Crawl Space Vapor Barrier
Repair & Installation

Northwest Crawl Space Services specializes in residential vapor barrier repair, replacement and installation services.

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A vapor barrier is essential for every crawl space that doesn’t have a concrete slab poured in it. Vapor barriers are typically made of polyethylene plastic sheeting, and they come in a variety of thicknesses and colors. The main purpose of a crawl space vapor barrier is to prevent moisture from coming up from the ground.

What makes up a standard home vapor barrier installation?

Materials: Local code requires a membrane minimum thickness of 6 millimeters, and the barrier must have a sealed color (can’t be clear/see through).

Installation: When installing a vapor barrier in a crawl space, we make sure to have correct overlap between the different pieces, stake it to the ground around the crawl space edges, eliminate any contact with wood (to prevent moisture attraction) and make sure not to leave any part of the ground.

What are some reasons you may need to install a new vapor barrier into your home's crawl space?

residential vapor barrier installation

Securing and taping the vapor barrier

Poor Installation: Unless it’s been done by a professional crawl space company, many older houses and even some new homes are very likely to have a deficient vapor barrier. Even experienced builders often tend to not perform quality work when it comes to vapor barrier installation in crawl spaces.

Wear and Damage: Depending on the quality and the thickness of the plastic, after several decades it’s inevitable that the plastic will start to crumble, fade and fall apart. In addition, other factors such as water, rodents and work performed in the crawl space can compromise and damage the plastic.

Vapor Barrier Services We Offer

Standard 6mil. Black Poly Sheeting: Used for normal crawl space with no special conditions sheeting.

Upgraded 10mil. Black or White Poly Sheeting: This is a thicker solution for crawl spaces with rough/rocky ground, steep slope, or existing drainage systems.

Encapsulation Grade – White 12mil., 14mil. or 20mil.: These grades of sheeting are usually used for a full encapsulation project, where the walls will also need to be covered, or any other situation where maximum moisture elimination is required.

Crawl Space Encapsulation Services

Encapsulation is essentially a project that modifies and changes the characteristics of your crawl space in order to create a cleaner and more moisture-controlled atmosphere. Other reasons for encapsulation include aesthetic and dust prevention.

When is crawl space encapsulation needed in your home?

Crawl Space Encapsulation Dehumidifier

Dehumidifier in encapsulated crawl space

Natural or Excessive Moisture: Under various conditions, some crawl spaces can experience extremely high moisture levels, even when they have proper ventilation. In the summer of 2021, we came across a crawl space in Sammamish that reached 100% humidity. (Normal humidity level in a crawl space should be anywhere around 50%-60%.) Excessive humidity means condensation starts to build up all over the crawl space. Wires, insulation, air ducts and structural wood can all get soaking wet, and the risk of mold, mildew, and damage is extremely high.

Health Issues and Allergies: In addition to moisture control, encapsulation can also benefit people with a sensitive immune system or allergies. A good amount of the air we breathe in the house comes from the crawl space. By fully sealing the crawl space and covering the entire ground and walls with heavy-duty plastic, you’ll notice a significant decrease in the amount of dirt and dust you breathe in. 

What are the benefits of full crawl space encapsulation?

Mold and Mildew Prevention: By monitoring and controlling the humidity in your crawl space, you can prevent growth of mold and mildew, which can be harmful and expensive to remove.

Increased Energy Efficiency: Encapsulation protects your crawl space from seasonal extreme temperatures. In this way it also helps keep your utility bills lower and prevents HVAC system burnout. 

Preventing Pest Infestation: A well-encapsulated crawl space should reduce your chances of getting pests like spiders, bugs and ants to virtually zero.

Improved Air Quality: Crawl space encapsulation improves the quality of the air you breathe by reducing the amount of dust and eliminating musty odor.

Our Crawl Space Encapsulation Service

Step 1 – Preparation: We begin by removing damaged insulation, old vapor barrier and debris as needed, then conduct full crawl space cleaning and sanitizing to ensure no dead rodents or other hazards are sealed under the plastic. We perform a full air seal to the foundation walls, including foundation vents.

Step 2 – Vapor Barrier Install: Our team meticulously installs heavy-duty vapor barrier all over the ground and walls, sealing all seams with extra-strong seam tape and securing it in place with metal anchors.

*If your crawl space has water issues, a professional drainage system should be installed prior to this step.

Dehumidifier: A professional dehumidifier will be matched to the size of the crawl space and will be installed and secured properly along with a condensation pump and drain pipes to safely channel condensation away from the crawl space.