Protect Your Home Against Crawl Space Moisture

floor rotted from moist crawlspace
Floor Rot from Crawl Space Moisture

Moisture in your crawl space is bad. Not only will it cause direct and costly damage to the foundation and framing of your home, but crawl space moisture can also lead to growth of mold and mildew that causes health problems.

Your first line of defense against is detection. Unfortunately crawl space wetness often goes undetected until damage occurs because home owners don’t like to get in there; crawl spaces are usually dark, tight spaces with dirt floors, bugs and webs. However, if the home owner doesn’t crawl in there and inspect the space at least once a year (preferably three times a year at seasonal changes and after heavy rains), he or she should be arranging for someone to inspect the crawl space for moisture and any new structural issues such as significant new cracks in the foundation or in the floor joists of the flooring above the crawl space.

excavated crawlspace
Excavated Crawl Space for Flooring Repair

Most of the time, you or your inspector will find little to no moisture, and any required moisture-prevention is pretty simple. In any cases, from little to heavy moisture, all moisture prevention solutions cost less than the consequences in terms of structural damage or health issues.

So, you get yourself in there, and what are you looking for?

5 Common Sources of Moisture

If you are doing the inspection, you are primarily looking for moisture and the source of it. There are five main sources of moisture in your crawl space:

  1. Crawl space ground moisture
    Most crawl spaces have dirt floors, and unless you live in the desert, some degree of moisture will be coming up through the dirt, trying to evaporate to the outside. When it’s warmer, evaporation is faster. If that moisture just hangs in the stale crawl space air instead of being blocked with a vapor barrier (plastic encapsulation of the floor and up the walls) and/or with ventilation to exhaust the moisture to the outside, that stagnant moisture will crack the foundation, rot the floors above, and create a growth environment for mold and mildew.

    Crawl space ground/dirt moisture can be significant or not, depending on where you are, i.e., in or near a flood zone? This varies widely across the Louisville area, being in the Ohio River Valley and with neighborhoods ranging from flood zones to hill crests. A good time to simply check for moisture in the dirt floor of the crawl space is after a heavy rain, and after the Spring rain season.
  2. Ground water seeping or leaking in from outside of your crawlspace
    It’s easy to tell if this is the case. The crawl space dirt floor is wetter around wall or walls where the ground water is seeping in, and you can see the water outside, pooling against the foundation where the crawl space is. This is usually caused by not using downspout extensions and grading the ground around the foundation to drain the water away.
  3. Gaps or cracks around the crawl space doors
    If there are gaps around your crawl space doors, whether or not you see or feel moisture there, seal them up by wrapping the inside of the door in plastic and using some type of sealing or insulation material from the hardware store to fill the gaps.
  4. Crawl space vents
    A lot of old crawl space vents can be more of a problem than a help. If left open and not being used with an encapsulation system to exhaust moisture with a fan system, the open vents can allow moisture in. The old vents, meant for cross-flow of air in the crawl space, are usually too small for the intended purpose. They should be checked by a crawl space expert to see if they are helping or hurting any crawl space moisture issues.
  5. Leaks from appliances above or within the crawl space
    That slow drip from the back of the refrigerator is going somewhere … the crawl space below. If you don’t regularly visit the crawl space, you might not know about the leak until you notice your floors starting to bounce, feeling “squishy” and sounding “squeaky.” At that point, the damage to the floor joists is probably done. Instead, if you catch the leak from inspecting the crawl space, it’s a simple fix of the refrigerator leak.

    Likewise if your leaks are from within the crawl space. If you have a water heater or plumbing in the crawl space, little pin-hole leaks could be sources of significant moisture. Detection would require inspecting all areas around the tanks and pipes for moisture in the concrete or dirt floor of the crawl space.

And Then What? Crawl Space Moisture Solutions.

encapsulated crawlspace
Encapsulated Crawl Space with Floor and Walls Wrapped in Plastic

If there is enough moisture in the crawl space to cause damage or health issues from mold and mildew, the required solution depends on the source of the moisture. These are the most typical crawl space moisture solutions:

  1. If moisture is coming from the crawl space floor and gaps.
    Excavating and wrapping/encapsulating the crawl space, to create room for working and moving in the space, to create a cleaner environment for easier detection of moisture, and to create a plastic vapor barrier across the floor and walls. This work also includes sealing of any gaps that aren’t serving an air-circulation purpose, such as vents or gaps around the crawl space doors.

    As needed, ventilating solutions can be added to ensure that the air circulates in your crawl space, and helps evaporated moist air get conditioned/de-humidified or exhausted to the outside.
  2. If moisture is coming from outside ground water.
    Usually a simple solution of downspout extensions and grading the soil around the foundation to move water toward a drain. A french drain or other yard drainage solutions may be needed to complete the drainage solution.
  3. If moisture is coming from appliance or plumbing leaks.
    This is very simply a detection and fix of the leak, but detection needs to come first with the regular inspection, and probably also with an excavating clean-up job to make moisture detection easier.

Once you make your crawl space a dry space, or confirm that it already is … take advantage of that space! It could be useful for storage, provided that you don’t cram it full of boxes from wall to wall, which would prevent future moisture detection. Also, whether your crawl space is dry or not, and even if it’s encapsulated and ventilated, only use plastic storage containers for storing items in your crawl space.

Request Your Free Crawl Space Inspection

Kentuckiana Home Services can perform an initial inspection of your crawl space at no cost, to report any evidence and sources of moisture, and to make recommendations for any solutions or methods of prevention. Contact Us for your free inspection and consultation.