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Encapsulating a crawl space is a common way to deal with moisture or flooding. It is also an easy way to quickly get control of the air quality in the home and lockout rodents and insects. When you’re thinking about “green-ovating” your home, or simply getting control of the moisture or humidity, when you have a crawl space, you must encapsulate.

Encapsulation does a great deal for the crawlspace and for the home above.

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What the process is and what it does

The practice of encapsulating or “sealing off” a crawlspace is done to lock out moisture and cut off the connection between moisture, water and the joists of a home. By running a vapor barrier down the walls of a crawl space to completely cover the floor, you essential separate the outside from the inside of the home.

This vapor barrier will be the flexible membrane between the walls and floor and the rest of the home. A properly designed vapor barrier will limit the transfer of moisture through it while regulating the speed at which air will naturally pass through. This helps to limit and control the amount of moisture that will find its way into the air space and completely segregate liquid water and direct it to a sump location.

mold in crawl space under house

5 helpful tips when having a Vapor Barrier installed in your crawlspace:

1.) Not all vapor barriers are made for this task – careful. There are many products out in the world that claim to be able to fully encapsulate a crawl space. Make sure that your vapor barrier has a low “perm” rate and that it is at least 14mil thick. If you’re planning to use the space for storage make sure that a flexible sub-flooring product is also placed on top of the vapor barrier to protect it.

2.) Cover the walls too – all too often contractors forget to also encapsulate the walls of the crawl space when installing a vapor barrier. This can still allow water and moisture into the basement and therefore render the whole project useless. Take care to make sure it’s installed properly.

3.) Don’t use sprays. – Sealants and sprays aren’t designed to be applied on the interior of the basement. They are good in many circumstances as the “first line of defense” but as the last, they can’t hold the pressure and moisture trapped in a wall.

4.) Install a sump and a dehumidifier – to totally control the moisture level in the crawl space it’s imperative that you have a sump pump and a dehumidifier installed. Moisture will still exist, although not to dangerous levels, but a sump will remove any liquid water your encapsulation traps, and the dehumidifier will deal with any residual moisture that naturally collects in the space.

Crawl Space Repair Without a Fan or Vent

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The single best thing you can do to eliminate moisture and odors coming from the crawlspace is to apply a heavy sheet of plastic. Plastic wrap comes in clear or black and in different thicknesses. Purchase either color and with a thickness of at least 6 mil or better yet 10 mil.

Roll out the plastic so that all of the crawlspace floor is completely covered with plastic. When you have to cut the plastic to go around something, be sure to cover the cut with additional plastic or lap the original layer over the cut out. It's OK to use duck tape on the plastic vapor barrier as well. Just be sure to not have any voids in the plastic where moisture and odors can still get through.

The walls of the crawlspace should be covered as well to better eliminate moisture concerns as they can harbor condensation, a major source of moisture issues. Just roll out extra length of plastic so that you can run it up the crawlspace wall and using the stapler, tack along the ledger board located just above the concrete block or poured wall.

If you eliminate odors, moisture from the crawlspace and other undesirable elements coming from the ground beneath your home, your family will be living in a much healthier environment.

Although this task can be accomplished by yourself, it will be much easier if you can get a buddy or helper to go into your crawlspace and aid in the rolling out of the plastic barrier.

6 mil plastic is fine, however, if you can find thicker plastic (greater than 6 mil) then it will be much harder to rip or tear as you move along the crawlspace.

5 Helpful Tips For When it is Time to Encapsulate Your Crawl Space

crawl space conversion

There are three basic types of foundations in use today in the construction of a home.

Slab Foundations

A slab foundation is a foundation built directly on the soil with no basement or crawl space. Slab foundations are common in areas where soil conditions are not suitable for a basement, and are the most common foundation found in warmer areas such as Florida, Arizona, California and Texas, or anywhere where the depth between the soil and stable underlying rock is very shallow. Slabs are the quickest and cheapest foundation because they require less labor, skill and materials cost. They consist of a concrete slab that is typically 6 to 8 inches thick. Embedded within the slab is a grid of supporting ribbed metal rods known as "rebar." Even in locations where basements are prevalent, slab foundations are typically laid to serve as the base for structures like garages, pole barns, and sheds. Slabs are the least expensive of the three main foundation types but provide no storage or utility space, as the home actually sits directly on a large platform of solid concrete. Slabs have the disadvantage of being difficult and expensive to repair when they settle and crack, and plumbing lines that protrude from the soil upward through the concrete can also be expensive to repair. In areas where the underlying soil is thick or prone to excessive expansion and contraction, cables are embedded which can be tightened to provide better horizontal support and minimize the width of cracks.

Crawl Space (Pier and Beam) Foundations

A pier and beam foundation consists of either vertical wood or concrete columns (piers) that support beams or floor joists above the ground. The areas between the soil and the bottom of the house floor is known as the crawl space. These foundations are built either at ground level or over a shallow excavation that varies in depth, but is commonly about 36 to 40 inches deep. The best crawl space foundations have a load-bearing concrete perimeter wall and concrete or steel piers, both having footings below the freeze line of the soil, along with a good barrier over the soil to keep moisture under control. Less expensive versions have no load-bearing perimeter walls, piers with shallow footings, and no moisture barrier at all over the soil. Crawl spaces that enclosed by a wall or by skirting must have vents on every side to allow air to circulate and help keep the soil dry under the home. These vents must be configured to prevent the entry of rodents and snakes. Crawl space foundations are most often used in areas where there is heavy clay content in the soil that can severely damage (crack) slab foundations, or in waterfront or flood prone building sites where the necessary floor height to prevent water penetration of the living space must be higher than a slab can normally provide. The primary advantages of crawl space foundations are that plumbing lines are readily accessible for repairs, and foundation settlement problems are easier and less expensive to correct than with slab foundations. A primary disadvantage occurs when these foundations are not properly maintained or are constructed without adequate ventilation, allowing water or pests to cause damage. Crawl space foundations without adequate insulation applied to the bottom of the house floor can be very energy inefficient in a cold climate.

Basement Foundations

A basement is a type of foundation which includes an accessible space between the soil and the bottom of the first floor of a home. This foundation provides living space below the home, below the ground elevation. It is basically a slab foundation with walls and a floor. Basements are most often built in cold weather climates such as the Northeast, Midwest and Rocky Mountains, and in places where the cost of excavation is not prohibitive. Basements start with a hole approximately 8 feet deep, however, some homeowners will opt for a 9 or 10 foot deep basement wall to increase height and volume of useable space. The floor and walls are built, then the house itself is built over that. Basement foundations have the advantage of providing useful space for utilities, mechanicals systems, and storage not available in the previous two types of foundations. The primary disadvantage of basements is that because they are mostly below ground level, they are vulnerable to leakage, mold formation, and flooding. Basements in wet climates must always have a working drain and pump in the floor to combat flooding.