Crawlspace Encapsulation: Everything You Should Know

Written By Adam Paul - Waterproofing Expert

Crawlspace encapsulation is a moisture and vapor control method that seals the crawlspace beneath a building. Crawlspace encapsulation involves installing a reinforced polyethylene vapor barrier over the soil and foundation walls, along with sealing all vents, joints, and access points in the crawlspace. The main purpose of crawlspace encapsulation is to block ground moisture and outside air from entering the crawlspace.

Crawlspace encapsulation helps to prevent indoor moisture content, improve energy efficiency, protect the structure from water and vapor damage, improve indoor air quality, and increase the property value. You should encapsulate the crawlspace when you observe signs of excessive moisture, air leakage, or material deterioration.

You will need a vapor barrier, sealing tapes, insulation materials, a dehumidifier, a sump pump, and a French drain for a successful encapsulation process. As well as you should follow the 9 steps that Aqviz experts follow in every crawlspace encapsulation project. We highly recommend that you should not do it DIY. Instead this you can use an alternative method. You should always hire a professional for this always for better results. There are both pros and cons for crawlspace encapsulation. We highly recommend that you inspect the crawlspace and take the most suitable action to protect it from water and vapor.

What is Crawlspace Encapsulation?

Crawlspace encapsulation is a moisture and vapor control method that seals the crawlspace beneath a building. Crawlspace encapsulation involves installing a reinforced polyethylene vapor barrier over the soil and foundation walls, along with sealing all vents, joints, and access points in the crawlspace. The crawlspace encapsulation process also includes using a dehumidifier, sump pump, and rigid foam insulation to completely isolate the area from ground moisture and outdoor air.

Crawlspace encapsulation transforms the space into a dry, enclosed zone that blocks humidity, prevents mold growth, and protects structural components. Crawlspace sealing helps maintain consistent indoor air quality, lowers energy costs, and increases the durability of insulation, wood, and mechanical systems within the home.

What is the Main Purpose of Crawlspace Encapsulation?

The main purpose of crawlspace encapsulation is to block ground moisture and outside air from entering the crawlspace.

More than that, there are other purposes of crawlspace encapsulation, including preventing mold and mildew growth, protecting structural integrity, improving energy efficiency, eliminating pest infestation, and enhancing the indoor air quality in the home.

What Are the 5 Benefits of Crawlspace Encapsulation?

Crawlspace encapsulation offers multiple long-term advantages by turning the crawlspace into a sealed, controlled environment.

The five major benefits of crawlspace encapsulation include

Prevent indoor moisture content: Crawlspace encapsulation blocks up to 98% of ground vapor and condensation.
Improve energy efficiency: Crawlspace encapsulation lowers heating and cooling costs by 15–25% annually.
Protect structure from damage: Crawlspace encapsulation prevents wood rot, corrosion, and concrete damage.
Improve indoor air quality: Crawlspace encapsulation reduces allergens, mold spores, and musty odors.
Increase property value: Crawlspace encapsulation adds resale appeal and extends the building’s lifespan.

When Should You Encapsulate The Crawlspace?

Crawlspace encapsulation should be done when the crawlspace shows signs of excessive moisture, air leakage, or material deterioration.

You should encapsulate the crawlspace when you see the following problems occur.

Standing water or damp soil in the crawlspace
High humidity level in the crawlspace
Musty odors rising from the crawlspace
Visible mold and mildew growth in organic materials in the crawlspace
Sagging insulation or wood rotting in the crawlspace

What You Need For Crawlspace Encapsulation?

Crawlspace encapsulation requires specific materials designed to create a durable, airtight, and moisture-resistant barrier. These are the essential materials for crawlspace encapsulation according to our Aqviz experts.

Vapor barrier (6-20 mil polyethylene): Vapor barrier covers ground and walls to block moisture in the crawlspace.
Seam tape or butyl tape: Sealing tapes seal overlaps and joints in the vapor barrier.
Rigid foam board insulation: Insulates foundation walls and improves energy efficiency in the crawlspace.
Dehumidifier (energy-efficient): Crawlspace dehumidifier maintains relative humidity below 60% in the crawlspace.
Sump pump with basin and check valve: Crawlspace sump pump removes groundwater and prevents crawlspace flooding.

How to Encapsulate the Crawlspace?

This is the 9 step by step guide for crawlspace encapsulation according to the Aqviz experts.

9 Step-by-step guide for crawlspace encapsulation.

Inspect and clean the crawlspace: Remove debris, old insulation, and sharp objects in the crawlspace. Identify damage, mold, or pest infestations that must be addressed before crawlspace sealing.
Repair structural and plumbing issues: Fix cracks, leaks, and damaged wood framing in the crawlspace. Then replace or treat mold-affected areas and seal wall penetrations with foam or caulk.
Grade and level the crawlspace floor: Ensure proper slope toward a drainage point in the subfloor. If water intrusion exists, install a French drain system around the perimeter.
Install a sump pump: Position a sump basin at the lowest point of the crawlspace. Then connect the sump pump to a check valve and discharge pipe for groundwater removal.
Seal crawlspace vents, access doors, and openings: Use foam board, caulk, and weatherstripping to block air leaks and insect entry through wall vents, pipe gaps, and entry doors.
Apply vapor barrier on the ground and walls: Lay a 12-20 mil polyethylene sheet across the crawlspace ground, then extend it 6-12 inches up the walls. Overlap seams by at least 12 inches and seal with butyl tape or poly tape.
Install crawlspace wall insulation: Attach rigid foam insulation boards to foundation walls with adhesive or mechanical fasteners.
Set up a dehumidifier in the crawlspace: Choose a crawlspace-rated dehumidifier sized to the space. Place it on a concrete pad or a hanging shelf and connect a drainage line to the sump or exterior.
Perform final sealing and testing: Recheck all seams, overlaps, and corners for gaps in the crawlspace. Monitor relative humidity and ground moisture for the next few days to confirm effectiveness.

Can You Encapsulate Crawlspace Diy?

No, crawlspace encapsulation should not be attempted as a DIY project due to its complexity, health risks, and technical requirements. The process involves handling vapor barriers, insulation, dehumidifiers, and sump pumps, all of which require specialized tools and expertise to install properly. A poorly done DIY crawlspace encapsulation can trap moisture instead of blocking it, leading to mold growth, wood rot, or even foundation damage.

What if Crawlspace is not Encapsulated?

If the crawlspace is not encapsulated, it may cause mold and mildew growth, wood rotting, wood warping, structural decay, metal corrosion, musty odors, higher energy bills, pest and termite infestation, reduce indoor air quality, and reduce the property value over time.

What Are the Pros and Cons of Crawlspace Encapsulation?

Crawlspace encapsulation offers major advantages for moisture control and home efficiency, but it also comes with challenges. These are the pros and cons of crawlspace encapsulation.

Pros of crawlspace encapsulation

Protect the crawlspace from moisture
Improve indoor air quality in the home
Increase energy efficiency
Prevent structural damage
Control pests and termites successfully

Cons of crawlspace encapsulation

Need sped higher cost for full encapsulation
Frequent maintenance required
Installation is complex
Future plumbing and electrical repairs can damage the vapor barrier
Not suitable for all climates

What are the Alternatives for Crawlspace Encapsulation?

If the crawlspace is not possible to encapsulate, there are 3 alternatives: crawlspace waterproofing, crawlspace insulation, and foam installation in the crawlspace.

Crawlspace waterproofing focuses on managing water entry using crawlspace drainage systems, sump pumps, and sealants, but it doesn’t block vapor or insulate the space.

Crawlspace insulation helps control temperature using fiberglass or foam board, yet it lacks vapor barriers and air sealing found in encapsulation.

Crawlspace foam installation involves spraying closed-cell foam to insulate and reduce air leakage, but it can’t control ground moisture alone without a vapor barrier system.

How Much Does It Cost to Encapsulate 1000 Sqft Crawlspace?

The average cost to encapsulate a 1,000 sqft crawlspace ranges between $5,000 and $15,00,0 depending on materials, labor, and site conditions. Crawlspace encapsulation pricing varies based on the mil thickness of the vapor barrier, insulation type, moisture level, and whether additional systems like a sump pump or dehumidifier are required.