Having a home built. Being a construction idiot I'm trying to inhale everything I can about materials. Between OSB vs Plywood, insulated studs, high grade siding, house wrapping and more, I've come to the conclusion that you probably can double the purchase price of any home depending on materials used. Next week I meet with the main man for the first time, on the 2 acre parcel we have. He'll be my contact throughout the building process. Already having signed a purchase agreement, he can surely talk circles around any concerns I might have while being considerate and professional, so I fear my concerns won't change a thing. It all comes down to where I want the money to be spent, inside and outside I guess.
Curious as to your thoughts on the mixing of OSB and plywood on an existing roof deck. In performing some assessments, we come across situations where damaged plywood panels were replaced by OSB. My preference as an engineer would be for uniformity across an area. Wood engineering and construction is already a science of variability. Adding variability is a nightmare, even if testing. While one would hope that any adverse impact may be slight, it probably is a function of the ratio of area replacement as well as the location. In design, added unpredictability results in an increase in the factor-of-safety. Always a challenge facing unconventional construction techniques, particularly those of the DIYers.
What happens when you install underlayment and shingles on top of a soaking wet roof decking? The roofers patched 2 areas maybe 4x4 decking with OSB and the outer soffit area - the part you see with APA 32/16 exposure 1 - Thickness 0.451, 15/32 Category. I read that off the plywood. And is it even more compromised with a ton of bad empty knot holes and just crappy, splintery wood? I watched the wood as the roofers walked onI it. Glad they didn’t fall through. I am trying to learn as much as I can about wood, the weather and roofing. Thanks
I'm enclosing a carrport to better protect my car and create a small workshop. I have T-111 plywood sheathing with a Behr wood stain on the exterior, and I'm trying to decide on what sheathing to use to finish the interior -- plywood or OSB. Any suggestions? Thanks.
I have a shingled roof right now with 7/16 OSB. When it's time to replace, I was thinking of going with metal, but it sounds like to pullout values are too low, so it wouldn't be a good idea. What if diagonal furring strips were layed down first, and screwed right into the joists? Would those strips then have adequate holding strength and make this feasible? If so, how significantly would this add to the cost?
Diagonal laid strapping on top of the sheathing, with Coravent on three sides, provides under-metal ventilation to the ridge. The strapping holds the metal roof fasteners better than either plywood or OSB, and it vents moisture out, to keep things dry under the metal. Cover the sheathing with a self stick smart vapor membrane, and the sheathing will dry through it.
You definitely want an underlayment installed so you can have your plywood dried-in before the metal goes on. Here's a video you can check out about the differences between felt, synthetic, and fully adhered underlayments: bit.ly/metal-roof-underlayment-video -Thad
Thanks so much, Robert! Here are some things to consider with the Zip System: I would always continue to use an underlayment no matter what. These Zip products need to be taped and rolled at the seams correctly, seams have to have proper spacing, and all over-driven nails need to be sealed. There is a chance some areas might be missed, so using a quality peel & stick as a secondary defense is always good practice. If you decide to use the underlayment, I would compare the cost of using the traditional *plywood with underlayment* vs. the *Zip System with underlayment* and see if the benefits outweigh the price. Secondly, a lot of ZIP Systems are 7/16” OSB which may not be suitable for roof decking. My suggestion for roof decking is ½” minimum plywood or 5/8” OSB which are close in fastener pull-out values and far exceed 7/16” OSB decking. -Thad
The Metal Roofing Channel not disagreeing with your main point, just pointing out that they do offer 1/2” and 5/8” Zip sheathing for roofs (and walls). Those panels have a rusty brown color instead of green. My question is, have you worked with Advantech wall and roof sheathing? Made by the same company that makes Zip sheathing. I know their subfloor sheathing has phenomenal strength and water resistance but it looks like it carries over to their roof and wall sheathing as well. Talking about a 10% increase in bending and pullout strength compared to CDX plywood of the same thickness.
My current wood shake roof has space decking with 1 x 6’s, could I re-roof with a metal roof without having to install plywood or OSB? Assuming I am removing the shingles but leaving the space decking
You're probably not going to find engineering if you go over a spaced substrate. Double check with whichever manufacturer you decide to go with, but my guess is they will probably steer you towards a solid substrate like plywood or OSB. A solid deck would allow freedom to space clips at the required distances and would also give the contractor the ability to address any venting concerns now that your shakes have been removed. -Thad
As a dirt poor DIY home builder over 30 years ago I was talked into "7/16s OSB is just as good as 1/2 inch CDX" ... wow the pull out fastener difference blew my mind. OSB has no place on a roof...
Does pullout values matter when you are installing on an enclosed structure such as a house. Just seems like something that would only matter in relation to things such as pole barns
Yes, it matters because that is how the strength of your attachment is measured, and wind uplifts affect all buildings. You can learn more about pull-out values here: bit.ly/fastener-pull-out-values-video -Thad
I am thinking about metal roof. I have couple of questions for you: Which one is better 7/16 plywood or 5/8 plywood ? Is 7/16 sufficient or should we go with 5/8 ? Between 5/8 OSB and 7/16 plywood which option is better ? I will highly appreciate your response.
Do you keep track of contractors using Sheffield metals for walls and/or roofs? Do you have any quality measurements you track for your installation contractors. I live 40 miles S of Chicago.
We can recommend a number of installers in your area if you are currently searching for one. Drop us a line and we can answer any additional questions and get more specific information: bit.ly/contact-sheffield -Thad
Metal should always be installed over battens that's what gives you your energy star rating real wood also holds the screw approximately five times longer then plywood or OSB don't doubt me on this
Our GC has talked repeatedly how our house has been over-engineered. We have 3 steel I-beams, zip system on walls, Advantech sub floors with gorilla glue and just found out he installed 1/2” OSB on our roof! We have a standing seam metal roof being installed. Also, the Tarco NR600 membrane is wavy and lifting up on two peaks. What do you think we should do? This roof is very expensive and was purchased for longevity. I’m afraid we won’t get the longevity with what is currently happening and given the decking thinness.
If the GC didn't follow the specs, then you can sue him for the cost of ripping off the deck and roofing materials and replacing it all per spec. If there weren't any specs for deck materials, then you are stuck. If you are not in an extreme weather area, it will probably be ok, especially if the roofing material is high quality. When the roof finally needs to be redone, you can think about having the deck redone too, though it will be a significant additional expense.
If you used a layer of rigid foam over your roof sheathing, would you need a second layer of roof sheathing over the rigid foam to screw the roofing to? Or would you use longer screws that go through the foam?
Hey, Bradley! Overall, it would depend entirely on how the system was tested and engineered. Typically, you would use longer screws. The compression strength of the ISO and the size of the clip base you are using would determine whether or not you would need a bearing plate under the clip so it doesn’t crush the ISO when you fasten the clip down. Hope this helps! -Thad
Is there any reason not to use 7/16 OSB for roof decking when it's being used to sheet over the existing shiplap roof deck? This is for a composite shingle roof
The 7/16 OSB would be additive to your existing roof deck. Finished thickness would be over 1" which would be more than adequate. You could use construction adhesive between layers to get a more uniform performing deck. Mark/chalkline all the rafters and run a 2" to 2 1/2" screw into them spaced 8" to secure the top and bottom layers.
For what fastener? To my knowledge, pull-out values for the fasteners we use (for wooden roof decking) are primarily tested on OSB, plywood, and SYP (2x4). I can do a bit more digging if you can give me some additional specifics on the assembly. -Thad
Omg. Please do not say that. I'm broken, I'm d.i.y., I'm only finishing an edge of this as a correction ( I hope) from where the water backed up into it and into my walls. I'm horrified. But have no choice. My husband had a stroke/s. And I've got less than 3 days before torrential rain comes back. It's hard by myself. It's hard period. Prayers needed/appreciated.
In my experience, plywood ages much better... and if it gets a little wet (not completely soaked for a long time), it can survive for reuse with much less swelling. Get OSB damp, and it's trash. I'd say if you have an application where you want it to be repairable and have more durability, go for plywood. Double the cost? Still worth it.
I know that OSB is relentlessly pushed in the USA. I prefer for all outer surfaces plywood, that is roof and outer cover of the outside walls.. Plywood is more impact resistance than OSB. On the inside I prefer OSB, it does not carry sound like plywood. My roof would have on top of the beams 12 or 15 mm plywood, than 2 x 2 stringers following the beams, covered by 1 x 6, than tar paper than galvanised corrugated steel, round, the thickest available, screwed down.
Neither osb or ply are great choices, best results are to be found using traditional sarking , that’s rough sawn timber boards, (treated,) this is the traditional form of roofing finish to take slate in Scotland, note not in England, this is more reliable than particle board, which is prone to deterioration if subjected to moisture. OSB will blow & lose its structural integrity & ply will tend to delaminate. The sarking will also take nailing for fixing to the roof frame with a much higher resistance to pulling out as the cellulose fibres in the timber have a tension that the particle boards don’t have. In exposed areas or locations that experience high winds this offers a far more robust roof frame, the sarking also gives the roof frame greater lateral strength than sheathing that combined with good detailing, such as ties to mitigate against lift, etc will give you the best results & if the workmanship is of a decent standard will last for a very long time, more than a lifetime. I’m based in Scotland but heading over to the States in the very near future. Texas to be precise. We are very experienced builders particularly using traditional building techniques, including natural stone walls built using traditional lime mortars. Our company is Cameron Building Services, based in Scotland you can Google us if you are interested
Yes, I agree with plywood I would make that extra investment and use pressure treated plywood. Now for the tight wadds out there that wants to pocket the money by taken short cuts again the cheap comes out expensive at the end the price difference between regular plywood and pressure treated plywood is worth the investment long run..when constructing.a structure you can't have a mind frame well if I buy the lowest quality materials I can pocket more money your mindset should be what materials high quality that will last long term for the comment I received claiming that I'm waisting money have said that if I built my home too last by using high quality long lasting materials would you want me too build your.house using my mindset of a shortcut mindset. Best Regards,
Why not use treated plywood? It is rot and termite proof. The roofing might fail but the deck won't. Fasteners do need to be hot-dipped galvanized or stainless steel and care must be taken about metals in contact, but this is all manageable. Standard CDX is only capable of withstanding short-duration weather exposure, and OSB not at all.
i believe the wood used for OSB is a lighter density soft crappy fast growing junk wood, plywood generally is fir. much better quality . i wouldn't believe sales people, most of them seem to glorify OSB when it is clearly junk.
Please don't tell me that OSB3 is equivalent to marine plywood. Wherever the water touches it, it swallows like women's tampon. Once in place it just rot away. You get what you pay for.
Here in the Puget Sound region (Seattle) I'm going with the plywood decking for my home. Thanks for the info and clarifications on these materials.
My dad installed 3/4" plywood on our roof more than 20 years ago. The roof still looks great with no issues.
Awesome that’s what I’m getting ready to put on my cabin as a roof
Wise man. Plywood is wise idea. People get cheap and too thrifty and settle for OSB. I would not want any OSB on my home no thanks
I am going to have my roofing contractor to install 3/4" plywood after the hurricane IAN.
Having a home built. Being a construction idiot I'm trying to inhale everything I can about materials. Between OSB vs Plywood, insulated studs, high grade siding, house wrapping and more, I've come to the conclusion that you probably can double the purchase price of any home depending on materials used. Next week I meet with the main man for the first time, on the 2 acre parcel we have. He'll be my contact throughout the building process. Already having signed a purchase agreement, he can surely talk circles around any concerns I might have while being considerate and professional, so I fear my concerns won't change a thing. It all comes down to where I want the money to be spent, inside and outside I guess.
Curious as to your thoughts on the mixing of OSB and plywood on an existing roof deck. In performing some assessments, we come across situations where damaged plywood panels were replaced by OSB. My preference as an engineer would be for uniformity across an area. Wood engineering and construction is already a science of variability. Adding variability is a nightmare, even if testing. While one would hope that any adverse impact may be slight, it probably is a function of the ratio of area replacement as well as the location. In design, added unpredictability results in an increase in the factor-of-safety. Always a challenge facing unconventional construction techniques, particularly those of the DIYers.
What happens when you install underlayment and shingles on top of a soaking wet roof decking? The roofers patched 2 areas maybe 4x4 decking with OSB and the outer soffit area - the part you see with APA 32/16 exposure 1 - Thickness 0.451, 15/32 Category. I read that off the plywood. And is it even more compromised with a ton of bad empty knot holes and just crappy, splintery wood? I watched the wood as the roofers walked onI it. Glad they didn’t fall through. I am trying to learn as much as I can about wood, the weather and roofing. Thanks
I'm enclosing a carrport to better protect my car and create a small workshop. I have T-111 plywood sheathing with a Behr wood stain on the exterior, and I'm trying to decide on what sheathing to use to finish the interior -- plywood or OSB. Any suggestions? Thanks.
I have a shingled roof right now with 7/16 OSB. When it's time to replace, I was thinking of going with metal, but it sounds like to pullout values are too low, so it wouldn't be a good idea. What if diagonal furring strips were layed down first, and screwed right into the joists? Would those strips then have adequate holding strength and make this feasible? If so, how significantly would this add to the cost?
We need comparison between cementitious waterproofing and Roll bitumen.
Diagonal laid strapping on top of the sheathing, with Coravent on three sides, provides under-metal ventilation to the ridge. The strapping holds the metal roof fasteners better than either plywood or OSB, and it vents moisture out, to keep things dry under the metal. Cover the sheathing with a self stick smart vapor membrane, and the sheathing will dry through it.
Metal roof will be too hot in Summer in Florida.
Thank you for your video. Is the plywood is a better quality than OSB?
Great explanation
Glad it was helpful! -Thad
Thank you for the tutorial, but can I lay the metal directly on top of the plywood deck if I place roofing felt between the two materials? Thank you.
You definitely want an underlayment installed so you can have your plywood dried-in before the metal goes on. Here's a video you can check out about the differences between felt, synthetic, and fully adhered underlayments: bit.ly/metal-roof-underlayment-video -Thad
You helped me make my choice for plywood. Im also interested in your opinion on the new magic Zip osb board? Thanks for your channel!
Thanks so much, Robert! Here are some things to consider with the Zip System: I would always continue to use an underlayment no matter what. These Zip products need to be taped and rolled at the seams correctly, seams have to have proper spacing, and all over-driven nails need to be sealed. There is a chance some areas might be missed, so using a quality peel & stick as a secondary defense is always good practice. If you decide to use the underlayment, I would compare the cost of using the traditional *plywood with underlayment* vs. the *Zip System with underlayment* and see if the benefits outweigh the price. Secondly, a lot of ZIP Systems are 7/16” OSB which may not be suitable for roof decking. My suggestion for roof decking is ½” minimum plywood or 5/8” OSB which are close in fastener pull-out values and far exceed 7/16” OSB decking. -Thad
The Metal Roofing Channel not disagreeing with your main point, just pointing out that they do offer 1/2” and 5/8” Zip sheathing for roofs (and walls). Those panels have a rusty brown color instead of green. My question is, have you worked with Advantech wall and roof sheathing? Made by the same company that makes Zip sheathing. I know their subfloor sheathing has phenomenal strength and water resistance but it looks like it carries over to their roof and wall sheathing as well. Talking about a 10% increase in bending and pullout strength compared to CDX plywood of the same thickness.
Can you include plank decking ? Or do another video with that. Seems like the planks are of higher quality and better decking. Thanks
My assumption is that is the best option, however much more expensive, hence reason shift to 4x8 sheet goods.
My current wood shake roof has space decking with 1 x 6’s, could I re-roof with a metal roof without having to install plywood or OSB? Assuming I am removing the shingles but leaving the space decking
You're probably not going to find engineering if you go over a spaced substrate. Double check with whichever manufacturer you decide to go with, but my guess is they will probably steer you towards a solid substrate like plywood or OSB. A solid deck would allow freedom to space clips at the required distances and would also give the contractor the ability to address any venting concerns now that your shakes have been removed. -Thad
If you find 7/16 OSB, can you just put in more screws?
As a dirt poor DIY home builder over 30 years ago I was talked into "7/16s OSB is just as good as 1/2 inch CDX" ... wow the pull out fastener difference blew my mind. OSB has no place on a roof...
Any good Carpenter/builder would never use 7/16" osb on a roof, use 5/8 or 3/4
@@R_B62 Agree! 3/4" is the best.
Does pullout values matter when you are installing on an enclosed structure such as a house. Just seems like something that would only matter in relation to things such as pole barns
Yes, it matters because that is how the strength of your attachment is measured, and wind uplifts affect all buildings. You can learn more about pull-out values here: bit.ly/fastener-pull-out-values-video -Thad
I am thinking about metal roof. I have couple of questions for you:
Which one is better 7/16 plywood or 5/8 plywood ? Is 7/16 sufficient or should we go with 5/8 ?
Between 5/8 OSB and 7/16 plywood which option is better ?
I will highly appreciate your response.
I'm pretty sure he said in the video 5/8 would be the stronger option especially if you're going over Rafters that are 2 ft on Center
Do you keep track of contractors using Sheffield metals for walls and/or roofs? Do you have any quality measurements you track for your installation contractors. I live 40 miles S of Chicago.
We can recommend a number of installers in your area if you are currently searching for one. Drop us a line and we can answer any additional questions and get more specific information: bit.ly/contact-sheffield -Thad
Metal should always be installed over battens that's what gives you your energy star rating real wood also holds the screw approximately five times longer then plywood or OSB don't doubt me on this
Our GC has talked repeatedly how our house has been over-engineered. We have 3 steel I-beams, zip system on walls, Advantech sub floors with gorilla glue and just found out he installed 1/2” OSB on our roof! We have a standing seam metal roof being installed. Also, the Tarco NR600 membrane is wavy and lifting up on two peaks. What do you think we should do? This roof is very expensive and was purchased for longevity. I’m afraid we won’t get the longevity with what is currently happening and given the decking thinness.
If the GC didn't follow the specs, then you can sue him for the cost of ripping off the deck and roofing materials and replacing it all per spec. If there weren't any specs for deck materials, then you are stuck. If you are not in an extreme weather area, it will probably be ok, especially if the roofing material is high quality. When the roof finally needs to be redone, you can think about having the deck redone too, though it will be a significant additional expense.
If you used a layer of rigid foam over your roof sheathing, would you need a second layer of roof sheathing over the rigid foam to screw the roofing to? Or would you use longer screws that go through the foam?
Hey, Bradley! Overall, it would depend entirely on how the system was tested and engineered. Typically, you would use longer screws. The compression strength of the ISO and the size of the clip base you are using would determine whether or not you would need a bearing plate under the clip so it doesn’t crush the ISO when you fasten the clip down. Hope this helps! -Thad
No, never use any decking over the insulation. Use a 3 layer SBS Polyester torch on system. on top of the insulation.
Is there any reason not to use 7/16 OSB for roof decking when it's being used to sheet over the existing shiplap roof deck? This is for a composite shingle roof
The 7/16 OSB would be additive to your existing roof deck. Finished thickness would be over 1" which would be more than adequate. You could use construction adhesive between layers to get a more uniform performing deck. Mark/chalkline all the rafters and run a 2" to 2 1/2" screw into them spaced 8" to secure the top and bottom layers.
@rockymntain this is the comment I been looking for. Thanks man. This is what I wanted to do but wasn't sure. 🤪
what is the pullout value on a 1x6
For what fastener? To my knowledge, pull-out values for the fasteners we use (for wooden roof decking) are primarily tested on OSB, plywood, and SYP (2x4). I can do a bit more digging if you can give me some additional specifics on the assembly. -Thad
why aren't more roof deckings screwed in ? seems like it be stronger than nailed
05/23/2021
I think it would cost less to just nail dollar bills up there
Omg. Please do not say that. I'm broken, I'm d.i.y., I'm only finishing an edge of this as a correction ( I hope) from where the water backed up into it and into my walls. I'm horrified. But have no choice. My husband had a stroke/s. And I've got less than 3 days before torrential rain comes back.
It's hard by myself. It's hard period. Prayers needed/appreciated.
In my experience, plywood ages much better... and if it gets a little wet (not completely soaked for a long time), it can survive for reuse with much less swelling. Get OSB damp, and it's trash. I'd say if you have an application where you want it to be repairable and have more durability, go for plywood. Double the cost? Still worth it.
I just use whatever I find in my local construction dumpster
1 important aspect not covered.. extreme heat like florida for 12 hr days, the lamination in plywood bakes and breaksdown over time unlike osb..
I know that OSB is relentlessly pushed in the USA. I prefer for all outer surfaces plywood, that is roof and outer cover of the outside walls.. Plywood is more impact resistance than OSB. On the inside I prefer OSB, it does not carry sound like plywood. My roof would have on top of the beams 12 or 15 mm plywood, than 2 x 2 stringers following the beams, covered by 1 x 6, than tar paper than galvanised corrugated steel, round, the thickest available, screwed down.
No mention of perm differences...
Neither osb or ply are great choices, best results are to be found using traditional sarking , that’s rough sawn timber boards, (treated,) this is the traditional form of roofing finish to take slate in Scotland, note not in England, this is more reliable than particle board, which is prone to deterioration if subjected to moisture. OSB will blow & lose its structural integrity & ply will tend to delaminate. The sarking will also take nailing for fixing to the roof frame with a much higher resistance to pulling out as the cellulose fibres in the timber have a tension that the particle boards don’t have. In exposed areas or locations that experience high winds this offers a far more robust roof frame, the sarking also gives the roof frame greater lateral strength than sheathing that combined with good detailing, such as ties to mitigate against lift, etc will give you the best results & if the workmanship is of a decent standard will last for a very long time, more than a lifetime. I’m based in Scotland but heading over to the States in the very near future. Texas to be precise. We are very experienced builders particularly using traditional building techniques, including natural stone walls built using traditional lime mortars. Our company is Cameron Building Services, based in Scotland you can Google us if you are interested
Yes, I agree with plywood I would make that extra investment and use pressure treated plywood. Now for the tight wadds out there that wants to pocket the money by taken short cuts again the cheap comes out expensive at the end the price difference between regular plywood and pressure treated plywood is worth the investment long run..when constructing.a structure you can't have a mind frame well if I buy the lowest quality materials I can pocket more money your mindset should be what materials high quality that will last long term for the comment I received claiming that I'm waisting money have said that if I built my home too last by using high quality long lasting materials would you want me too build your.house using my mindset of a shortcut mindset. Best Regards,
Pressure treated plywood is way Overkill also it off gases some pretty toxic fumes
Y not us treated plywood
Why not use treated plywood? It is rot and termite proof. The roofing might fail but the deck won't. Fasteners do need to be hot-dipped galvanized or stainless steel and care must be taken about metals in contact, but this is all manageable. Standard CDX is only capable of withstanding short-duration weather exposure, and OSB not at all.
I just installed 3/4" plywood roof deck on my house and it collapsed. Thanks, I got cards all over my floor.
Was it too heavy? I am planning to do my whole roof.
i believe the wood used for OSB is a lighter density soft crappy fast growing junk wood, plywood generally is fir. much better quality . i wouldn't believe sales people, most of them seem to glorify OSB when it is clearly junk.
OSB is cheap material.
18 mm waterproof. Kronospan. 40 year life.
how about cardboard?
That is fine, just add multiple layers (25) with 100% coverage of each layer with Gorilla Glue.
Add water to that and boom,you'll find out comes to the bottpm
Please don't tell me that OSB3 is equivalent to marine plywood. Wherever the water touches it, it swallows like women's tampon. Once in place it just rot away. You get what you pay for.
And he should take any more. Education
yea cheap.... 30 dollars a sheet,
OSB, don't you mean old BS. OBS.
Osb is absolute junk and shouldn't be used
1930 senconds hahahaha wtf