it's going to be sitting out in rain before shingling, something to think about.
I would think 24" with 1/2" OSB is ok. I've seen them use 7/16" with 16"OC.
My biggest pet peeve is with truss roofs, most contractors don't take the time to install them properly and the peak ridge is not a straight line. They use the walls to align the trusses, and the ridge becomes a wavy line. If you drive around and look at houses, you can see the waviness in the roof even once it is shingled.
I would think 24" with 1/2" OSB is ok. I've seen them use 7/16" with 16"OC.
My biggest pet peeve is with truss roofs, most contractors don't take the time to install them properly and the peak ridge is not a straight line. They use the walls to align the trusses, and the ridge becomes a wavy line. If you drive around and look at houses, you can see the waviness in the roof even once it is shingled.
EddieWalker
Epic Contributor
ZIP is better then both by a huge margin.
When comparing brand new half inch construction grade, three layer plywood to OSB, there will be no performance differences between the two, which is why OSB meets Code. OSB varies in price during the year, from less then $7 to twice that much. Half inch plywood is going to be $15 to $18 pretty much year round. 1/2 inch ZIP is going to be $20 a sheet plus another $28 for a roll of ZIP Tape. I would have to double check, but I think the green half inch ZIP System goes on 16 inch centers and the Red 5/8's ZIP System goes on 24 inch centers. I don't know what the 5/8's costs. With ZIP System on the roof, you don't need roofing paper.
ZIP is a very high grade of OSB. It cuts clean and you never find any voids in it. You can also buy ZIP Panels longer then 8 feet. I've bought 4x9 and 4x12 for walls that I wanted to avoid a small piece or to run it from sill plate to top plates, and from sill plate to the peak of my ridge. This increases the strength of your wall sheathing tremendously!!!
OSB and Plywood require clips if you have 24 inch centers for your rafters or trusses.
Both brand new OSB and Plywood will hold the nails in place just fine. The nail has to go all the way through the OSB or Plywood. The point does not hold the nail in place. The shaft is what holds the nail in place and it needs to be longer then the thickness of the shingle and the OSB or Plywood. 1 1/2 inch nails are the smallest that should ever be used on a roof. Crooked roofing companies will try to use shorter nails to save money, but just like using staples, this leads to failure.
The biggest difference between plywood and OSB is that during nailing, plywood will blow off that bottom layer of material. This is very common and something that I see when I'm up in an attic all the time. I've never seen it so bad that it's the cause of failure, but it is dramatic enough that I will never use Plywood for roof decking. When that bottom layer is gone, you will often see that there is a huge void there too, so the nail is only being held in place by one layer of material, or a third of half an inch. What is the math on that? For me, OSB is far superior to Plywood on this issue.
Something that I see too often in houses, is people having half inch sheetrock on their ceilings with 24 inch centers. This leads to sagging and even cracking in the ceiling over time. 5/8's sheetrock has to be used for 24 inch centers. With a fairly smooth texture on the ceiling and paint with a little bit of reflection, this becomes obvious. This is also why flat paint and thick texture, like popcorn, was so popular for so long. It hides the imperfections that come from using half inch sheetrock on ceilings.
When comparing brand new half inch construction grade, three layer plywood to OSB, there will be no performance differences between the two, which is why OSB meets Code. OSB varies in price during the year, from less then $7 to twice that much. Half inch plywood is going to be $15 to $18 pretty much year round. 1/2 inch ZIP is going to be $20 a sheet plus another $28 for a roll of ZIP Tape. I would have to double check, but I think the green half inch ZIP System goes on 16 inch centers and the Red 5/8's ZIP System goes on 24 inch centers. I don't know what the 5/8's costs. With ZIP System on the roof, you don't need roofing paper.
ZIP is a very high grade of OSB. It cuts clean and you never find any voids in it. You can also buy ZIP Panels longer then 8 feet. I've bought 4x9 and 4x12 for walls that I wanted to avoid a small piece or to run it from sill plate to top plates, and from sill plate to the peak of my ridge. This increases the strength of your wall sheathing tremendously!!!
OSB and Plywood require clips if you have 24 inch centers for your rafters or trusses.
Both brand new OSB and Plywood will hold the nails in place just fine. The nail has to go all the way through the OSB or Plywood. The point does not hold the nail in place. The shaft is what holds the nail in place and it needs to be longer then the thickness of the shingle and the OSB or Plywood. 1 1/2 inch nails are the smallest that should ever be used on a roof. Crooked roofing companies will try to use shorter nails to save money, but just like using staples, this leads to failure.
The biggest difference between plywood and OSB is that during nailing, plywood will blow off that bottom layer of material. This is very common and something that I see when I'm up in an attic all the time. I've never seen it so bad that it's the cause of failure, but it is dramatic enough that I will never use Plywood for roof decking. When that bottom layer is gone, you will often see that there is a huge void there too, so the nail is only being held in place by one layer of material, or a third of half an inch. What is the math on that? For me, OSB is far superior to Plywood on this issue.
Something that I see too often in houses, is people having half inch sheetrock on their ceilings with 24 inch centers. This leads to sagging and even cracking in the ceiling over time. 5/8's sheetrock has to be used for 24 inch centers. With a fairly smooth texture on the ceiling and paint with a little bit of reflection, this becomes obvious. This is also why flat paint and thick texture, like popcorn, was so popular for so long. It hides the imperfections that come from using half inch sheetrock on ceilings.
RickB
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We were fortunate. And my math says they were 28 years old when we sold it.
Cat_Driver
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All you needed know ...
https://www.greenbuildingadvisor.com/app/uploads/sites/default/files/Plywood-vs-OSB_FHB169.pdf
https://www.greenbuildingadvisor.com/app/uploads/sites/default/files/Plywood-vs-OSB_FHB169.pdf
RickB
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15 years ago.
Snobdds
Elite Member
Modern plywood has too many voids in it that crush when a fastener goes through it. Kinda hard to cover a huge dimple...
I use OSB for walls and roof.
I think something nobody has hit on is the pull out resistance between OSB and plywood. Go drive a ring shank nail in OSB and plywood. The OSB will be much harder to pull out than plywood.
I use OSB for walls and roof.
I think something nobody has hit on is the pull out resistance between OSB and plywood. Go drive a ring shank nail in OSB and plywood. The OSB will be much harder to pull out than plywood.
