Osb ?

[finn]

I don't know where the 1991 date came from, as we built our house in 1990 using 1/2" osb for roof sheathing. It came from a local osb mill.

We reshingled a year and a half ago, and the original sheathing was perfect.

Local code now calls for 5/8" on the roof because of the heavy snow loading here, but there is no warping or sagging on my twenty six year old roof.

I haven't seen a plywood roof in new construction in fifteen years.

 

[jevoy]

I used 5/8" osb t&g on my roof. It was about 10$ cheaper than 1/2" plywood per sheet. 24" o.c trusses. T&g makes a much stronger roof and no messing with roof clips.

 

[jevoy]

Only downfall imo is that osb is much heavier to handle than plywood.

 

[Bill Anderson]

Only downfall imo is that osb is much heavier to handle than plywood.

From UMASS-Amherst paper:

"The weights of osb and plywood are similar: 7/16-inch osb and 1/2-inch plywood weigh in at 46 and 48 pounds. However, 3/4-inch Sturd-I-Floor plywood weighs 70 pounds, 10 pounds less than its osb counterpart."

Must be the higher density of 3/4" t&g osb, that adds the +10lbs compared to 3/4 t&g ply.
But wall and roof sheating are similar in weight, according to the Amherst paper.

 

[Casey69]

cheapie cookie-cutter houses & six figure houses all use OSB. never seen a new home use plywood for anything.

i'm guessing any OSB problems could be related to early versions of it, where adhesives weren't as good?

 

[Bill Anderson]

I don't know where the 1991 date came from, as we built our house in 1990 using 1/2" osb for roof sheathing. It came from a local osb mill.

We reshingled a year and a half ago, and the original sheathing was perfect.

Local code now calls for 5/8" on the roof because of the heavy snow loading here, but there is no warping or sagging on my twenty six year old roof.

I haven't seen a plywood roof in new construction in fifteen years.

Hi Finn, I got that date from the UMASS paper. But I'm sure some manufacturers got a jump start, and started production/sales earlier than others. You must have got some of the first OSB produced, and just missed the tail end of the waferboard era.

 

[TractorJeff]

OSB is ten times better than chipboard/waferboard!
As far as plywood, its all about the cost verses its quality.
IMOOC: OSB is a super product based on its qualities against similar priced plywood.

 

[jevoy]

I have lugged many sheets of 1/2" plywood and many sheets of 5/8" osb and the osb is much heavier.

 

[SH7mi]

I used 5/8" OSB on my roof, rafters are 16" oc . The 'H' clips are normally used for OSB when rafters are 24" oc here in Pa.
I would not use OSB as flooring, ever! I framed houses for some nation wide house builders (Toll Bros) and they use it as flooring. I have witnessed 8' 2x4s dropped from 10' and puncture thru the OSB, not happening with 3/4" CDX t&g.

 

[finn]

It's definitely osb. We pulled a sheet for access for some insulation modifications while the shingles were stripped as part of the re-roofing project.

The mill is in Sagola, Michigan, about 60 miles from here.

I assume that's where the product was produced.

 

[Bill Anderson]

I used 5/8" OSB on my roof, rafters are 16" oc . The 'H' clips are normally used for OSB when rafters are 24" oc here in Pa.
I would not use OSB as flooring, ever! I framed houses for some nation wide house builders (Toll Bros) and they use it as flooring. I have witnessed 8' 2x4s dropped from 10' and puncture thru the OSB, not happening with 3/4" CDX t&g.

Okay, SH7mi, you just gave me my weekend project Lol. Seriously! I'll test that out, and drop a 2x4 from 10' and see if the 2x4 puts a hole through 3/4" t&g OSB. Something tells me it wi hold up fine, but we'll see.
If that we're true, I'd have to think that it wouldn't pass National Building Code.

And you are talking about 3/4" OSB correct?

 

[Deej-79]

Okay, SH7mi, you just gave me my weekend project Lol. Seriously! I'll test that out, and drop a 2x4 from 10' and see if the 2x4 puts a hole through 3/4" t&g OSB. Something tells me it wi hold up fine, but we'll see.
If that we're true, I'd have to think that it wouldn't pass National Building Code.

And you are talking about 3/4" OSB correct?

We dropped an end of a 25' truss on 3/4 osb decking from 12' up. It did puncture the osb but not badly.

 

[ddawg16]

Interesting how the 'studies' vary.....

I found plenty that show plywood with the advantage...

https://www.nachi.org/osb-plywood.htm?loadbetadesign=0

http://parr.com/weekend-warriors/plywood-vs.-osb-which-is-better/

And this from a roofing company...

http://www.atlasroofing.com/news/article/177

 

[finn]

Interesting how the 'studies' vary.....

I found plenty that show plywood with the advantage...

https://www.nachi.org/osb-plywood.htm?loadbetadesign=0

http://parr.com/weekend-warriors/plywood-vs.-osb-which-is-better/

And this from a roofing company...

http://www.atlasroofing.com/news/article/177

All three or these citations are summaries of press releases.

None of them qualify as a study or technical paper.

 

[SH7mi]

We dropped an end of a 25' truss on 3/4 osb decking from 12' up. It did puncture the osb but not badly.

This happened back in 1993, they may have made improvements to OSB since then. Seeing that first hand, I will never use it
as flooring .

 

[jives]

This Old House visited a hurricane research facility where they shot 2 x 4s out of an air cannon at window protectors. The 2 x 4 shot right through OSB and bounced off plywood.

Around here everyone uses Zip system (coated OSB) for wall sheathing and roof decks.

 

[1991Syclone]

I am ready to start sheathing my roof and am attracted to OSB basicly because of Price. Has anyone used OSB and wished they had not and why?

You're in Florida. Start checking the codes. One thing you're going to want to pay attention to is the nail spacing. It's now code that when a re-roof is done, the entire underlayment has to be renailed as well.

You'll want to get a 4 point inspection after it's all done as a lot of insurance companies are requiring it, and that will entail the inspector measuring how far apart the attachments from the roof deck to the trusses are.

Here's some more information: http://www.floridabuilding.org/fbc/...tion_poc/a3_shingles/0-materials-roofing4.pdf

 

[MushCreek]

When I redid our roof in FL, code was 4" spacing for edge nails; 8" for the field. I built my roof in SC to the same standard, even though we're not in a high wind area. I also used ring shank galvanized nails. I tend to overdo everything I build. I used huge H-10 hurricane clips to anchor my trusses, even though code here is still just toenailed. The inspector laughed when he saw the way my roof was built.

 

[1953mercury]

I use OSB for wall sheathing, never for roofs. OSB does a very poor job of holding screws for metal roofing compared to 5/8 ply. Mike

 

[mjshore]

This is not a reroof it is new construction the building was engineered for 180mph and code only requires 140. I will post pics of tiedown systems. The reason I am asking about OSB is the engineer stated 5/8 OSB or plywood.

Sent from my SPH-L720T using Tapatalk

 

[mjshore]

I use OSB for wall sheathing, never for roofs. OSB does a very poor job of holding screws for metal roofing compared to 5/8 ply. Mike

Thanks mike this is great feedback as I will be using 5v crimp metal roofing in 20ga

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[1991Syclone]

Personally, living in Florida and having family in the construction business, I would recommend you go with plywood over OSB. If this is going to be a long term house, I would invest the extra money for plywood.

The engineer is just spec'ing what's acceptable by code, he's got no interest in the long term durability of your roof. We're going to be getting into the rainy season soon and I, personally, wouldn't want my roof deck of OSB being rained on waiting for tar paper to go down.

 

[kv501]

How many square is your roof that OSB would make a huge cost difference? I was just at my local lumberyard and the difference between 5/8 OSB and 5/8 plywood is $3.77/sheet after tax. Let's assume you have a 1,500 sq ft roof, that's going to be roughly 50 sheets after accounting for some drop. Is a couple hundred bucks going to sway you on OSB vs plywood?

 

[theoldwizard1]

No, the boards very likely werent tightly spaced. ... In my Indiana house there was a solid ~1/2" gap between boards. As mentioned, not only are the boards stronger but they're also much less prone to water damage and easier to replace when damage does occur.

CONCUR ! My gaps are 1/4" - 1/2".

Never thought about the water damage, but I am sure you are correct. Water can drain away and the boards dry out much quicker than plywood or OSB !

 

[James-W]

CONCUR ! My gaps are 1/4" - 1/2".

Never thought about the water damage, but I am sure you are correct. Water can drain away and the boards dry out much quicker than plywood or OSB !

If the water drains away after getting under the shingles and felt paper, it is going to fall between the boards into your attic, probably right on your insulation. Are you sure that is what you want?

 

[Jason280]

I use OSB for wall sheathing, never for roofs. OSB does a very poor job of holding screws for metal roofing compared to 5/8 ply. Mike

You're doing it wrong.

Regardless of your roofing, your screws should be going through the OSB/plywood and into the rafters...not just into the roofing sub material. Of course, you won't be able to get every screw into a rafter, but the majority of them should be...otherwise, you will have issues with screws backing out over time.

 

[MushCreek]

A few comments here. Originally, many roofs were cedar shingles, and the spacing of the roofing boards helped them dry out. The space between them was intentional. While a board roof is plenty sturdy, it doesn't brace the roof from racking like sheet goods do.

In conventional construction, it would be impossible to have most of the roofing screws hit a rafter. If you could manage to line up one row of screws with a rafter, the rest of them would miss, especially using 36" wide metal. Again, in the old days they used purlins, which were horizontal framing members running across the roof, and the tin was attached to those. Barns were (and some still are) built with no roof sheathing at all; just purlins and tin. The downside is that you often get condensation on the inside of a roof built this way.

 

[DonPowers]

My roof deck is 5/8 AdvanTeck over trusses spaced on 2 ft centers. My roofing is standing seam 16" panels with no exposed fasteners. Consequently, the majority of the screws are only in the sheathing. Prior to installing the panels, we adjusted the screw gun settings, using scrap pieces of AdvanTeck, to fully seat the screw without tearing out.

 

[Kpaige]

Ok I did not read every post just some. Here is my input take it for what it is.
"First there is two types of roofs one that leaks and one that will leak" This is a 100 percent false statement! This was my specialty for 20 yrs. I have never been called back to a leak. The only way my roofs will leak is storm or age. Storms ar snot avoidable and age is maintainance and the home owners job.
On with OSB
OSB is deme signally more stable the plywood provided it is dry. OSB that is used in exterior applications such as roofs Etc need to be covered immediately. Nails pull test better in plywood but stapes pull test better in OSB. ANy span over 16" needs clips to help with sagging.
Sagging will occur in both plywood and OSB.
OSB swells when wet and becomes weaker Plywood delaminates and falls apart.
An older house that releases moisture into the attic is better off with OSB over plywood as OSB has a seal coating on the inside which will help protect it where plywood does not.
Have used 3/4 t and g for roofs but word to the wise it is designed for interior there is no vapor seal and it does not have exterior grade adhesive.

Like I said take it for what you will but I had to test all these conditions in the lab for our spec books.

All that being said my garage is lined with 1/2" OSB nailed with ring shank nails primed and painted white. Works well but it does take a lot of paint!

 

[941designs]

I did 1/2" OSB with mid grade Lowes paint on it. Bang for the buck, I loved it.

 

[941designs]

****. I thought OSB walls not roof.