Mold? Attic Decking

[Mike agnello]

The 2 bays closest to the south side of the house have discolored decking about 3' high from the roof edge.
The roof faces west, there is tree cover but the roof should get plenty of sun.
We are in Michigan.
I don't know what else would cause the discoloration or if this would be toxic black mold. It seems more stained than growth on top of wood.

There is a ridge vent along top but little to know circulation in attic.No top hat vents for this area of attic. Bungalow w finished upstairs, the kneewalls are insulated, and no baffles to allow air flow to upper part of roof.
There are no vents exhausting into this area of attic.

[Eric Barker]

With the 1X decking boards I'd guess that this is an older home. No way to know what conditions or venting provisions have existed over the years. Also, just because baffles are absent doesn't mean there is no air flow from the soffits.

If this is all you saw I wouldn't get too excited. Comment on the presence of the staining and if desired make a remark that its cause was not determined. Going the "get a mitigator" route would be a bit extreme. And stay away from the toxic mold references - you'll only send people into a needless hyperdrive panic.