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Crawlspace Moisture Problems

| Posted in General Discussion on December 3, 2002 04:49am

    The crawlspace in a house I am working on has a moisture problem that I am at a loss to fix.  maybe someone out there can help.  The house is new construction and is insulated with corbond, however there is no insulation between the crawlsace and the first floor.  The crawlspace is unheated, but does contain an electric hot water heater and associated hot and cold water pipes.  The heating plant is a Rinnai, direct vent LP space heater on the main living floor. The floor of the crawlspace is a concrete/vermiculite mix sold under the trade name nuetocrete and, in theory, acts as a vapor barrier.  Finally, there is no access to the crawlspace from within the house, you must enter through an outside steel door.

    The problem is that the humidity is a constant 80% and anything in the crawlspace mildews quickly.  Also, in winter months, the interior portion of the foundation that is above grade forms condensation as does the insulated steel door to the outside entrance.

    It seems to me that anything done to ventilate the space is going to cause pipes to freeze and other bad things. Any ideas? 

 

 

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  1. Piffin | Dec 03, 2002 05:11am | #1

    Install a dehumidifier and find the source of the water. I'm not familiar with the ground cover you have but it sounds like it should have had a plastic type VB put down first.

    Are the foundation walls waterproofed and insulated?

    .

    Excellence is its own reward!

    "The first rule is to keep an untroubled spirit.

    The second is to look things in the face and know them for what they are."

    --Marcus Aurelius

    1. dlwaterman | Dec 03, 2002 06:07am | #3

      Can't find any other source of water than the condensation running off the walls and occassional water up through the only portion of the floor that did not get the Nuetocrete treatment (approx. 12 X 15). this part of the floor just has a thin concrete slab.  There is a poly vapor barrier under the Nuetocrete.  Also, the foundation was waterproofed (tarred) but is not insulated either inside or out. Finally, there is no dehumidifier operating currently since the temp. is below 60 degrees in the crawlspace.  Thanks in advance for any additional info.

  2. luvmuskoka | Dec 03, 2002 05:37am | #2

    I built my present home on a crawl space (high water table). It's unheated, well vented, and my floors are insulated. I used 2 layers of heavy black plastic on the floor. It's always very dry.

    Is this crawl space vented properly? I hope there aren't any hardwood floors above, I can imagine the crowning/cupping taking place.

    Ditch

    1. dlwaterman | Dec 03, 2002 06:13am | #4

      This house is also located in an area with a high water table. FYI, the crawlspace is not vented at all since it gets plenty cold in upstate New Hampshire and we have concerns about pipes freezing and energy costs.  The floors above are actually wide board eastern white pine and, to date do not show any signs of cupping or crowning.  Humidity in the living spaces is very low.

      1. luvmuskoka | Dec 03, 2002 06:22am | #5

        DL,

        I'm 45 mi. south of Erie, I'm sure it gets as cold here. I leave the vents open slightly in the winter . It was 45 degrees down there last winter when outside temp was 9 above. I think the floors should be insulated and vents installed.

        Have you checked moisture content in the sub-floor? If it's high it will eventually migrate to the finished flooring above.Ditch

      2. Piffin | Dec 03, 2002 06:24am | #6

        Tarpaper under those pine boards? That may be delaying the inevitable.

        A vent like radon ventilators use might be your solution..

        Excellence is its own reward!

        "The first rule is to keep an untroubled spirit.

        The second is to look things in the face and know them for what they are."

        --Marcus Aurelius

        1. suntoad | Dec 03, 2002 11:11am | #7

          I'm in S.Central Alaska.  Nearly all houses are built over (insulated) crawl spaces here.  Code is to have open vents on opposing sides of the crawl space for constant through-ventilation.  It works, and so long as no pipes are directly in front of the vents, generally nothing freezes.  When it gets real cold (20-40 below), some people close their vents.   Never a moisture problem (unless some fool has vented their dryer into the crawl space!).

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