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Community and Q&A

Mold on lumber

Rocky12 | Posted in General Questions on

Hello there,

I have noticed some black spots on my lumber, that seem to be from spilled pain perhaps, but looks like some mold has grown over top.

For those of you who care enough about mold, what works well cleaning it off? I was thinking of using a mold cleaner then sanding.

If I do that, how long do you think I should give it before I start sheathing and closing the walls in?

Here are a few pics

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  1. GBA Editor
    Martin Holladay | | #1

    That type of mold on framing lumber has been common for as long as we've been building stick-built houses -- for at least 150 years. I wouldn't worry about it (unless you have someone in your house with a special medical condition).

    Once the house is dried in, there won't be enough moisture near the studs for the mold to grow.

    If you want to try to remove the mold, ordinary dish detergent and water (along with a brush) is all you need. Don't attempt this work until the house is dried in, and remember to clean up your puddles.

    Once again, I think that trying to remove this mold is unnecessary.

  2. Rocky12 | | #2

    Hi Martin

    Thank you for your response. Actually we do have someone in the family with a medical condition.

    I was looking at a product called mold armor. I take it you have never used it ?

    Why do you say to wait to remove the mold until after the house is dried in ? Wouldn't it make sense to do it now when the studs are free and have airflow to dry ?

  3. GBA Editor
    Martin Holladay | | #3

    Until you have a roof and windows, you've got rain. Studs that are rained on are much more likely to have mold than lumber that is indoors.

    You need to have a dry environment to get rid of the mold.

  4. Rocky12 | | #4

    True. Better not to chance it. How long should I wait to put the insulation and interior walls in after cleaning the framing with mold cleaner ?

  5. Expert Member

    if you use an encapsulating treatment like Concrobium you could insulate that day.

  6. Expert Member
    Dana Dorsett | | #6

    It's best to wait to insulate until the moisture content measures under 20%, spot checking multiple areas with a 2-pin wood moisture content meter.

    If it's taking too long to get there putting you in a calendar time crunch, insulating when it's under 25% is fine as long as you don't paint the wallboard right away, and are heating or dehumdifying the place 24/7.

  7. Rocky12 | | #7

    Hey Dana, thanks for the reply. I'm going to use Mold Armor
    32 oz. Mold Remover and Disinfectant Pro-Strength

    What do you think?

    It's quite warm outside so I figure I will give it 3-5 days to dry before sheathing.

    I'm also planning to sand down afterwards if anything is left.

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