black mold

I have been remodeling our master bathroom and came to questionable area. I discovered black mold under our large atrium window. All the wood is fine but the concrete sheetrock stuff that was put on the house before it was bricked is crumbled. The damage was done before we replaced our roof in 2009. Sothis area is bone dry. The front window area is 7' wide by 8' high with side windows that are 4' wide by 8'high. I'm thinking I need to do something to the area where this concrete sheetrock area is crumbled before I insulate and sheetrock. Can someone tell me what needs to be done? I hate to cover up this and also feel like I need something as a barrier, so we don't have energy loss. The thought of having that whole area rebricked is making me worried but want to do the right thing. Thanks in advance for any suggestions.

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    A good general contractor needs to get eyes on that. My gut is that your windows were detailed poorly and that's caused all the leaking. You might be able to remove the windows/ rebuild the wall/ waterproof/ and replace the same windows. That said, thermal windows usually fail around the 20 year mark, so you might think about new windows if the existing ones are getting on in age. For now, encapsulate that mold. Commented Feb 12, 2022 at 21:33
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    A few more pictures after you clean up the area and remove the old insulation might help us answer better.
    – JACK
    Commented Feb 12, 2022 at 21:47
  • Since it is a bathroom, I would hazard a guess the damage came from water condensation on the interior of the window. If you see condensation in the future, run the fan! BTW: You should be able to lift that vent cover off and protect the opening with a rag. Commented Feb 13, 2022 at 14:34

1 Answer 1


You definitely have some mold but is it the bad stuff? I would remove the old fiberglass insulation and spray the area with 5% hydrogen peroxide. I usually suggest 3% but it looks like that is on the shade side so natural condensation will collect if there is air movement. If the wood is sound I would suggest filling those voids with a closed cell foam, more expensive than fiberglass and probably cheaper to have done but the problem won’t be back as closed cell stops any air movement. After that put in new sheetrock.

If you don’t want the expense of the closed cell foam get some new fiberglass and make sure it fits tight for no air movement and it should be fine for a long time.

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