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  1. #1
    Join Date
    Jun 2009
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    5

    Unhappy Floor Joist issue - Dehumidifier making basement too dry?

    I posted this in the Basement section, but just realized my question may be more relevant for this section. Sorry for the double post.

    I bought a second dehumidifier several month ago for my basement because 1 was not enough to maintain the humidity for the entire basement. I've had the humidifiers set on "continuous" for several months (rather than a set humidity), but was wondering if that might cause issues with the air being too dry. In other words, will the floor joists or subfloor on the first floor (basement ceiling) shrink and/or crack if they are too dry? I just started noticing in the morning when I get up the floor creaks a lot more, but after walking on the floor for a while, it doesn't creak anymore. Is this because the wood shrinks when the air is less humid? The house was built in the early 50's and has pine floor joists with tongue-and-groove boards for the subfloor. I live in New England so the humidity level changes throughout the year.

    Thank you in advance for your help.
    Last edited by oldhouse8; 06-06-2009 at 04:20 PM. Reason: made title more specific

  2. #2
    Join Date
    Jun 2009
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    5

    Default Re: Dehumidifier making basement too dry?

    Can anyone help me

  3. #3
    Join Date
    Apr 2008
    Posts
    74

    Default Re: Dehumidifier making basement too dry?

    I live in New England as well and know what you mean about humidity variation. Between the very dry winters and the humid summers, our house goes through the swelling / dry-out cycles several times per year.

    All that being said, I don't think you can ever have too dry of a basement this time of year. The dryer you keep it, the less chance of mold build-up, and the less chance of having allergic reactions to any spores in the air.

    I wouldn't be too concerned about squeaky floors. If it's a choice between the floors squeaking and keeping the basement dry, I'd go for a dry basement.

    You could try setting your dehumidifiers on a set humidity level and see if that works to keep you dry and the floors quiet. I run mine on 40% - 45%. That's plenty dry and no wood shrinkage issues. Can't hurt to give it a go!

    Good luck. Tim

  4. #4
    Join Date
    Jun 2009
    Posts
    5

    Unhappy Floor Joist issue - Dehumidifier making basement too dry?

    Thanks for your reply, Tim. I just checked the humidity level in my basement with an Indoor/Outdoor Thermo-Hygrometer and compared it to what my new humidifier said and discovered that the humidifier says the humidity is 25-30% higher. So essentially if I thought my basement was at 40% humidity, it was actually closer to 10-15% humidity. Ugh!

    That said, I assume I decreased the humidity level so much in my basement that it was enough to shrink the floor joists and/or subfloor. Do you think that is correct? The weird thing is that when I walk on the floor in the morning, it is not only the floor that creaks, the nearby wall creaks too, but then stops after a while. It seems that as I'm walking, the floor and the nearby wall settles. Is this because the wall is nailed to the floor and if the floor moves slightly, the wall is pulled with it?

    I hope I'm making sense. It is just weird this all of a sudden started happening. I've lived in this house for several years and never experienced this. The only thing I can think of is that adding the humidifier is causing this. Thoughts?

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