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Flaky OSB Roof Sheathing


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Inspected a 1985 home today with flaky OSB roof sheathing under the eaves. The sheathing has been painted/stained, but the flaking is the OSB itself, not the paint/stain. Roof covering is new and the OSB looks good in the attic. Any ideas how to call this?

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Hi,

Sure, it's rotting. Betcha there wasn't any drip edge at the perimeter of the roof either, just like 99.9% of the other roofs around here. I find about 1 out of every homes without drip edging at the eaves has some rot around the perimeter of the roof.

Call it. They'll have to strip it back to the wall line, replace the rotting decking, this time using drip edging, and reshingle the roof. Then they'll have an ugly light-colored band at the perimeter of the roof.

1985 home though. Is it the original cover? If so, strip the whole thing.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Hi,

Sure, it's rotting. Betcha there wasn't any drip edge at the perimeter of the roof either, just like 99.9% of the other roofs around here. I find about 1 out of every homes without drip edging at the eaves has some rot around the perimeter of the roof.

Call it. They'll have to strip it back to the wall line, replace the rotting decking, this time using drip edging, and reshingle the roof. Then they'll have an ugly light-colored band at the perimeter of the roof.

1985 home though. Is it the original cover? If so, strip the whole thing.

ONE TEAM - ONE FIGHT!!!

Mike

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Probed the sheathing, but nothing appears to be rotten -- just surface flaking of the OSB on the underside of the eaves and the flaking appears superficial. Edges looked good. Current asphalt composition shingle covering is new. Could the flaking be the result of moisture intrusion that occurred before the new covering was installed? Or is the flaking characteristic of early generation OSB? And is replacement of the sheathing really necessary? (OSB looks structurally sound.)

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Originally posted by veitenm

Probed the sheathing, but nothing appears to be rotten -- just surface flaking of the OSB on the underside of the eaves and the flaking appears superficial. Edges looked good. Current asphalt composition shingle covering is new. Could the flaking be the result of moisture intrusion that occurred before the new covering was installed? Or is the flaking characteristic of early generation OSB? And is replacement of the sheathing really necessary? (OSB looks structurally sound.)

Every time I've seen painted OSB exposed at the eaves, it looks like it's flaking. I think that's just a characteristic of the product.

- Jim Katen, Oregon

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Originally posted by veitenm

Current asphalt composition shingle covering is new. Could the flaking be the result of moisture intrusion that occurred before the new covering was installed? Or is the flaking characteristic of early generation OSB?

Well, I don't think 1985 is early generation. I seem to recall reading a comparison between plywood and OSB about 8-9 years ago that said that it had been in use (at that time) about three decades.
Every time I've seen painted OSB exposed at the eaves, it looks like it's flaking. I think that's just a characteristic of the product.

- Jim Katen, Oregon

Jim has a point. Plenty of builders around here use plywood at the 2ft. projection at the eaves and deck the rest of the roof in OSB. Perhaps this is the reason; to tell you the truth, I've never thought to ask any of them about it.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Every time I've seen painted OSB exposed at the eaves, it looks like it's flaking. I think that's just a characteristic of the product.

- Jim Katen, Oregon

Jim has a point. Plenty of builders around here use plywood at the 2ft. projection at the eaves and deck the rest of the roof in OSB. Perhaps this is the reason; to tell you the truth, I've never thought to ask any of them about it.

There's at least one local inspector who believes that exposed OSB at the eaves is "against code" because the OSB isn't supposed to remain exposed to the weather. I don't completely share his viewpoint, but it's not entirely without merit.

- Jim Katen, Oregon

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Originally posted by Jim Katen

Originally posted by hausdok

Every time I've seen painted OSB exposed at the eaves, it looks like it's flaking. I think that's just a characteristic of the product.

- Jim Katen, Oregon

Jim has a point. Plenty of builders around here use plywood at the 2ft. projection at the eaves and deck the rest of the roof in OSB. Perhaps this is the reason; to tell you the truth, I've never thought to ask any of them about it.

There's at least one local inspector who believes that exposed OSB at the eaves is "against code" because the OSB isn't supposed to remain exposed to the weather. I don't completely share his viewpoint, but it's not entirely without merit.

- Jim Katen, Oregon

I often find it used to sheath the underside of bumpouts - frequently very close to the soil and unprimed and unpainted. Most of the time it's fine - even after many years - but sometimes it's rotting and needs to be replaced. The stuff that's unpainted is usually turning gray after years of exposure without being painted but unless it's actually rotting seems to be fine. However, I invariably tell them to clean, prime and paint the stuff.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by Richard Stanley

bumpouts - bum pouts, bump outs ?

I don't know if we have those in Texas. What the hell is that / are they???

It's just what it sounds like. A portion of the building that "bumps out" from the wall -- it just projects into space. They were a very common feature on arts & crafts/craftsman bungalows in the teens & twenties.

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Dining room bumpouts on bungalows, zero-clearance fireplace bumpouts on new homes, etc. Want to see a real outrageous one? Check out the photo below; the one on the left is for the direct-vent fireplace and then you have the mongo one over the entry.

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OT - OF!!!

M.

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Mike O,

I'm from Texas and I could easily relate the term "bumpout", to what we call "boxed out", as in a boxed out window. Or at least that is the term that was used when I was supervising the construction of new homes back in the early 80's.

Mike M

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Hi,

Yeah, well sure, the construction field, like everything else, suffers from regional differences in terminology. For instance, if I were to start talking about how the window splines had been installed incorrectly around a window, a builder in upstate New York or New England might know exactly what I'm talking about but out here in the West coast they just look like a deer caught in the headlights and go, "Huh?" Then when you explain it to them they go, "Oh, you mean flashings! Hell, why didn't you just say so?"

ONE TEAM - ONE FIGHT!!!

Mike

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