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Thread: Sheathing

  1. #1
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    Default Sheathing

    Has any body seen this? It is inside the attic. Some kind of residue on the sheathing.

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  2. #2
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    Default Re: Sheathing

    That could be a mould growth. It seems to be following along the dark line at the rafter as well. Hard to tell. Could it be blown-in insulation? Frost?

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  3. #3
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    Default Re: Sheathing

    I would suspect mold growth - though it doesn't appear to be particularly widespread. Does it show on the other side of the rafter? Could be the sheathing was installed wet, or got wet before any roofing membrane was installed. Any moisture may have been trapped and perhaps drawn inside. Of course there could also be an active leak somewhere. How old is the roofing system?


  4. #4
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    Default Re: Sheathing

    Quote Originally Posted by John Kogel View Post
    That could be a mould growth. It seems to be following along the dark line at the rafter as well. Hard to tell. Could it be blown-in insulation? Frost?
    It is 50f in New Jersey and it's not blown in insulation. It's powdery and brushes right off. Could this be from an old leak? I tested the wood and it was all dry.


  5. #5
    Ted Williams's Avatar
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    Default Re: Sheathing

    Quote Originally Posted by Martin Muth View Post
    It is 50f in New Jersey and it's not blown in insulation. It's powdery and brushes right off. Could this be from an old leak? I tested the wood and it was all dry.
    This seems right to me, though maybe not from a leak. It could've just been bad storage at warehouse or on site. The way the sheathing is all furry it looks like it may have been extremely wet once, allowing the beginning mold growth, then quickly dried out after installation, killing the mold.

    Of course, I could be wrong.


  6. #6
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    Default Re: Sheathing

    Quote Originally Posted by John Kogel View Post
    That could be a mould growth. It seems to be following along the dark line at the rafter as well. Hard to tell. Could it be blown-in insulation? Frost?
    Quote Originally Posted by Ian Page View Post
    I would suspect mold growth - though it doesn't appear to be particularly widespread. Does it show on the other side of the rafter? Could be the sheathing was installed wet, or got wet before any roofing membrane was installed. Any moisture may have been trapped and perhaps drawn inside. Of course there could also be an active leak somewhere. How old is the roofing system?
    Quote Originally Posted by Ted Williams View Post
    This seems right to me, though maybe not from a leak. It could've just been bad storage at warehouse or on site. The way the sheathing is all furry it looks like it may have been extremely wet once, allowing the beginning mold growth, then quickly dried out after installation, killing the mold.

    Of course, I could be wrong.

    This is a townhouse built in 1987.


  7. #7

    Default Re: Sheathing

    Maybe FRT plywood?

    Is the sheathing delaminated at all, and is it original?
    Reason I ask is that I don't see moisture stains around the exposed nails, nor do I see much in the way of corrosion on the nails, which leads me to rule out the mold idea, but it's tough to tell from the pictures.


  8. #8
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    Default Re: Sheathing

    It certainly seems to be fungal / mold growth to me which looks newer than the 1987 date. Perhaps the roof leaked elswhere than above that particular unit and migrated to the area now observed. Were you able to physically check the integrity of the roof itself? Any signs of repair or existing defect?


  9. #9
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    Default Re: Sheathing

    Quote Originally Posted by Brandon Whitmore View Post
    Maybe FRT plywood?

    Is the sheathing delaminated at all, and is it original?
    Reason I ask is that I don't see moisture stains around the exposed nails, nor do I see much in the way of corrosion on the nails, which leads me to rule out the mold idea, but it's tough to tell from the pictures.

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  10. #10
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    Default Re: Sheathing

    Quote Originally Posted by Martin Muth View Post
    This is a townhouse built in 1987.
    I'm guessing you're seeing some evidence of past or present gypsum board or layer plus moisture and heat non-"exposure" side.

    What's on the other side of this plywood, exactly, layers (note minimal nail penetration). Proximity to common wall, parapet, etc. what is where?

    Suspect fire rated assembly.


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