Is Crawl Space Encapsulation A Good Idea – The Pros And Cons

Crawl spaces act as a buffer between the house and the earth underneath. However, did you know these spaces can become a potential health and structural hazard? We consulted with the experts to unearth how this is possible and what can be done to solve this problem.

Despite a crawl space having several functions, it can also be an area of potential harm to you or the structure of your home. One of the ways of mitigating this problem is by encapsulating it. But first, let us look at some of the problems you may encounter with this space:

  • Water entering the crawl space
  • Formation of condensation
  • Standing water
  • Falling insulation
  • Growth of mold and mildew
  • Musty orders
  • Warping floors
  • Infestation of insects and rodents

Crawl spaces need not be a nuisance, nor should they cause undue distress. Continue reading to understand how problems can emanate from this space and how to overcome them.

Cinder Block wall in Basement with spray foam insulation, Is A Crawl Space Considered A Basement?

Potential Problems In Your Crawl Space

Even if you do not frequent your crawl space, it should not be neglected. Some of the issues that can develop here are discussed below:

Water Entering The Crawl Space

closed cell spray foam insulation in basement crawl space

Water can saturate in the ground after a heavy downpour and eventually seep through the foundation walls and into your crawl space.

In addition, water can trickle into this space from leaking basement window wells and windows, overflowing gutters, outdoor roof drainage, or grading issues. Also, a burst or leaking pipe can direct water into the crawl space.

Formation Of Condensation

When humid air from outside enters your crawl space through the vents, condensation takes place as it comes into contact with the cool air forming dew. This results in patches of water forming on the wall, or your HVAC conditioner.

Standing Water

Standing water can form due to poor landscaping or drainage or after too much rainfall. In some cases, this water recedes downwards by itself causing water to enter a crawl space through cracks in the foundation.

Chalky or white marks on your foundation are a sign that there is standing water in your crawl space.

Falling Insulation

Insulation that is falling apart can be a medium in which water moves upwards, causing damage to the sub-flooring and joists.

Growth Of Mold And Mildew

Mold thickly covers a wall

When there is moisture in your crawl space, mold and mildew can grow, causing health problems like allergies or respiratory problems. The floor joists can also rot if it soaks in moisture leading to expensive repairs.

Musty Odors

Molds can produce musty smells, which may pass through cracks in your walls or sub-floor and into your home.

Warping Floor

Moisture can move through the sub-floors, causing damage to the interior floors. This is noticeable when the hardwood floors warp or buckle.

Infestation Of Insects Or Rodents

Insects and rodents can make your crawl space into a home. They can find their way through tiny open spaces in the foundation, missing vents, or under poorly fitted doors.

How To Encapsulate Your Crawl Space

Encapsulation refers to the prevention and reduction of humidity by sealing the vents, lining the walls and floor with white plastic sheets, and conditioning the crawl space. This keeps away moisture, insects, and rodents, while the conditioning aerates the space.

For enhanced moisture prevention and durability, plastic sheets ought to be between 10 and 20 millimeters thick. Caution should be observed when fixing it all around the crawl space to prevent tears that can cause moisture to seep through.

The following is a step-by-step guide on how to encapsulate a 1,000 square feet of crawl space, which takes between 8 and 10 hours to complete:


  • Breathing mask
  • Drill and masonry bits
  • Knee pads
  • Lots of lighting – headlamps, flashlight, or utility lamps
  • Marker
  • Measuring tape
  • Pair of gloves
  • Protective eye-wear
  • Rubber paint roller - optional
  • Trash bags
  • Utility knife


  • Barrier seam tape
  • Concrete screws
  • Double –sided construction tape
  • Plastic sheet
  • Mechanical fasteners or termination bars

The steps are as follows:

1. Preparation Of Crawl Space

Cinder Block wall in Basement with spray foam insulation

Preparing your crawl space may be the most difficult part of your job because its condition will depend on how old your home is and how well the previous owners took care of it.

Get rid of any standing water that may be a potential risk to electrocution when you bring lighting or power into the area. Once it’s safe to go in, clean the space by removing debris, sharp rocks or objects, old insulation, or old plastic sheets.

Next, you may want to have the wiring checked by an electrician or the plumbing by a plumber. Check the wood for any damage and consult the professionals if repairs are needed. Decide too on how you will condition your crawl space.

2. Cover The Walls

Apply the sticky double-sided construction tape to your masonry wall, onto which the insulation is held in place before using a mechanical fastener to secure it.

Remove the release liner little by little as you move slowly along the wall. Use a rubber paint roller to press the tape firmly on the wall, preventing a sticky mess.

Detach the release liner that is exposed, and then fix the sheet firmly on the walls, allowing the extra material to lay over the floor horizontally allowing it to overlap on the groundsheet.

Bear in mind to leave a tiny space at the top of the masonry wall for termite inspectors to carry out their job. This is per the building code.

Allow the plastic sheet to extend much higher than the double-sided tape, and after fixing it, secure it with a mechanical fastener such as termination bars.

Drills holes into the concrete to easily fix the concrete screws.

3. Cover The Pipes

Tightly cover the pipes and any other penetrations with the plastic sheet, and seal it with seam tape. For easy application, use small sizes of the material.

Have a look at this seam tape on Amazon.

4. Cover The Columns

Follow the same procedure like that on the wall. Begin by applying the double-sided construction tape, then the plastic sheet, and last the termination bars.

Cut slits at the corners of the column to allow it to lay flat on the ground. This allows a seam to roll out on the ground without problems.

5. Cover The Entire Crawl Space

Roll out the plastic sheet to cover the entire crawl space, ensuring you overlap by not less than six inches at the seams, not forgetting to tape down the seams with a seaming tape.

This clear plastic sheeting is on Amazon.

The Pros And Cons Of Encapsulation

Crawl space fully encapsulated with thermoregulatory blankets and dimple board

What are the benefits and drawbacks of encapsulation? Let us find out from the table below:

Pros Cons
Moisture is reduced or eliminated Encapsulation can be expensive
Insects and rodents will not have any access to the crawl space Additional insulation may be required as recommended by the professionals
Less heat is lost translating to lower energy bills You may need to upgrade your HVAC system leading to more costs
You’ll get rid of musty smells that come from mold and mildew  
There’ll be a significant improvement in the air quality in your home  

Are There Alternatives To Encapsulation?

The alternative to encapsulation is the installation of the vapor barrier, a cheaper six millimeter black plastic sheet that is used instead of the white plastic sheet. It is also a lot cheaper because the vents are not covered, hence a humidifier is not required, and sump pumps are not needed either.

Is It Worth Encapsulating Your Crawl Space?

Encapsulation prevents the entry of moisture, thus wood will not rot which can lead to the weakening of the supporting structures. This method of keeping out moisture helps to add value to your home because it will remain in good condition. Hence if you may want to sell it in the future, you can fetch a good price.

How Much Does It Cost to Encapsulate?

crawlspace basement oil tank and plumbing

Encapsulation is not cheap, and though the costs vary as per the quality of materials used and labor, the average cost is between $5,000 and $10,000. Per square foot would cost between $3 and $7. So, the price of encapsulating a 1,500 square foot crawl space is around $7,500.

In Closing

Moisture can cause the growth of mold and mildew that can bring about health complications to your respiratory system and cause allergies. It can also cause nasty smells or rotting of wood that can lead to damages to the structural support.

These problems can be solved by encapsulating your crawl space, which involves covering it with a white plastic sheet, or instead, go for a cheaper option by using a vapor barrier that is made from a black plastic sheet. Other than increasing the value of your home, encapsulation has its advantages and disadvantages.

Check out our previous posts and learn how you can convert a crawl space to a basement, and how to efficiently use a humidifier:

Converting Crawl Space To Basement

When To Run Dehumidifier In Basement

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