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Are these signs of moisture in the rim joist area?

marks77 | Posted in General Questions on

Hello, I’m insulating my walkout basement and I noticed these dark spots on the corner of my rim joist, especially the bottom of it. Are these signs of moisture? This is above the walkout side, maybe 9ft above ground. No other area on the perimeter looks like this. Is this something to worry about? Thanks.


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  1. Expert Member
    BILL WICHERS | | #1

    It's possible that's moisture, but it could be sap staining. You might try gouging out some of the dark spots and see what is underneath. Sap will usually be crumbly and a little crystal like, similar to dark amber. Water damage won't be crystal-like, and if it's rot, it will be noticeably softer than the rest of the board.

    If the problem is localized to one spot, it's worth checking for any signs of water intrusion around that area just to be sure.


  2. marks77 | | #2

    Bill, I did what you said and you're right, this appears to be a very thin stain of some kind. It's brittle and there is good wood right underneath. Thank you for the suggestion and the advice!

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