How to Solve Moisture Problems Under Your Home

By: Danny Lipford

We live in an older home that is raised a couple of feet off the ground with a crawlspace under it. In the past few years, the hardwood flooring in several rooms has started to warp and cup. What could be the problem?-Mary

Hi Mary,

It sounds like you may have excessive moisture and humidity in the crawlspace under your home. Here’s what you can do to correct it:

  • Make sure the ground around your foundation slopes away from the house (1/2″ per foot or more).
  • Divert rainwater run-off from the roof away from the foundation by installing gutters and extending the downspouts so water is diverted beyond the planting beds and out into the yard.
  • Check your air conditioner unit to be sure the AC drain pipe isn’t clogged and extend it if needed to direct condensation water away from the foundation of your home.
  • Inspect the crawlspace under your home. While the soil may be moist, it shouldn’t be saturated or have standing water.
  • Look for any plumbing leaks as well as excessive dampness, mold, and mildew.
  • If mold or mildew are present on the joists or bottom of the subfloor, treat under the house with a product such as Concrobium Mold Control (available at The Home Depot along with a fogger to rent).
  • Clean out any debris and stored items under your house, and fill in any holes or depressions.
  • Cover the entire crawlspace with thick, black plastic sheeting (6 mil or higher). Overlap the seams by a foot or more and run the plastic up the sides of the foundation.
  • For extreme moisture problems, consider taping the seams in the plastic together, block the outside vents, and install a dehumidifier in the crawlspace to remove excess moisture from the air.

Good luck with your project,


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18 Comments on “How to Solve Moisture Problems Under Your Home”

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  • Clarence Mills Says:
    September 7th, 2017 at 8:08 pm

    What kind of monitor do I need to put one part under my crawl space
    and one part in my house .Do I need a monitor for humidity,moisture
    or what to let me know whats going on under my crawl space. One
    person told me i needed a moisture meter and the moisture contents
    should not be over 16%. Another man said I needed humidity monitor.

    Need Help
    Clarence Mills

  • Charles Brewer Says:
    December 5th, 2016 at 9:28 am

    My house was built on top of a concrete slab above it with piers. A crawl space of 26″ the plywood has rotten through in one room there. Is brown mold present under most of the house mostly the middle. Need to know how to prevent the rest of the house from rotting and I had never insulated the floor.

  • craig Says:
    October 6th, 2016 at 12:24 pm

    I have 4ft + of crawl space live in Florida and have bad rainy summer. Crawl fills with water and now subfloor is rotting and worried man made floor joists are also moldy tried to swayl yard but water stays for awile as yard is flat

  • Meagan Mangold Says:
    September 7th, 2016 at 1:08 pm

    Do you think moisture barriers under the house are a good or bad thing or does it depend on certain factors? I have heard mixed opinion as to whether they actually draw and attract a moisture problem as opposed to prevent it.

  • David Headley Says:
    July 19th, 2016 at 2:21 pm

    i have two vent fans planed in foundation to remove moisture from under home. what percent of humidity do i need to achieve. i have humidistat set on 55%.

  • Leslie Nuckolls Says:
    February 23rd, 2016 at 9:01 am

    We have a moisture problem in our foundation. This is a newly constructed home and they applied a moisture barrier when the foundation was poured. We did the acid stain floors and it started turning milky and bubbling. That is when we found the moisture problem. We did the test and it came out with a 13.2 and13.6 moisture. We were told that this is excessive. Is there a way to correct this?

  • Marcy Lucas Says:
    January 24th, 2016 at 7:51 am

    I think i have a moisture problem under my crawl space I went into my closet to get a pair of shoes and found that mildew or mold is growing all over them I searched closet for moisture leaks ect nothing …..who am i to call in a situation like this I need help….1st time home buyer

  • Marcus Says:
    January 13th, 2016 at 2:57 am


    I’ve had a tree next to the house removed and now the house is cracking and doors jamming. Understand it could be moisture returning to the soil. What can I do to dry up the soil under the house? Since I can’t unremove that tree now!!

  • Dianne Says:
    January 1st, 2016 at 12:49 pm

    My floors pop real bad and you can hear it run across into other rooms and my carpet is starting roll up in my bedrooms. I do not have mold or mildew under my house. Will moisture cause this or do I have a bigger problem?

  • Diane Drennan Says:
    December 25th, 2015 at 12:13 am

    Can you tell me what kind of business you call to divert rainwater and slope the ground away from the house? I have excessive moisture in a ranch with a slab.

  • Crystal Says:
    December 15th, 2015 at 5:18 pm

    My father in laws house has lots of moisture and I think mold. He is fighting cancer and want to know who I can call locally to come check the air quality in his home?

  • Lewis Says:
    December 14th, 2015 at 12:50 pm

    Hi Danny,

    Thanks for the great advice!

    Any tips for someone who has a house that’s on a steepish hill, as it’s not very practical to make a slope away from foundations 🙁

  • INBA Says:
    December 11th, 2015 at 4:01 am

    One effective way to combat moisture is by the use of desiccants like Silica Gel. We have some moisture barriers in the house to absorb some of the moisture. I can smell a musty smell and am having bronchial infections now.

  • Teshine Good Says:
    April 20th, 2015 at 8:12 pm

    We have an old family home that is built very close to the ground. Occasionally, mold appears in different places inside the house. When it rains a lot, the house smells and feels damp. We have some moisture barriers in the house to absorb some of the moisture. What can we do to eliminate/reduce the moisture in the house?

  • Leanna Says:
    March 21st, 2015 at 8:37 am

    We have a crawlspace under a small section of our home. Unfortunately, my sewing room, which I’m in a lot, is located just on the other side of the poured wall. I can smell a musty smell and am having bronchial infections now. We have put a thick layer of black plastic over the ground several years ago, but still can smell something, and I’m still having bronchial infections when I sew very much. HELP!

  • MIKE H. Says:
    July 30th, 2014 at 3:42 pm


  • Gail Butler Says:
    July 30th, 2012 at 7:22 am

    I am having problems with excessive condensation under my home. It is causing mold/mildew underneath my house. The insulation is all wet (I have had this removed). Some of my floors are now bulkling/swelling and in one room, the sheet rock is wet. I have had 2 air-conditioning repairmen come to check my AC unit and they are unable to find anything. I have had a contractor come & check for any leaks, pipes or roof leaks and none are visible. Insurance adjuster has come and says this is condensation but no one is able to find out where it is coming from. This has all happened or at least shown up in the last 2 months. I had renovations done 2 months ago and none of this was present then and it was dry underneath my home. Even though I am planning on getting treatment for the mold and getting new insulation, I still do not know where the problem is. How can I find out-who do I contact for this? I have also asked for a home inspector to come but they don’t handle this type of problem either from what they tell me. I am desperate to find a solution. My house seems to be deteriorating and there isn’t anything I can do to prevent it. Please help.

  • Sasha Says:
    October 7th, 2010 at 2:09 am

    One effective way to combat moisture is by the use of desiccants like Silica Gel. These are the same small sachets you find in packaging of various products like electronics, garments, etc. Silica Gel works by absorbing the moisture in its surrounding area. For most moisture challenges, does the job. With small sachets cost less than a dollar, it truly is a cost effective way of protection from moisture.

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How to Solve Moisture Problems Under Your Home