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Community and Q&A

Attached garage issue

green654 | Posted in General Questions on


we built a house a year ago. I noticed a small amount of peeling paint around the baseboard in our front room. It’s probably about five inches long along  one section in of the baseboard. On the other side of this wall is the garage.  I noticed that there is a small gap at the bottom of the garage wall  in between the concrete floor and the drywall. Could that small gap be allowing humidity and thus condensation to form causing peeling paint on the other side of the wall which is the interior of the house?

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  1. Expert Member
    DCcontrarian | | #1

    You don't say what climate you're in, but are you in a cold place? Oftentimes you see that in a cold climate where there's a spot in the wall that isn't insulated. In the winter the spot is cold, the interior air is humid enough to cause condensation and you get moisture damage.

    A lot of builders have trouble with places like the spot where a garage attaches to the house. The exterior of the house should have a continuous layer of insulation, the garage should either be inside or outside that layer. If it's outside there needs to be insulation between the garage and the house.

    1. green654 | | #4

      We are in Chicago so cold winter, hot summer. Should we open up the wall to see if there is mold where the peeling paint is?

  2. Expert Member


    Insulation issue aside, you really want that wall to be completely air-sealed to stop contaminants from entering the house.

    1. green654 | | #3

      How do we completely seal it? There is a 1 centimeter gap around the entire perimeter of the garage wheee the floor meets the bottom of the wall.

      1. Expert Member
        BILL WICHERS | | #5

        If the gap is only between the drywall and the slab, that might not be a problem -- the drywall is typically sealed to the sill plate, and the sill plate sealed to the slab (or sealed with a gasket). If you have those two seals in place, then you should be good. If you're concerned, this sounds like a job for a can of Great Stuff.


  3. Expert Member
    DCcontrarian | | #6

    I think you're on the wrong track thinking that moisture is coming from the garage. Moisture generally moves from warm to cool. All other things being equal, the inhabited parts of a house have the highest moisture content -- each inhabitant contributes over half a gallon of moisture to the atmosphere each day. Unheated spots may feel damper, but they actually have lower moisture content than the heated areas.

    1. green654 | | #7

      We keep our winter indoor humidity between 20-30%. Summer between 40-50%. We have a whole house dehumidifier on each HVAC and an ERV. We are super conscious of our indoor humidity. What’s the best way to insulate a wall between conditioned living space and unconditioned garage wall?

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