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Old 03-28-2010, 09:23 PM   #1
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Sealing Cuts on OSB?


Getting ready to cut in a ridge vent, and I'm concerned about the oppressive southern humidity damaging the decking once the sealant is cut off of the edge. What's the proper material to seal this edge?

I was thinking Killz on a roller, but spray paint is also an option... I don't need to be neat, as a new roof will be installed right after this is cut and sealed.

Any roofers have recommendations here?

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Old 03-28-2010, 09:52 PM   #2
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Sealing Cuts on OSB?


I have been roofing 20 years and never knew this had to be done...

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Old 03-28-2010, 11:01 PM   #3
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Sealing Cuts on OSB?


I'm sure it doesn't *have to* ... but I know that edges are OSB's achilles heel, that's where the moisture tends to get in and do it's dirty deeds.

I'm sure it's overkill, but that's why I like DIY... I can afford to take the time to overdo details like this.

In your experience, have you noticed if OSB failures tend to occur around the edges?
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Old 03-28-2010, 11:05 PM   #4
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Sealing Cuts on OSB?


I have noticed that OSB failures occur under roof leaks.
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Old 03-29-2010, 08:20 AM   #5
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Sealing Cuts on OSB?


That was good for a LOL.

Nothing like the voice of experience to point out what should be obvious. So, you think my overkill is ridiculous? If you've not seen humidity cause problems at ridge vents, etc I'll leave well enough alone.

I really do appreciate the advice from those who know better.
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Old 03-29-2010, 03:14 PM   #6
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Sealing Cuts on OSB?


I have never seen it myself.
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Old 03-29-2010, 08:39 PM   #7
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Sealing Cuts on OSB?


And well you should worry: "Performance is similar in many ways, but there are differences in the service provided by osb and plywood. All wood products expand when they get wet. When osb is exposed to wet conditions, it expands faster around the perimeter of the panel than it does in the middle. Swollen edges of osb panels can telegraph through thin coverings like asphalt roof shingles.
The term ghost lines or roof ridging was coined to describe the effect of osb edge swelling under thin roof shingles. The Structural Board Association (SBA), a trade association that represents osb manufacturers in North America, has issued a technical bulletin outlining a plan to prevent this phenomenon. SBA correctly indicates that dry storage, proper installation, adequate roof ventilation and application of a warm-side vapor barrier will help prevent roof ridging.
Irreversible edge swelling has been the biggest knock on osb. Manufacturers have done a good job of addressing this issue at the manufacturing facility and during transportation by coating panel edges. But the reality is that builders don’t limit osb use to full-sized sheets. The edges of cut sheets are seldom if ever treated in the field. Houses under construction get rained on. And if you use osb in an area of very high humidity, like over an improperly vented attic or over a poorly constructed crawlspace, you are asking for trouble." http://bct.nrc.umass.edu/index.php/p...d-and-plywood/ http://www.rd.com/19557/article19557.html
Other problems with OSB: http://www.gp.com/build/PageViewer.a...elementid=6132

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Old 03-30-2010, 10:40 AM   #8
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Sealing Cuts on OSB?


Thanks for the links. This renews my concern that this potential issue may be more of a real-world problem in the humid south (where my house is) than in the environment where AaronB has extensive experience.

So, anyone know how I can seal the cut edges?
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Old 03-30-2010, 07:13 PM   #9
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Sealing Cuts on OSB?


If you are seriously concerned about this, you better tear off the entire roof and seal the edges of every sheet.

IMO, it's a ridiculous thought to even consider.
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Old 03-30-2010, 07:33 PM   #10
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Sealing Cuts on OSB?


The factory already sealed the edges on the uncut sheets (that's what the paint is for) ... but I think I found the evidence I needed to sleep tight with unsealed edges: the cut at the existing power vent, which has been pumping out humid Atlanta air for 20 years shows no significant swelling.

I'm gonna pass on the paint.

Thanks everyone for your advice on this!
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Old 03-30-2010, 07:37 PM   #11
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Sealing Cuts on OSB?


One more thought to consider. Is ridge venting the optimum way for you to go with your roof. There are many thoughts and opinions pro and con about ridge venting.
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Old 03-30-2010, 07:38 PM   #12
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Sealing Cuts on OSB?


Uh oh... Tell me why NOT to ridge vent.
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Old 03-30-2010, 08:18 PM   #13
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Sealing Cuts on OSB?


Strong winds can blow rain into a ridge vent
We've had some really strong rainstorms & I haven't had a problem
But it can happen - poorly designed/installed model
Some roofers will say that any roof pentration will eventually leak
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Old 03-31-2010, 08:00 AM   #14
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Sealing Cuts on OSB?


I thought about the wind-driven rain... the prevailing wind blows parallel to my ridgeline, so I think that will help minimize that problem. I'm using Cobra Rigid Vent III, seems like a decent design, but I don't have experience with these.

Cutting as soon as I post this, installing Friday afternoon.
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Old 03-31-2010, 08:04 AM   #15
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Sealing Cuts on OSB?


Yeah most of the wind blows parallel to my ridge vent too
We have trees pretty much all around the property that helps cut down the wind too

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