How to Install a Polyethylene Vapor Barrier

Vapor Barrier on Walls

• 1

  Clean the room and vacuum before starting your installation. Remove anything from the room that you don't need for the installation.

• 2

  Caulk all joints in the room around windows, doors, outlets and seams in the wood.

• 3

  Cut pieces of vapor barrier to a size you can handle and install it on the walls starting at the ceiling. Allow it to come down to floor level and leave about 3 inches of overlap on the floor.

• 4

  Stretch the poly barrier to remove all wrinkles. Staple the top along the top edge near the ceiling. Continue to gently stretch the poly downward and staple every 2 feet along the room frame as you move downward. Don't concern yourself at this point about covering windows or outlets.

• 5

  Cut another piece and repeat installation, allowing the next piece to overlap on the frame to make it easier to seal.

• 6

  Cut out windows, doors and outlets after covering the entire room with poly barrier. Place sheathing tape along the edges to seal as you cut.

• 7

  Run a bead of caulk under the edge of poly in the corner where the walls meet the floor to seal at the floor level.

• 8

  Follow the same guidelines to line the ceiling, allowing about 4 to 6 inches of poly to hang down along the walls for sealing. Use tape to seal the pieces on the ceiling to avoid the mess that eventually results from using acoustical caulk.

• 9

  Add extra staples to prevent the poly barrier from sagging.

Vapor Barrier in a Crawl Space

• 10

  Install the poly barrier on the floor of your crawl space as described in Section 1. Lay the pieces of poly along the edge of the wall on the floor.

• 11

  Allow the vapor barrier to come up the sides of the wall a foot or two. It is not necessary to bring it up the wall and leaving it along the edge of the wall where it meets the floor is acceptable. If you do extend it up the wall, make sure the wall is dry before doing so.

• 12

  Overlap seams by about 6 inches. Seal them with the sheathing tape.

• 13

  Seal the edges to the wall with adhesive, and weight down the vapor barrier with stones or bags of sand, which helps prevent moisture from coming into the crawl space.