Thread: Weird spotting on roof sheathing

Can't remember seeing this before - but then saw it on two houses in two days. The OSB/PB roof sheathing showed extensive small blue-black dots. Not like any mold I have ever seen. Attics were in almost new, high end homes (sixty miles apart) with extensive soffit and ridge venting. The pattern of the spotting, with demarcations in the spotting between adjacent sections: extensive spotting up to the edge of the panel with none on the adjacent panel would indicate spotting or conditions that led to the spotting occurred before installation.
this may have been on a thread before. Anyone have an idea with this is?

I saw the something very similar to that in a brand new, high-end home as well. It was distinctly on the north side of the attic sheathing. The roof appeared to be vented properly with soffit grills and roof vents. The bathroom were not exhausting into the attic as far as i could tell either. Adequate amount of insulation was present was well.

I reported on what I could see and referred it to a specialist for further review. Any "experts" out there to give a definitive answer?

Thanks

Almost looks like the ink jet that prints the labeling had problems

Sorry for delay in responding to those who responded (something is not right as I know there are responses but I am unable to read them in this forum!).
Anyhow, I got feedback from a mold specialist shortly shortly after posting. The spotting is just 'ink spots' that are used to spray the product information on the roof sheathing. Maybe the sprayer went beserk that day. But these aren't mold-related. Very sloppy application, in any case. This was on Georgia Pacific roof sheathing produced in the last two years.

Originally Posted by Ernie Simpson

Sorry for delay in responding to those who responded (something is not right as I know there are responses but I am unable to read them in this forum!).
Anyhow, I got feedback from a mold specialist shortly shortly after posting. The spotting is just 'ink spots' that are used to spray the product information on the roof sheathing. Maybe the sprayer went beserk that day. But these aren't mold-related. Very sloppy application, in any case. This was on Georgia Pacific roof sheathing produced in the last two years.

Yep.... seen it many times. I was in a cont. ed class recently and the mold remediation specialist had a similar picture and showed everyone the difference between that and real mold. I guess he was sick of getting called out to "remediate" ink

I've just figured it happens when someone spills, drops or mishandles an ink cartridge when changing it at the factory. From a volume standpoint the amount of ink a plywood mill goes through is probably pretty large.