Mold ?

This condo is 14 years old. My opinion is that this discoloration is old mold stains. Moisture meter shows dry. My theory is that the roof framing was wet when erected and the insulation and vapour barrier were installed before the wood had a chance to dry causing the formation of the mold or mildue. Any thoughts are welcome

I don’t believe it to be mold.Though I can’t say for sure without seeing it. The insulation acts as a filter & shows “soil filtration lines”. Basicly dirty air passing through the insulation.


Looks like insulation against the roof sheathing. Is it? If so, I rarely see it and always point that out as a bad idea. Traps heat against the sheathing, shortens shingle life, makes leaks difficult to find, etc. Could it be that’s a roof leak?

Could have been that the insolation got wet before it was installed , could be mold could be a stain of some sort,

Looks to me like water ran down that rafter. The staining is concentrated around it.


I would have breached this plastic…

You shouldn’t have a vapor barrier in the attic in the first place. The last time I ran into a similar situation, I breached the plastic and there was Mold on the entire roof sheathing area. Not good.

Everyone should go back and look at Post #2. Good call, DPlummer. Do you have a background in retrofit insulation and airsealing?

Why do you say this?

The vapour barrier can be sealed to act as an air barrier which should eliminate the condensation (if the moisture source for the mould to grow was not from rain leakage, etc) that has encouraged the mould growth!!

Plus the airsealing saves energy.

Usually if its a leaking roof you would see puddling in the drooping area of vapor barrier which is where the water would end up and I don’t see any of that in your picture as well as the 2x4 doesn’t seem to have soaked or stained? I’d go with the air infultration which I’ve seen before. Also agree with others about being a bad idea to put insulation right against sheeting!

Instead of explaining my stance on vapor barriers in homes, all over again…

See this thread

Participated in that thread with 4-5 posts.

In the above situation, how do you propose to stop air leakage and vapour diffusion through the fiberglass batts thus preventing moisture from contacting the cold roof sheathing causing condensation/mould/rot?

Brain, Thanks! 25 plus years as a restoration/remediation contractor I’ve crawled through a few attics.


the last house I inspected had similar stains and we decided they were caused by raccoon urine. just throwing that out there