OSB Wall Sheathing

[kurt]

We took a scrap of Advantech floor decking and placed it in a bucket full of water for two weeks. We removed it and let it dry. The piece seemed unaffected.

I did the same thing for 4 months; same result. Nothing. Still in perfect condition.

So, I don't know how it works sometimes, but not others.

Rocon, what do you think were the mitigating factors in the breakdown of the material you saw?

[mgbinspect]

Like any engineered material, it has to be used in a design specific manner. Which, of course, rarely happens.

How often do folks see Exposure 1 material being used? How often do you see Exposure 2 for sheathing?

Honestly, I hardly ever see the stuff. I've built with it, but I don't see it all that often on other than for reroofing over skip sheathing.

My photos are of exposure 1 rated OSB installed in 2004.

It seems that once the water is introduced to the OSB the lignan breaks down very quickly. The adhesives seem to have very little resistance to moisture.

I don't know of any wood based material that can survive the environment your photos reflect for very long. We all know that once you put such materials in a warm moist failry sealed environment, it's pretty much doomed.

All things considered, I think OSB does fantastic, and the photos are more a statement about the environment than OSB. Think about it: you're looking at OSB after seven years in the nastiest possible situation. Not bad...

[Rocon]

Well there were a lot of issues. The project is in Florida so the rain exposure is high. I would include the following issues for allowing water into the framing.

1. The plaster system is a one coat system installed with one layer of WRB. Its total thickness was less than ½Ã¢â‚¬

[kurt]

Yep........that'd do it.........

[hausdok]

Well there were a lot of issues. The project is in Florida so the rain exposure is high. I would include the following issues for allowing water into the framing.

1. The plaster system is a one coat system installed with one layer of WRB. Its total thickness was less than ½Ã¢â‚¬

[Bain]

I love you all, but this thread amply demonstrates how incredibly OCD WE all are.

I mean, really. Besides us, who sticks a hunk of Advantech in a tub of water just to see what happens?

[Rocon]

Originally posted by Rocon

Well there were a lot of issues. The project is in Florida so the rain exposure is high. I would include the following issues for allowing water into the framing.

quote]Basically all issues that would cause plywood or even wood planking to rot.

OSB is ubiguitous here and has been used for roofs, walls and floor decks for a quarter of a century. If the product were half as bad as what only a quarter of its detractors say, it would have been off the market decades ago.

There are design/use limitations with every building material used and one violates those rules at one's own peril. Most failures I see are the direct cause of someone's screwup.

ONE TEAM - ONE FIGHT!!!

Mike

Correct, unfortunately there was no plywood installed so I could at least take a swag at how they performed in the same assembly side by side. However on another project where plywood left completely exposed to the elements for two years the plywood was still generally intact. The plywood was no longer viable as a shear resisting structural element. Granted the wetting and drying cycle of exposed plywood compared to OSB in an assembly is completely different.

On this project (photos) I saw something that really amazed me. If you look at some of my original photos the OSB is gone but the lumber next to it shows some staining but very little damage to the framing, straps, and nails. Some of the OSB is completely deteriorated between a Simpson strap and framing timber. Somehow I believe that plywood might have performed better. To what degree? Who knows?

I must admit that the OSB on the roof (same project as the photos came from) was nearly pristine. With no water introduced the OSB only showed discoloration from heat… Not a problem.

The issue I have of soaking OSB in a tub for several months is that just introducing water to a material does not create advanced decay; at best you would find delamination of components. The incipient decay I found is from many wetting and drying cycles. The “washingâ€

[kurt]

I think that's possible. Building envelopes can be assembled so they are water tight without vapor or moisture problems. It just doesn't happen very often.

For all the advances in material, there's still no corresponding understanding by the folks that put up buildings. I'm sure this building had architectural "oversight", and look what happens.

[John Kogel]

Since you'all are still kicking this one around, here's some pics from today, OSB sheathing that's been absorbing water for a few years, OSB that's been kept painted, old Fir plywood that's never needed paint, new knotty sapwood plywood on a new building.

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[Tom Raymond]

architectural "oversight"

Ha! That's a hoot. I've yet to work with one that knew what the hell they were doing. The last project I did with an architect was converting the gift shop at the local hospital into a Coffee Culture kiosk. His specs were so far out of whack I had to cut a cabinet in half to make it fit.

[kurt]

Since you'all are still kicking this one around, here's some pics from today, OSB sheathing that's been absorbing water for a few years, OSB that's been kept painted, old Fir plywood that's never needed paint, new knotty sapwood plywood on a new building.

How are you determining the rating, i.e., is this Exposure 1 or 2?

I'm not disputing anything anyone is saying about OSB, but I have a lot of curiosity on how folks are figuring out ratings on material that's installed, covered, inaccessible, or destroyed.

I ask, because on the Advantech that I've put out in the weather, i.e., full exposure to rain, wind, sun, snow, ice, etc., it holds up.

How are you folks determining rating?

[John Kogel]

Since you'all are still kicking this one around, here's some pics from today, OSB sheathing that's been absorbing water for a few years, OSB that's been kept painted, old Fir plywood that's never needed paint, new knotty sapwood plywood on a new building.

How are you determining the rating, i.e., is this Exposure 1 or 2?

I'm not disputing anything anyone is saying about OSB, but I have a lot of curiosity on how folks are figuring out ratings on material that's installed, covered, inaccessible, or destroyed.

I ask, because on the Advantech that I've put out in the weather, i.e., full exposure to rain, wind, sun, snow, ice, etc., it holds up.

How are you folks determining rating?

This was an amateur addition to a decent old house, so I just said rip it off and put a better roof on it. Properly installed OSB roof sheathing has the stamps visible in the attic. Also in Canada, exterior grade OSB has a green painted edge you can sometimes see. It's usually OK, except if it gets wet enough for mold to start growing on it.

[Rocon]

How are you folks determining rating?

For me it is the APA label which we uncovered at several locations.