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Fastening Plastic Vapor Barrier in Your Crawlspace

crawlspace vapor barrier diagram We received a call from John in Ohio who is installing his own crawlspace vapor barrior and was not sure how to fasten it to the walls.  Do you know the easiest way to fasten your plastic vapor barrier so that it works properly?

We found several solutions to this problem.  Click the diagram on the right to see the ideal positioning of the moisture barrier.

Crawlspace Vapor Barrier Instructional VideoHere is a vapor barrier movie showing you how to stake down the plastic sheeting.  Notice, his moisture barrier does not go up the sides of the wall.   You will observe that in the video the vapor barrier only goes to the edge of the wall, while the picture shows the polyethylene being attached several feet up the wall.  Depending on your particular crawlspace and personal preferences, you can do it either way.  If you choose to go further up the wall however, be sure the wall is dry before attaching the plastic sheeting and be sure not to attach it to wood posts or studs because moisture will become trapped and then you have the potential for wood rot.

If needed, run your Dri-Crawlspace Dehumidifier® for a day or two to dry out the walls and surfaces before attempting to use tape or adhesives on the crawlspace walls.

The seams in your vapor barrier should overlap by 6 inches and be sealed with builder’s tape or construction adhesive to form an airtight barrier.  You can seal the edges of the vapor barrier to the foundation walls with construction adhesive.  When it is completed, weigh down your vapor barrier with sand or stones to help prevent ground moisture from escaping into the crawlspace and to help protect the polyethylene from tearing when walking on it.

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