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How to Encapsulate a Crawl Space (Step-By-Step Guide & Tips)

How to Encapsulate a Crawl Space (Step-By-Step Guide & Tips)

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Crawl space encapsulation is the process of completely separating the area beneath your house from the actual living space inside your home. Its purpose is to prevent the air in the crawl space from moving to your living environment.

Besides creating a healthier atmosphere in the house, sealing off the crawl space helps keep the floors warmer in the winter and cooler in the summer, reduce energy bills, prolong the lifespan of your HVAC system, and curb pest attacks and mold growth.

Today’s article is a step-by-step guide on how to encapsulate a crawl space.

How to Encapsulate a Crawl Space

Crawl space encapsulation seems like a hard job at first, but it’s a lot less of a hassle than you think. Breaking it down into simple steps makes for an easy project that you can finish in a few days.

Step 1: Prepare the Crawl Space

First things first, you need to make sure that your crawl space is ready for encapsulation.

The difficulty of this step depends on the condition of the house and its age. If you or the previous owners didn’t pay attention to the upkeep of the crawl space, chances are you’ll have a hefty prep and cleaning job waiting for you.

On the bright side, even if your crawl space needs a lot of work to make ready, this step calls for the most effort. So everything after it will be easier.

Not to mention, cleaning and clearing the crawl space doubles as an overall wellness check for the house.

Here’s what crawl space preparation involves:

Illuminate the space

How can you do anything inside your crawl space if you can’t even see down there? This is why you need to provide adequate lighting throughout the space.

The best option is natural sunlight. Look for vents around the crawl space and open them to let in the light.

If you can’t find any vents, you’ll have to use alternative light sources such as construction string lights or battery-powered lanterns/flashlights.

Remove old encapsulation

Start by inspecting the crawl space for any old foundation insulation, vapor barriers, or other encapsulation materials. You shouldn’t apply new encapsulation over older materials; it’ll probably fail and you’ll have to redo the entire process.

If you find old encapsulation, remove it beginning from one side of the house to the opposite. Roll up the material carefully and if you come across torn pieces, throw them in a heavy-duty garbage bag.

While taking down old encapsulation, wear protective eye goggles, a face mask, and gloves to prevent exposing yourself to dust, dirt, and other potentially harmful debris.

Clear up the space

Next, you need to clear up the crawl space of any junk or unwanted items lying around.

Grab a heavy-duty garbage bag and start combing through your crawl space from one side to the other. Get rid of stuff like rocks, leaves, concrete, metal scraps, nails, sticks, trash, and so on.

Keep your protective gear on as you’re cleaning. At the end of this step, your crawl space should only have dirt covering its bottom.

Address holes and gaps

Now is the time to take care of any holes or gaps present across the bottom of your crawl space and the house’s foundation.

For the bottom of the crawl space, use a shovel to move gravel or sand into holes, especially those deeper than 1 or 2 inches. This is crucial to prevent standing water that can pool in holes, increasing humidity within the space and posing a safety hazard.

After that, check the foundation for compromised entryways or gaps that may allow the elements or animals into your crawl space.

Fix any issues and enforce the entryways with wired mesh to prevent critters from getting inside and damaging the new encapsulation.

Check plumbing and electricity

Finally, examine the plumbing and electricity systems that may be present within the crawl space.

Are there any damaged pipes? Can you see any loose wiring? Resolve such problems before you start working on the encapsulation process.

Step 2: Determine the Area of the Crawl Space

Use a measuring tape (100 feet) to find out the width, length, and height of your crawl space. Record each number on your phone or write it down after measuring so you don’t forget.

Don’t take measurements from outside the crawl space as they’ll probably end up in inaccurate calculations. If your crawl space is an ‘L’ shape, take full measurements for both sections.

If the crawl space is any other shape, divide it into squares and/or rectangles and measure them. Be sure to factor in any structures such as support pillars as they can affect the calculations and the encapsulation process.

Once you have all your measurements ready, sketch the outline of your crawl space using the width, length, height, and other structures. Add labels and be as precise as possible.

Now, determine the total area of the crawl space using the measurement:

  • If your crawl space is a square or rectangle, multiply the width by the length to get the area.
  • If your crawl space is an ‘L’ shape, multiply the width of each section by its length to get the area of both sections then add them to determine the total area.
  • If the crawl space is any other shape, calculate the areas of the square and/or rectangle portions and then add them to get the total area.

Once you figure out the total area of the crawl space, add 10 percent to it to make up for any waste or errors in measurement. For example, if you calculate the total area to be 10 square feet, the final area should be 11 square feet.

Additionally, calculate the area of the lowest 6 inches of the foundation walls and other structures within the crawl space.

Step 3: Purchase the Right Vapor Barrier

When buying a vapor barrier, its thickness should be 12 Mil (.012 inches) or more. Such thickness offers long-lasting durability along with sufficient insulation.

If you go thinner, the vapor barrier is more likely to fall apart and leak moisture into your crawl space.

Step 4: Install the Vapor Barrier

Start rolling out the vapor barrier along the width of the crawl space, and make sure you roll out one line at a time.

Unroll slowly and use a box cutter to cut the vapor barrier when you reach the other end of the crawl space.

After that, cut enough of the vapor barrier to cover the 6 bottom inches of the foundation and other structures. Additionally, cut around any structures to fit the vapor barrier properly across the ground.

Cut tailored vapor barrier pieces to apply to the structures and create a seamless seal. Tape those pieces to the main barrier piece on the ground.

For security, use fabric stakes to fasten the vapor barrier to the ground as you unroll it. A stake every 4 feet or so should be enough to keep everything in place.

Don’t forget to overlap your vapor barrier lines by 2 inches with each new line you roll out to prevent moisture from seeping between the lines.

Tape any seams on the vapor barrier to further protect against moisture. Also, use foundation pins to attach the vapor barrier to your foundation.

Step 5: Add Insulation to Exposed Areas

Cut moisture-proof insulation and secure it onto any exposed areas across the foundation using foundation pins.

This is especially important for crawl spaces residing beneath living areas as it helps increase your energy efficiency and better regulate the temperature inside the house.

Step 6: Install a Dehumidifier

Any encapsulated crawl space needs a drying mechanism to prevent the buildup of moisture inside, which protects the structural integrity of the area and keeps mold growth at bay.

A dehumidifier is one of the most efficient drying mechanisms you use in an encapsulated crawl space.


Do I Need a Permit to Encapsulate My Crawl Space?

Some places require you to obtain a permit for crawl space encapsulation, but other locations don’t. So it depends on where your house is.

Do I Need a Dehumidifier in My Encapsulated Crawl Space?

Yes, a dehumidifier is necessary to maintain low moisture levels.

Can You Encapsulate a Crawl Space Without a Dehumidifier?

Every encapsulated crawl space needs a drying mechanism, and a dehumidifier is the most efficient one. However, other ways exist, such as the air supply method.

Final Thoughts

There you have it, a step-by-step guide on how to encapsulate a crawl space. The process starts with the preparation and cleaning of the crawl space, followed by measuring its total area.

After that, you need to install the vapor barrier, insulation, and a dehumidifier.

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