Thread: Sheathing

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

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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?

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?

Originally Posted by John Kogel

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.

Originally Posted by Martin Muth

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.

Originally Posted by John Kogel

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?

Originally Posted by Ian Page

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?

Originally Posted by Ted Williams

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.

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.

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?

Originally Posted by Brandon Whitmore

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.

POSITIVE

Originally Posted by Martin Muth

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.