Moisture in your crawl space can cause several problems for your home, from mold growth to wood rot and even attract pests. Installing a crawl space vapor barrier is one way to protect your home from moisture damage. A crawl space vapor barrier is a thick sheet of plastic installed over the dirt floor of your crawl space. It’s designed to prevent moisture from the ground from seeping into your home.
What Is A Crawl Space Vapor Barrier?
A crawl space vapor barrier, sometimes called a vapor diffusion retarder, is a very low permeability rating material. It blocks water vapor transmission, essentially sealing the crawl space to stop moisture intrusion into your home’s subfloor structure. Vapor barriers can be installed on the ground, walls, or even the ceiling of a crawl space, depending on your needs.
This impermeable barrier helps prevent moisture from seeping up from the ground. This moisture can then get into the air in your crawl space and subsequently into your home.
Why You Need Crawl Space Vapor Barriers
If your crawl space isn’t adequately protected from moisture, it can cause several problems, including:
- Mold growth
- Wood rot
- Musty odors
- Increased energy costs
- Pest infestation
By correctly installing a vapor barrier in your crawl space, you can prevent these problems from occurring. This can improve indoor air quality and protect the structure of your home from harmful moisture damage. It’s important to address moisture problems swiftly, as damage can accrue over time, resulting in structural problems for your home in the long run. In fact, moisture is a main contributor to mold growth.
How Crawl Space Vapor Barriers Work
Vapor barriers act as a protective layer against ground moisture because vapor naturally rises. It then seeps upward through porous building materials. Most crawl spaces have dirt floors. This bare earth makes the space extremely vulnerable to this ground moisture since the dirt readily absorbs it.
Essentially, a crawl space vapor barrier acts like a big plastic liner. Installed in direct contact with the ground, it blocks water vapor from permeating the surface. Installing this heavy plastic sheeting interrupts the natural path of vapor migration. That being said, if you have other sources of moisture, such as plumbing leaks or ventilation problems, installing a crawl space vapor barrier alone will not address those issues.
Different Types of Crawl Space Vapor Barriers
There are a variety of different crawl space vapor barriers available on the market today. These vapor barriers are made with varying types of plastic. Some of the most popular options include:
Polyethylene:
This common plastic is what trash bags and sandwich bags are made of, just in different thicknesses (or “mil”). Polyethylene sheeting is often used for crawl space vapor barriers. It offers excellent moisture resistance at an affordable price point, making it a trendy choice among homeowners in 2024. Polyethylene is available in several different thicknesses (called “mils”). The most common mil thicknesses are 6, 10, and 20 mil.
It is usually recommended to use a vapor barrier at least 10 mil thick, which will help ensure optimal protection from vapor. The American Society of Home Inspectors even recommends Polyethylene, stating, “cross-laminated polyethylene sheeting… has superior durability, puncture resistance, and tear strength.”
Reinforced Polyethylene:
Reinforced Polyethylene is your standard polyethylene plastic but with an added layer. The extra layer of fabric or mesh grid reinforcement is laminated onto one or both sides to enhance strength, tear resistance, and durability. The addition of this scrim makes it significantly more robust and sturdy while retaining flexibility. This added durability is usually a worthwhile investment because, according to Inspectapedia, “punctures from rocks, debris, or tools are a primary reason vapor barriers fail.”
Other Materials:
Although not used very often, some other options available include EPDM rubber and chlorinated Polyethylene. However, according to the Building Science Corporation, “Polyethylene has proven to be remarkably durable over time when used as a crawl space ground cover. EPDM (rubber) sheets can emit an odor. Additionally, chlorinated polyethylene (CPE) sheets also have an odor.”
Things to Consider When Shopping For a Vapor Barrier:
Once you have decided on what material type of crawl space vapor barrier will work best, it’s time to start thinking about these additional factors. Addressing these will help you choose a barrier best suited for your home and individual needs.
Thickness:
Crawl space vapor barriers can range in thickness. Generally, a six mil vapor barrier suffices in some cases, while a 20 mil option offers better durability and puncture resistance for the investment in most crawlspaces. You will need to have a professional crawlspace company assess your crawl space to make an informed decision.
Crawl Space Coverage Area:
Measure the entire area’s square footage for accurate material estimates. Get the right size to minimize waste. To ensure accurate coverage, consider factoring in some extra for overlap when joining multiple sections together. When calculating the crawl space area, you might need to account for obstacles like support beams or pipes.
Code Compliance:
Before starting the project, your crawlspace contractor will ensure the chosen crawlspace vapor barrier meets local building code requirements. Your vapor barrier installation must follow the International Residential Code and local building regulations.
Budget:
Vapor barriers have various prices that usually depend on thickness, size, and the addition of a reinforcement layer. By understanding your budget constraints, you can choose the best option for your individual situation and avoid budget surprises later.
Product Warranty:
Be sure to review the included product warranty carefully. Many manufacturers back their crawl space vapor barriers with warranties ranging from 10 years to even a lifetime. It’s a wise choice to choose a product with a more robust warranty if your budget allows, as it can provide additional peace of mind and protection in the long run.
Crawl Space Vapor Barrier Installation
While DIY is technically possible, working with experienced and professional waterproofing contractors, helps to ensure correct installation so that any warranties are not voided. This will maximize the effectiveness of the vapor barrier and minimize potential risks like vapor barrier damage. During the installation process, the contractor will use fasteners to secure the vapor barrier properly.
They will pay close attention to sealing any seams or penetrations. Proper sealing is critical for preventing moisture intrusion. Sometimes, a sump pump may be recommended as part of a comprehensive moisture control system. A sump pump helps remove excess water accumulating in the crawl space.
Conclusion
A crawl space vapor barrier is a smart investment for any homeowner concerned about excess humidity in the crawl space, leading to potential problems in the future. Installing a high-quality vapor barrier in your crawl space can provide numerous benefits, such as:
- Reduced moisture and humidity levels
- Prevention of mold growth and mildew
- Protection of the home’s foundation
- Improved indoor air quality
- Increased energy efficiency
A proper crawl space vapor barrier prevents these varying issues and can save you a lot of hassle and home restoration expenses in the long run.
