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Building wood stain

user-6651407 | Posted in General Questions on

Can anyone help explain what would cause a stain like his. It’s on treated wood. Almost like a chalk stain, but does not rub off. I have a few pieces like this.

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  1. GBA Editor
    Martin Holladay | | #1

    The photo is far from clear. What are we looking at? Does the photo include a slab? Other materials? Please describe the photo better.

  2. user-6651407 | | #2

    Concrete floor, treated wood, then OSB. The treated wood with the stain is in the center. I will try to get a better pic.

  3. user-6651407 | | #3

    This is another photo. This is just one piece that has the stain. I have some other cut pieces, just extra, with the same stain. Almost wondering if something that cut the wood left it behind.

  4. GBA Editor
    Martin Holladay | | #4

    Looks like good old fashioned mold to me. If the area is now dry, and unlikely to get wet again, the presence of mold is usually not a problem.

    Did the builder install sill seal between the concrete slab and the plate?

  5. user-6651407 | | #5

    I am unable to tell if there is a sill seal. Would you recommend any steps moving forward? Would this be able to be remedied, if no seal present? Also, do you recommend sending off a sample to a lab for testing? I measured with my moisture meter and it’s at 0%

  6. GBA Editor
    Martin Holladay | | #6

    If you are getting a reading of 0% moisture, you must not be using your moisture meter correctly. The moisture content of the wood has to be higher than 0%.

    There is nothing to be gained from sending a sample to a lab for testing.

    You should poke the 2x4 with an awl to see if it is firm or punky. If it is punky, you have a rot problem. If it is firm, there is probably no need to worry.

    If you want, you can drill a 1-inch hole in the middle of the plate with a cheap spade bit. This effort will ruin the bit, but spade bits are cheap. When the spade bit hits the concrete, finish cutting the hole with a sharp knife, making a circular motion at the perimeter of the hole. Once the hole is cleaned out, you should be able to tell if there is any sill seal between the 2x4 and the concrete.

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