A vapor barrier is a crucial material for building projects under concrete slabs, in crawl spaces, for gas and radon mitigation, for mold barriers, and for other uses.
Vapor barriers are valuable tools when used properly because of their low permeability, but vapor barriers are not meant for every use case. Builders and contractors should always refer to their local building code requirements when determining whether they need a vapor barrier and what type.
What Not to Do with a Vapor Barrier
Don’t: Use a Vapor Barrier to Waterproof a Failing Concrete Basement Wall
Because a vapor barrier is a low permeable barrier, it keeps moisture from passing through. This is beneficial to keep moisture away from a dry surface but will trap moisture behind it if installed on a water-damaged concrete wall, causing the wall to fail further. The failure should be rectified before installing a vapor barrier. If the failure is caused by a leaking water source, the source of the leak should be repaired.
Don’t: Use a Vapor Barrier as an Underlayment without Consulting the Flooring Manufacturer First
Underlayment is a non-negotiable part of a laminate flooring project, and vapor barriers make suitable underlayments as they protect the flooring from moisture and rot. Most flooring warranties, however, become void if you don’t use the recommended products by the flooring manufacturer. Be sure to consult the manufacturer before installing the underlayment.
Don’t: Staple or Nail a Vapor Barrier without Using Proper Tapes
Vapor barriers are not meant to be punctured. Once the vapor barrier has been punctured, it jeopardizes the integrity of the liner. Many vapor barriers are difficult to puncture and will uphold their resistance through heavy installation and use. To install a vapor barrier, tapes like butyl tape and vapor tape can be used to properly seal the vapor barrier and prevent failure.
Don’t: Use a 6 mil Vapor Barrier in a Crawl Space Used for Storage.
For areas where there will be a lot of foot traffic or where you plan to store stuff, the vapor barrier should be thicker than 6 mils. Consider using an 8 mil – 20 mil vapor barrier, like Americover’s Pro Crawl Anti-Mold Vapor Barrier with MPT ™, to prevent damage to the sheeting.
Don’t: Put a Vapor Barrier on the Bottom of the Floor Joist in the Crawl Space.
Because vapor barriers are good at retaining moisture, putting plastic sheeting on the joists can cause moisture to build up under the floor. Crawl Space vapor barriers should instead be overlapped on the ground to keep away humidity, gasses, and radon in the ground.
Don’t: Assume You Need a Vapor Barrier
Proper use of a vapor barrier means evaluating whether one should be used. Builders and contractors should consult vapor barrier experts to understand when one should be used, how thick the vapor barrier should be, and how to properly install it. Americover has a team of leading experts with decades of experience.
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