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masonbrown 10-09-2012 07:55 AM

How to determine if OSB decking should be replaced
After having a "professional" install a replacement roof a year ago, I'm in the process of removing what was installed a section at a time and installing a proper replacement roof. By the crew chief's own admission, they simply installed new shingles over rotten decking in several places, something I intend to correct.

I'm looking for some advice on determining which OSB decking boards should be replaced. Obviously rotten (buckling and/or deteriorated) boards are a no-brainer, but what about less-obvious damage? I have read that OSB is very vulnerable to warping from moisture and I've found a few spots where the edges of the boards seem to be bulging out some, but these boards don't seem structurally unsound when pushing on them in several spots.

Any advice? Thanks!


Windows on Wash 10-09-2012 08:14 AM

If there is edge creep or deflection in the panel, replace it.

joecaption 10-09-2012 08:18 AM

If there turning black that's mold and they have to go.
Where are you looking for signs of damage?

masonbrown 10-09-2012 11:05 AM

2 Attachment(s)
On this particular section (above the garage door) the bottom of the boards isn't accessible from the attic so I'm looking exclusively at the top (after having removed all the underlayment, nails, etc) so far. I'm attaching a couple of photos to show what I'm dealing with, hopefully that helps clarify things.

Thanks for the replies...


joecaption 10-09-2012 11:17 AM

I'm not seeing any rot in those pictures. The black just looks like old tar paper smuges.

Windows on Wash 10-09-2012 01:01 PM


Don't see anything wrong there either.

GBrackins 10-09-2012 04:01 PM

me either

Davejss 10-09-2012 07:01 PM

Looks fine.

joecaption 10-09-2012 07:26 PM

I'm not in love with the way it was flashed at the wall, if it was going to fail anyplace that's where it would be.

How did you happen to be talking to the lead man and find out about roofing over the rotten wood?
Any chance he's not working for that company anymore and is trying to cause trouble?

ParagonEx 10-09-2012 08:41 PM

Looks normal.

The flashing was most likely what the roofers had to work with because it was already there unless you paid them to replace it.

Roofmaster417 10-09-2012 10:21 PM

I have seen some of that black on roofs that were installed without felt.I see only one spot that looks a bit off color but I see nothing that leads me to believe they simply roofed over "Rotted" decking.

How was it determined that they roofed over rotted O.S.B ? How did you come to this conclusion ? Did you notice something within the attic on this section ?

The apron (flashing) could have been salvaged and had minimal damage had the roofers used a pry bar to loosen the fasteners over and under the apron instead of a tear off spade.That just bugs the heck outta me when people don't use pry bars when pulling step flashing from walls,skylights,chimneys and when cleaning aprons.

Roofmaster417 10-09-2012 10:58 PM


Grumpy 10-22-2012 02:04 PM

If it's OSB it should all be repalced :)

But seriously if it's stained, if it swollen, if it is soft, spongy, can;t hold a nail; it should be replaced. I prefer CDX as a roof sheathing, I see no benefit other than low price to using OSB.

The pics you are showing look ok for sheathing. There is a little bit of potential rott in the first pic bottom right hand corner.

AlleyG 10-23-2012 11:30 AM


Originally Posted by joecaption (Post 1027305)
I'm not seeing any rot in those pictures. The black just looks like old tar paper smuges.

The black holes rotted thru the OSB in the second pic dont bother you?


Grumpy 10-23-2012 12:41 PM


Originally Posted by AlleyG (Post 1036382)
The black holes rotted thru the OSB in the second pic dont bother you?


What holes? I double checked and even enlarged. I don't see any holes in either pic.

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