Seam tape, is it necessary to use it to encapsulate your crawl space? What purpose does it serve? Why do so many contractors not install it or install the wrong type or incorrectly? Does code require you to use seam tape in the crawl space? Can't you just use duct tape?

These are some of the questions we have heard over the years from frustrated homeowners that are tired of the bad information they are getting from their the crawl space encapsulation contractors.

What is Seam Tape?

Encapsulation seam tape, also called seam sealing tape, is used in the sewing industry but we are going to focus on how we use it in the crawl space encapsulation industry. Seam tape is waterproof tape that is used to seal together vapor barrier (crawl space plastic) at the cut joints when the vapor barrier is installed.

Seam tape can also be used to seal punctures made by gravel or sharp objects as well as fix cuts made in the crawl space plastic.

Typically seam tape is white but comes in different colors. It also comes in various thicknesses and lengths but we recommend using a 4-inch seam tape for best coverage when joining vapor barrier together. Seam tape can be purchased online for crawl space encapsulation DIYers.

Encapsulation seam tape image

Seam Tape vs Duct Tape

As mentioned above crawl space encapsulation seam tape is different from duct tape. There are wide varieties of duct tapes available so for this purpose I am referring to the kind typically found in hardware stores and other retail outlets.

Duct tape is usually not as wide, 1.88 inches, and easier to break or rip while seam tape is usually 4-inches and good tapes are cut versus tearing them. Seam tapes we recommend are 9-mil thick and duct tapes are 7-mil.

Duct tapes are less expensive and usually made with fabric. Seam tapes are made with polyethylene. This is why seam tapes are waterproof and duct tapes are not. Seam tapes usually have superior adhesive capabilities versus duct tapes. The last thing you want is after hours of taping, it start coming loose.

Seam Tape and Basement Waterproofing

Seam tapes tend to be more pleasing to the eye than duct tapes and can also be used in basement waterproofing. When used in basement waterproofing, generally seam tape is applied to waterproofing panels or vapor barrier that is attached to the basement wall.

Seam Tape and Building Code

This can depend on what part of the country you live in and of course interpretation of the codes enforcement inspector but if you close your crawls pace, vapor barriers are required to be overlapped and taped. If the vapor barrier was installed and not taped and you close the crawl space, this could cause your crawl space to be out of code.

They don't specify what type of tape you must use but for us the code is pretty clear that taping the vapor barrier is a necessity in performing crawl space encapsulation correctly.

Seam Tape and Humidity

Seam tape functions in the same way the vapor barrier or vapor retarder functions by keeping the ground water from evaporating into the crawl space. This is why a properly installed vapor barrier with seam tape is a vital step in controlling humidity. Installing a dehumidifier is always recommended in damp environments too.

Encapsulation Contractors and Seam Tape

Based on all the facts we have laid out we are not sure why some crawl space encapsulation professionals choose to ignore the importance of encapsulation seam tape. For us the reasons are clear why the vapor barrier should be overlapped and taped with a great waterproofing seam tape.

If you'd like an estimate on your crawl space encapsulation, basement waterproofing, attic insulation, yard drainage or duct sealing and cleaning, please contact us today.

We hope you will let us know your thoughts on seam tape in the comments below. Do you feel it is essential to crawl space encapsulation or do you have other recommendations? Thanks for reading.

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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.

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