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Do You Need A Moisture Barrier For Your Crawl Space?

Do You Need A Moisture Barrier For Your Crawl Space?
Do You Need A Moisture Barrier For Your Crawl Space?

Thinking about a moisture barrier for your crawl space?

If so, you’re on the right track. An uncovered dirt floor in a crawl space allows water vapor to enter the area and cause serious problems, including mold, wood rot, and structural damage.

This article will go over what a moisture barrier for a crawl space is, the difference between a crawl space moisture barrier and encapsulation, why moisture is bad for a crawl space, and more.

What Is A Moisture Barrier For A Crawl Space?

A moisture barrier for a crawl space is a thick plastic sheet covering the crawl space floor. A moisture barrier’s purpose is to prevent water vapor in the soil from entering the crawl space. A crawl space moisture barrier only covers the dirt floor of the crawl space, not the walls.

While a moisture barrier for a crawl space doesn’t completely stop water vapor in the soil from entering the crawl space, it does slow it down. Of course, a moisture barrier for a crawl space only helps keep out water vapor in the soil. It doesn’t do anything to prevent liquid moisture from entering the crawl space via a high water table, excess moisture in the soil around the foundation, or leaky plumbing.

What’s The Difference Between A Moisture Barrier And Encapsulation?

A moisture barrier just covers the crawl space’s dirt floor. Crawl space encapsulation covers the floor and the walls, isolating the dirt floor from the rest of the crawl space. During encapsulation, all open vents are sealed off as well. We recommend adding a dehumidifier and a drain tile system along with encapsulation. For more information, see Don’t Install A Crawl Space Dehumidifier Without Encapsulation.

Why Moisture Is Bad For A Crawl Space

Moisture in a crawl space can lead to serious structural issues for the home and respiratory problems for the home’s residents. Here’s why…

Crawl space moisture can lead to wood rot and decay. Given that the wooden structures in the crawl space literally hold up your home, this can weaken the house’s structural integrity.

Moisture in the crawl space also fosters mold growth. This is a serious problem because some of the crawl space air flows into the home’s living area via the stack effect. If the air in the crawl space is full of mold, the air in your home will also contain mold spores. This could trigger allergies or respiratory problems for anyone living in the house.

A dark, damp crawl space also attracts wood-eating pests like termites and rodents with dangerous droppings. Snakes and other creepy crawlies are also known to seek shelter inside crawl spaces. This is one reason we strongly recommend homeowners leave crawl space repair and waterproofing to the pros.

the stack effect Epp Foundation Repair

What Are The Benefits Of Encapsulating A Crawl Space?

The benefits of encapsulating your home’s crawl space include the following:

  • Improved air quality in your home – A clean, dry, mold-free crawl space means the air flowing into your home will also be mold-free.
  • Lower maintenance costs – If your crawl space is dry, clean, and mold-free, there’s far less chance of structural damage from things like wood rot, termites, and rodents.
  • You gain valuable storage space – While we don’t recommend storing valuables in an encapsulated crawl space, you can use the encapsulated area to keep things like tools, holiday decorations, canned food, etc.
  • You might save money – We don’t guarantee you’ll save money on heating and cooling costs. However, some customers have reported lower energy bills after encapsulating their home’s crawl space. This is probably because a dry crawl space under the house means lower humidity inside the home. The lower the humidity inside the home, the easier it will be to heat and cool.

Read more – How To Clean Up A Crawl Space

Other Ways To Prevent Moisture In A Crawl Space

The best way to prevent moisture in a crawl space is to control groundwater around the foundation. In other words, your goal should be preventing excess moisture from building up in the soil. Here are a few ways to do that:

  • If your yard slopes toward your foundation, regrade it so that it slopes away from the foundation – You don’t want water draining toward the house and pooling in the soil around the foundation. That’s a great way to end up with a wet crawl space!
  • Make sure your gutters are debris-free – Clogged gutters can cause runoff to spill over the side of the house and soak into the soil around the foundation.
  • Keep flowers, shrubs, trees, etc. away from the foundation – You don’t want a reason to add water to the soil around the foundation.
  • Install downspout extensions so that runoff gets channeled away from the foundation before being released.
  • Install an underground downspout along with a pop-up emitter – Runoff flows into the underground downspout toward the pop-up emitter situated somewhere in your lawn, usually about 10 feet away from the foundation. When it’s empty, the pop-up emitter sits flush with the ground and is barely visible. When it fills with water, it pops up and releases the water away from the foundation.
    Install a drain tile system – Nothing beats a drain tile system for controlling groundwater around a foundation. For information on how they work, see How Does A Drain Tile System Work?

If you’re thinking about a moisture barrier for a crawl space and you’re in our service area – Nebraska, Iowa, Kansas, and Missouri – contact us today and we’ll come out for an evaluation and then offer you a cost estimate.


Dave Epp

Dave is the President at Epp Foundation Repair with over 27 years of experience in the industry. Dave has worked on thousands of foundation, basement, concrete, and crawl space repair projects since 1993. Dave is involved in several civic and church organizations and enjoys coaching youth sports, mainly football, golfing, and elk hunting.



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