Many homes that lack a basement often leave crawl spaces underneath the ground floor. This is not only true of mobile homes, but ranch style and even large homes that lack a full-sized basement. These areas are left unseen, and therefore tend to be ignored. In cases where a basement has a dirt floor, encapsulation is also an option.

Unfortunately, crawl spaces become a major source for numerous health and safety issues. Rodents, birds, and other pests sometimes take up residence.

Poor insulation can lead to heat loss, and poor ventilation may lead to mold. Dust and allergens will also accumulate within these disused portions of your home.

What is Crawl Space Encapsulation?

The primary function of encapsulation is to create a barrier within your crawl space to insulate against humidity. In the process, it also aids in preventing large pests and utility costs. The process is very thorough and has become one of the most popular home improvements over recent years.

Pros and Cons

There are numerous advantages to encapsulation. The primary function of the process is to reduce moisture and the risk of mold.

In creating an airtight barrier, insects and animals are also prevented from entering the space. Gasses released by soil as well as dust and allergens are also effectively blocked, leading to improved air quality.

Finally, as a result of the additional insulation, you may notice reduced utility bills. Unlike many other home improvement projects, the only disadvantages spring from the initial cost and poor installation.

Can This Be a DIY Project?

While it is entirely possible to encapsulate on your own there are numerous problems which may arise from using incorrect materials or not installing them correctly. If you plan to do the work yourself, be sure to avoid cutting corners and follow any instructions carefully. Note that some systems are only available through authorized contractors.


The cost for encapsulation varies widely, based upon the contractor, the materials and the size of the space. According to, the average installation cost ranges between $5,000 and $7,000. The cost may be as cheap as $2,000 if you do the installation yourself, and hiring a contractor who uses the CleanSpace system may cost as much as $14,000.

It is important to check around when hiring a contractor. Not only may some contractors charge more for less, but they may use inferior products. Always be sure to ask about a warranty that covers poor installation and check the fine print. This could save thousands of dollars if a problem arises.


As there are likely pipes and wires running through your crawl space, it may be necessary for a plumber or other professional to perform maintenance or repairs within the space. This activity should not damage the vapor barrier if you have used thicker plastic or a quality vapor barrier system such as CleanSpace or SilverBack.

Today’s Homeowner Tips

Note that any work near an external wall may require a seal to be broken and later replaced. This is especially true of water supply pipelines.

The Basic Process

While materials may vary slightly between contractors, the basic process remains the same. This process has been developed over the course of a decade to eliminate as many flaws as possible. Skipping steps, even those which seem redundant or excessive, may result in problems over time.

Step 1: Preparing the Crawl Space

Whether you are encapsulating a crawl space or a partial basement with a dirt floor, the first step is essential. All debris, especially sharp rocks or anything else which may puncture the insulating plastic needs to be removed. The ground is then graded to create the most level surface possible.

Step 2: Sealing

Any external openings in the side walls, such as vents and doors must be sealed. Pipes or wires coming from the outside must also be properly sealed. This will block unwanted air flow and also help to waterproof the space. Depending upon the contractor, the material used may be plastic or foam.

Step 3: Insulation

An insulating layer of plastic is added to the walls and floor. The plastic used for the floor should be at least six millimeters in thickness, should overlap by at least one foot, be stapled down, and cover the entire area. At this thickness, the plastic will be durable enough to endure plumbing, termite inspections, and other disturbances. Wall plastic should use metal fasteners and allow for a six inch gap from the sill plate to help facilitate termite inspections.

Step 4. Conditioning

Once the space has been sealed off, the existing moisture must be removed. This may consist of vents leading into the living area and/or the installation of a dehumidifier unit. If your home is located in an area prone to flooding, you may also need to add a sump pump or flood alarm. This step is the most commonly excluded when attempting to save money, even though it is one of the most important.

Issues with Crawl Space Encapsulation

After installation, there should be no issues with your crawl space. However, numerous problems may arise from using the wrong materials or cutting corners. The following are common complaints and their probable causes.


A properly encapsulated crawl space should not be producing odors. Musty or moldy smells may arise from moisture seeping into areas which have not been properly taped or inferior materials that have become damaged. A chemical or bleach smell is most often caused by the use of improper materials such as PVC which may also result in damage to tape or tearing in the lining itself.

Excess Moisture or Humidity

One off the most important jobs of encapsulation is to provide a barrier against moisture. If your humidifier is running constantly, you have a damp odor, or the crawlspace is flooding, the space has not been properly sealed. This is most often caused by the contractor cutting out steps, such as proper taping. Poor air flow may also be a contributing factor, and may lead to mold or other costly damages. As this is often the first item to be cut when attempting to save money, it is also often the source of condensation and other moisture issues.

Performing Inspections

While a properly encapsulated crawl space greatly reduces the risk of mold and unwanted guests, even the best barriers may suffer damage. Therefore it is best to perform inspections of the crawl space at least twice per year. You may choose to schedule an annual professional inspection to coincide with termite or other regular inspections or handle the job yourself.

The first item checked during the inspection is moisture level. There should not be high humidity, condensation, or visible water present. Moisture may suggest a tear or gap in the plastic vapor barrier. Examine the barrier for damage, making sure that it covers the entire floor and individual pieces are overlapped and properly anchored. Performing a radon test at this time is advisable.

Next, check any supports or joists for signs of looseness, mold, or dry rot. The latter may lead to small gaps in your barrier through which additional moisture may enter. Damage to support beams creates a risk of structural damage and should be addressed immediately. Likewise, damage to air ducts may increase the risk of problems.

Finally, look for signs of rodent activity, such as droppings or chew marks. Insect damage, especially from termites, may also be visible. These signs may suggest damage to the barrier and a possible infestation in other portions of your home.

Additional References

Energy Star released a fact sheet regarding crawl space insulation, its benefits, and guidelines for installation. While primarily meant for new construction, the guidelines may still be applied to an existing crawl space or when adding an extension to your home., LLC is the official website for the manufacturers of the SilverBack vapor barrier and other quality encapsulation products. Not only does the site allow you to purchase materials direct, it also contains articles and guides to aid in installation and troubleshooting.

Editorial Contributors
avatar for Henry Parker

Henry Parker

Henry Parker is a home improvement enthusiast who loves to share his passion and expertise with others. He writes on a variety of topics, such as painting, flooring, windows, and lawn care, to help homeowners make informed decisions and achieve their desired results. Henry strives to write high quality guides and reviews that are easy to understand and practical to follow. Whether you are looking for the best electric riding lawn mower, the easiest way to remove paint from flooring, or the signs of a bad tile job, Henry has you covered with his insightful and honest articles. Henry lives in Florida with his wife and two kids, and enjoys spending his free time on DIY projects around the house. You can find some of his work on Today’s Homeowner, where he is a regular contributor.

Learn More