# OSB and Rain .....



## TexasTimbers

How much rain can OSB (Norbord), used as sheathing take before it will start to delaminate, warp, and whatever else prolonged exsessive moisture will do to it? 
More specifically, I have had the 1 or 2 rains hit my sheathing/decking before, but what will 2 - 3 days of solid rain do to it? 
I realize I must allow it to completely dry out before I wrap it.
I guess I am asking what will happen a years, or years, down the road if anything?


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## Joasis

I have noticed that OSB that has ever been wet will discolor, and it weakens it a lot, as if it had much in structural strength to begin with. I suppose if it was wet, and then protected immediately, it would still be ok...you know, no water, no rot.....the damage would all show up soon.


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## house bldr

OSB on side walls is very resilient to the weather. It wont warp like plywood but will flake somewhat if exposed to a lot of moisture. I always try to house wrap mine asap as a precaution but have seen many big projects such as motels left exposed for months with no ill effects that were of concern to the architect. It will swell quite a bit after it has been wet!Almost everyone in my neck of the woods uses osb for wall sheathing as well as roof decking and 3/4 t&g subfloor.


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## Joe Carola

TexasTimbers said:


> How much rain can OSB (Norbord), used as sheathing take before it will start to delaminate, warp, and whatever else prolonged exsessive moisture will do to it?
> More specifically, I have had the 1 or 2 rains hit my sheathing/decking before, but what will 2 - 3 days of solid rain do to it?
> I realize I must allow it to completely dry out before I wrap it.
> I guess I am asking what will happen a years, or years, down the road if anything?


Is this a house or addition?

Sounds like you new this stuff would warp if it got wet. If so why did you buy this stuff knowing it could cause a problem and cost you alot more money in the long run then if you bought fir plywood.


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## dougchips

TexasTimbers said:


> How much rain can OSB (Norbord), used as sheathing take before it will start to delaminate, warp, and whatever else prolonged exsessive moisture will do to it?
> More specifically, I have had the 1 or 2 rains hit my sheathing/decking before, but what will 2 - 3 days of solid rain do to it?
> I realize I must allow it to completely dry out before I wrap it.
> I guess I am asking what will happen a years, or years, down the road if anything?


You will add character to the siding, the warping will show through. Can you spec your jobs for plywood?


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## TexasTimbers

Joe, it is an addition; please avoid assumptions as much as possible, I'm sure you know how the root word breaks down.  
I did not assume anything of the kind to the extent you seem to imply. Commmon sense tells us that moisture and man made "engineered" products will at some point begin to have a conflict of interests. If I knew when exactly that was and to what degree, I would not have had to post the question. 
I am just trying to take the temperature of others who may have more experience with this product. Even though I have installed many thousands of sheets of it in many different applications, I have nearly always been able to get it wrapped/covered/protected before the rains hit, and I have never had it get rained on for 2 days without ceasing, so I was concerned.
This time for reasons about which I don't wish to elaborate (could drag the thread way off point) I was not able to do it.
I did check the Norbord website but there was no information regarding moisture resistance that I could find.

Thanks for your input fellas.

Edit: this OSB is in the form of SIPs having a 3.5 PU core. I feel that they will not delamintae as PU being about the strongest glue on the planet so i don't believe the moisture can get between the PU and the OSB inner surface, but I was simply wondering what might I expect from the outer surfaces of the OSB.


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## copusbuilder

They must make it different in Texas. I made a scate board ramp for my son a year ago. Damn thing still looks pretty good as it sits in the weather? Try that with fir or ply..
I always hated the crap until I actually used it. Try tha


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## house bldr

We have been using nothing but osb for about the last 10 years and have never seen it warp when nailed on the wall. It will simply have a few flakes lift on the corners.They are practically giving it away now at 5.90 a sheet for 7/16 osb.I just bought 3 lifts of it,wish I had more room I would buy more!


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## TexasTimbers

When Katrina was bearing down on NOLA I bought four 80 sheet lifts for fear of not being able to get any for a while... I still have a couple hundred. 

I was not worried about warpage really even though i used the word. I am mainly worried about flaking and the panels on the south side of the building is flaking a little more than what I think it should but still I am sure it will be fine once covered.


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## leiffearn

Okay, how many of you get those flakes right in the end of your finger below the nail damnit! Thats the only thing I can think of...besides that it smells so funny when you cut it, and if there are cutoffs piled on the ground and you step on them you are on your ass before you knew that you were falling. But if you don't care about the people working for you...hell with it! Go for the OSB! Ha


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## Teetorbilt

Just particle board with bigger chunks. I always look for other things done with a product. Some guys still build plywood raceboats, I have yet to see one made of particleboard or OSB.

Queer sense of humor. Particleboard raceboat slowly disintegrating in a trail of sawdust. Strikes me as funny.


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## TexasTimbers

Yo Teet not trying to get a argument started but if you seriously think OSB and part&*%e board (I hate that stuff so much I can't even type it.) aren't much different you must not have worked with either or one of them very much. 

If you have and still think they are close to the same then put a chunk of each in water, along with a chunk plywood in water overnight. 

Guess which one swells and delaminates the least? OSB. Plywood will swell and delaminate faster than OSB but not as fast as part&*%e board. 

I wasn't asking my question because I was unfimiliar with OSB, I was just lloking for feedback from others. I already know that in situations where moisture will get to the sheathing/decking, I am going to choose it over plywood anytime.
The only time I will choose plywood over OSB is if I need it to be "stouter (it is)" and I KNOW that water/moisture will never get to it.
I do understand builders' reluctance to use it. I hate it when my cheese is moved too. I am a man ...... I eschew chaange! GRRRRRRRR!


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## clampman

I certainly wouldn't worry about it. Especially in SIPs. You know they're using a decent brand.

I know years ago a good buddy of mine framed McMansions up north. They were so big, standing water on subfloors was the norm for days on end. He used to tell the GC's he subbed from that if they used any plywood other than Stimson or Roseburg for subfloors, they would have to hire someone else rip it out after it delaminated. He refused to schedule or do tearouts. Those were the only two brands of plywood that didn't delaminate back then under those conditions. He was fine with any old osb.

Seems like plywood can often be a problem. It must have something to do with the way the glue is put on it when they make it.

The shop maple that CT Plywood carried for about a year in the late '90's was total garbage, and the outer ply would delaminate just sitting in the hot dry shop. I started using that heavy a$$ birch from Home Depot for more money and much more aggravation getting it and sanding it, just because it stayed together. Nothing worse than a call from a "faux" painter telling you the flat panels on your custom cabs are peeling.

My guess is that osb isn't as tasty as regular plywood either for the termites you guys get down there.


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## Steve Unkie

I think that OSB is designed to be able to handle extended construction delays. Now, what is the definition of 'extended construction delays'?
More than 2-3 days of exposure, I'm sure. Your fine.

Steve Unkie.


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## dayspring

I use Advantek :thumbup: OSB for floor and roof sheathing. It took me a long time to make the change from plywood, but I am impressed with the stuff. It also has a 50 year warranty:w00t: , I don't know of a ply that has such.
The regular OSB is different however, it will swell if it smells rain. I do use it, but we cover it ASAP when we do.


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## Joshua

From Louisiana Pacific's website in regard to their warranty...

(iv) The Product cannot have been used in
an exterior exposure or in an interior
space that creates an exterior
environment. The Product may not be
in direct contact with the ground or
used in any application which allows
for the accumulation of condensation
or other free water or which subjects
the Product to a repetitive wetting
condition at any time during the
warranty period other than normal rain
conditions experienced during construction
or installation of the Product.

...I haven't checked, but I'm sure the rest (GP, Norboard, Langboard, etc...) will avoid specifics to leave the door open for release of liability.​


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## Joshua

From Langboard...

Langboard OSB carries an exposure 1 rating. Exposure 1 panels are designed for applications where some construction delays could occur before providing protection.


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## dayspring

All I'll say is... So Far, I Myself have had no, notta, not even any problems with the Advantek. We do not leave it exposed any longer than we have to, but no trouble so far!


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## d.janvrin

Advantek Been using for couple years not bad the only thing ive seen wrong with it is 1 (cutting dusty ,and rough on blades, seen sparks from blade.) 2 Mason dropped a stone :no: (apx 40lbs)from fireplace mantel Wall (apx 10' high)went through it like it wasn,t even there:blink: . VERY HARD to Patch. Patch has to be at least 32"X32" any thing smaller bends on 16oc joist, note Stone fell through 2nd floor (Advantek) stopped on first floor plywood :thumbup: both 3/4 . happened on weekend masons were only one in home :notworthy new construction . 

Oh Yea OSB No Problems . have seen it wet for weeks at a time if nailed of tight its fine.
even used for walk way scrapes,through the muck dont fall apart as soon as plywood, Im on seacoast NH ,Ma. our OSB has 1 side chips untreated 1 side has some kind of coating plastic ?? fiberglass?? that side goes out to weather side . does yours?? Thanks Dave


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