Learn More About Crawl Space Encapsulation Liners

All of Americover® Crawlspace Vapor Barriers and Liners Meet or Exceed ASTM E1745 Class C Standard

Americover® crawlspace vapor barriers are multi-layered, extrusion laminated, and reinforced with a layer of polyester scrim reinforcement. The polyester scrim is placed between the layers of low density polyethylene to greatly enhance tear resistance and increase service life. All of Americover® crawlspace vapor barriers and liners meet or exceed ASTM E1745 Class C Standard (Plastic Water vapor retarders used in contact with soil or granular fill).

Choosing the correct vapor barrier for your crawlspace.

Before selecting which crawl space vapor barrier is best for your home, you must first understand what it is you expect it to do during its service life. There are 4 main characteristics to a successful crawl space vapor barrier: moisture protection, durability, longevity and value. You want a crawl space liner that is capable of handling the worst of conditions, meets ASTM specifications and has a Class A perm rating. Americover recommends the reinforced polyethylene vapor barrier for crawl spaces because it outperforms other liners with its perm rating alone.

Specifications for Vapor Retarders are as follows:

Vapor retarders are produced to meet specifications such as ASTM E1745, Standard Specification for Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs, or ASTM D4397, Standard Specification for Polyethylene Sheeting for Construction, Industrial, and Agricultural Applications. ASTM E1745 defines three classes of membranes with a single moisture vapor permeability rating and three levels of physical strength, Class A has the most resistance to tearing and puncture, and Class C the least.

What is a perm rating?

It is a standard measure of the water vapor permeability of a material. The higher the number, the more readily water vapor (in the gaseous state) can diffuse through the material. A perm rating of less than 0.1 is considered a Class I impermeable vapor retarder (which is also considered a vapor barrier); perm rating between 0.1 and 1 is considered a Class II semi-permeable vapor retarder; a perm rating between 1 and 10 is a Class III permeable vapor retarder; and a perm rating greater than 10 is highly permeable and not considered to be a vapor retarder.

What are the different type of Crawl space Vapor Barriers?

Reinforced Polyethylene Vapor Barriers

The first type and the most popular crawl space vapor barrier is the reinforced polyethylene plastic film. This engineered plastic film is the most widely used and the most durable, offering the longest service life and dollar for dollar your best value. This of course assumes the vapor barrier is made to high quality standards.

Unreinforced Polyethylene Vapor Barriers 12 Mil +

This product can be considered a vapor barrier, but most often it is a vapor retarder (see the difference here). The reason is because the center is woven polyethylene ribbons (like a tarp) and then coated with a thin, 2 mil, layer of clear polyethylene on both sides. The woven ribbons make this product extremely strong, but one scrap by a sharp rock and the outer layer of film is compromised.

Coated Woven Crawl Space Liners

As the name implies, this vapor barrier is made from polyethylene as well, but manufactured without the string reinforcement. This product is less durable in a crawl space environment, but does very well in a basement as a wall vapor barrier. Because it is less durable does not mean it cannot be used in a crawl space, because it can. You just have to understand that it cannot prevent tearing like the reinforced vapor barrier can.

Plasticized Aluminum Liners

This type of product is new to the crawl space scene. It is a mixture of a thin coated woven liner(3 Mil including the outer layers on one side), open cell foam(center) and a plastic film with some aluminum mixed in (1.5 Mil on the second side). This product boasts 0 perm rating because of the “aluminum” layer, but the reality seems to be far from that. Even if this product was a 0 perm, the installation would not be. I mean the 0 perm would be compromised with the tape seams, supports, and workmanship. Even if we allowed this products only claim to fame (0 perm) its very thin outer layers would prevent this product from performing due to its very low durability.

Why purchase your crawlspace liner from Americover® and not your local hardware store?

Americover’s crawlspace vapor barriers and liners are manufactured in America with virgin resins and uv inhibitors, if installed properly it should last up to 20 years or more. Purchasing at your local hardware store may be less expensive and more convenient, but it is likely to be compounded mostly of recycled resins containing a lot of debris and contamination which can cause off gassing, as well as shorten the lifespan of the liner causing it to degrade much faster, and requiring it to be replaced much sooner than anticipated. For more information on Virgin poly vs Regrind visit our Blog.

Which Mil Thickness is right for Your Crawl Space?

6 mil is the standard recommendation, but we advise you take into consideration the conditions of the ground and if you plan to utilize this space for anything. The diagram below will help you get an idea of which mil thickness is best for your crawl space.

Crawl Space Caliper
6 mil white crawl space liner

6 mil Reinforced vapor barriers are an economical choice when the overriding concern is cost. 6 milis not recommended for areas where there will be any activity, this is simply to keep moisture and gases from entering the crawl space.

Soil Compatibility:

Clay, Sand, Dirt, and mud without rocks or sharp objects.

10 mil clear crawlspace liner

10 mil Clear, reinforced vapor barrier is an economical resin that performs much better on the walls of a foundation, and can be used on the ground when there will be no activity taking place in the crawl space.

Soil Compatibility:

Clay, Sand, Dirt, and Mud without Rocks or Sharp objects.

8 and 12 mil black and white crawl space liner

8 mil Black/White, reinforced vapor barriers are frequently used on the walls with the 12 mil Black/White or 20 mil white liner on the floors. When installed in this manner, these vapor barriers are great protection to use the crawl space as a root cellar or for storage.

Soil Compatibility:

Clay, Sand, Dirt, Mud, Rocky Soil with tree roots and slightly larger rocks

12 mil antimicrobial crawl space liner

12 mil Antimicrobial, reinforced vapor barriers have antimicrobial additives that prevent the growth of harmful bacteria, fungi mold, and algae on or around the liner. 12 mil antimicrobial is suitable for the walls and ground of your crawl space for use as a root cellar or for storage.

Soil Compatibility:

Clay, Sand, Dirt, Mud, Rocky soil or soil with tree roots, and slightly larger rocks

20 mil white reinforced crawlspace liner

20 mil White, Reinforced vapor barrier is great for commercial applications where a heavy duty liner is required. This is the thickest crawl space liner with the highest puncture resistance rating we offer. It is white on both sides and provides a clean bright white finish to any crawl space.

Soil Compatibility:

Clay, Sand, Dirt, Mud, Rocky soil or soil with tree roots, large rocks and broken concrete.

How much Vapor Barrier will you need to Encapsulate your Crawlspace?

Standard mil recommendations

To measure your crawl space for a vapor barrier you will need to take the following measurements:

• Length of Crawlspace

• Width of Crawlspace

• Height of the foundation walls, or as high up on the walls you are going to encapsulation

• Perimeter Length of the entire space (length + width) multiplied by 2.

Since most crawlspaces are less than 4′ tall, using a 4′ or 6′ wide vapor barrier for the walls will keep the seams to a minimum.

How to Calculate Square Footage:

Americover’s crawlspace vapor barriers and liners are manufactured in America with virgin resins and uv inhibitors, if installed properly it should last up to 20 years or more. Purchasing at your local hardware store may be less expensive and more convenient, but it is likely to be compounded mostly of recycled resins containing a lot of debris and contamination which can cause off gassing, as well as shorten the lifespan of the liner causing it to degrade much faster, and requiring it to be replaced much sooner than anticipated. For more information on Virgin poly vs Regrind visit our Blog.

Floor and wall square footage

How much tape will you need for your crawlspace?

Vapor bond tape for crawl space encapsulation

Vapor Bond Tape

The general rule of thumb for Vapor tape is 1 roll per every 1000 square feet of vapor barrier. This amount can increase if there are a lot of piers or support columns. Vapor Tape bonds to most surfaces over a wide range of temperatures creating a waterproof seal and a clean appearance to the crawl space encapsulation.

Tip: Keep the tape in room temperature until ready to use. Cold temps harden the adhesive making it difficult to stick

Roll size is 4″ x 180′

Butyl tape double-sided reinforced rubber tape

Butyl Tape

The amount you need is based on the Permieter Length of the entire space. Butyl Tape is a double-sided aggressive reinforced butyl rubber tape used to seal the vapor barrier to foundation walls. Butyl is non-hardening and flexible to provide a waterproof seal. It can also be used to join panels of vapor barrier together by overlapping the seams and applying the tape in between the layers.

Roll size is 1.5″ x 100′

Christmas tree ratchet fasteners for vapor barrier

Christmas Tree Ratchet Fasteners

Christmas Tree Fasteners are used to attach the vapor barrier to the foundation wall. These fasteners are made of heavy duty nylon and are 5/16″ diameter x 1-1/8″ long and are inserted into a 5/16″ hole (a hammer drill work best). They are to be installed every 18″ – 24″. The fasteners have a flat white head and a conical tip. This gives them a clean, unobtrusive look after installation. These pins come in packs of 100 and 500 pieces and are required to carry the weight of the vapor barrier on the foundation wall.

How to Install a Crawlspace Liner

Americover’s crawlspace vapor barriers and liners are manufactured in America with virgin resins and uv inhibitors, if installed properly it should last up to 20 years or more. Purchasing at your local hardware store may be less expensive and more convenient, but it is likely to be compounded mostly of recycled resins containing a lot of debris and contamination which can cause off gassing, as well as shorten the lifespan of the liner causing it to degrade much faster, and requiring it to be replaced much sooner than anticipated. For more information on Virgin poly vs Regrind visit our Blog.

1. Cut the Vapor Barrier to size. The vapor barrier liner comes folded and rolled on a core. It is easier to cut and size the liner material before you take it into the crawlspace. After the material is cut to size roll it up (white side on the inside) so when you unroll it in your crawlspace it stays clean.

     a. To cut the Floor Pieces, measure and cut a piece of vapor barrier liner material wide enough to cover the floor from the wall to the 1st line of piers or support then proceed to measure and cut the remaining floor pieces.

          i. IMPORTANT: Don’t forget to measure enough material to seal an overlap of 6-12 inches on the wall pieces and pieces beside it.

     b. For the Wall, keep the seams to a minimum by using a 4 ft or 6ft wide vapor barrier, since most crawlspaces are less than 4′ tall.

2. Start with the walls. To attach the liner, apply the 2 sided butyl tape 4 inches – 6 inches down from the top of the wall or sill plate. (This is to leave a space for pest inspection). *Do not remove the release liner on the exposed side of the tape until you are ready to attach the liner. (It may be easier to first apply the butyl tape to the vapor barrier, and remove the release liner as you are applying it to the wall.) otherwise, remove the release paper from the butyl tape in about 4 feet – 6 feet increments.

3. Fasten the Liner with some type of permanent fastener every 24 – 30 inches. The fasteners should go through both the material and the butyl tape. This can be accomplished by one of the following methods:

     a. Use a Hilti

     b. Use a Ramset Powder Fastener

     c. Drill a 5/16″ hole and press in our Christmas Tree Ratchet Fasteners

4. Installing Vapor Barrier on the Floor. Starting at the piers or support posts, cut and notch the vapor barrier on both sides of the support about 6-12 inches above the ground. Wrap the vapor barrier to fit tightly around the support, and use the 4 inch white Vapor Tape to seal the material.

5. Smooth the liner out from the supports to the wall and tape the seams with the 4″ White Vapor Tape.

     a. Overlap the Seams 6 inches to 12 inches.

     b. You may remove your footwear or use disposable shoe covers to keep the vapor barrier liner clean.

We hope these tips guide you through installing your Crawl space vapor barrier liner. One of our past customers made some incredibly informational videos we believe will help you get a better understanding of how to install your liner. Those videos are below. For more information please contact our representatives at 800-747-6095.

Crawlspace How-to Videos

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