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How to remove mold on sill plate of 2 x 6?

green654 | Posted in General Questions on

I have a family member who is EXTREMELY sensitive to mold and gets very sick from it. She started feeling sick so I poked around the house and found a suspicious area. We did testing and it showed mold so we went through remediation to try to remove the mold. Unfortunately, it is located on the sill plate of a 2×6. The remediator said he can’t remove it because it’s load bearing. But somehow I need to get the mold physically removed from the house to help my family member feel better. Any ideas?

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  1. Expert Member
    DCcontrarian | | #1

    Normally sills are insulated. I would encapsulate it in spray foam.

    1. green654 | | #2

      There was rock wool insulation. We had to remove it in the section above wheee tree mold is. Do you think it’s fine to insulate just that area with spray foam if the rest of the house is rock wool?

      1. Expert Member
        DCcontrarian | | #3

        That's probably the cause of the mold. If you have permeable insulation, humidity in the interior air can reach the cold side of the insulation and cause condensation, over time the condensation leads to mold. To prevent this the rim joist and sill should have a layer of spray foam. You can put the rock wool back after the foam.

        It's usually not a problem in walls because there's paper facing or some other vapor retarder on the interior face to keep humidity out of the wall.

  2. green654 | | #4

    The moisture was inside the wall cavity due to an issue with the venting of the hot water heater that has since been rectified. We have rockwool as the insulation throughout the house and a smart vapor retarder and we keep our winter humidity extremely low (low 20s) and we’ve had no moisture issues inside the walls. This specific issue was a one off situation. I just wish there was a way to cut out the sill and replace it with a clean piece of wood. Frustrating.

    1. Expert Member
      DCcontrarian | | #5

      In that case just wash the area with bleach and water, let it dry thoroughly, and seal it with a sealing primer like BIN.

      1. Expert Member
        BILL WICHERS | | #6

        I would actually recommend using one of the "mold killing primers" instead of BIN in this case. Zinsser makes such a primer that I've used in the past. The mold killing primers help to prevent the mold from coming back, BIN just encapsulates whatever may be left behind from the original mold.


  3. walta100 | | #7

    I agree with DC and Bill that cleaning and painting is a good solution for most people but this poster is not most people. My guess is so long as that moldy board remains in the house the poster is likely to blame every symptom they feel on its presence.

    The fact that it is under a load bearing wall does not mean it is impossible to replace. It does make it difficult and expensive to replace. This part of the job may well be beyond the mold remediation contractor’s skill set but a competent contractor could build the temporary walls to support the loads and replace the moldy board. Understand this is a can of worms in that under this board you are likely to find mold on the subfloor. Only the poster can decide if replacing the board would be $5000 to 10,000 well spent knowing insurance will not pay this cost.


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