Mold?

Well, *it is* "fungi".

And "mold" is "fungi".

But I would not want to go start chasing that "mold" dog down.

That "fungi" (it is a "fungus") is likely damaging the wood, did you jab your screw drive into the wood?

If the wood is soft and damaged, then it is a 'structural' problem/

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )