How to Install a Residential Vapor Barrier

Written by m deehn
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The intent of a vapour barrier is to impede water permeation of a structure. Although it may not be considered the most important moisture control method used in your home, the installation of a vapour barrier an advantageous addition to any insulating and weatherization program. Not to be confused with "house wrap," most vapour barriers are installed on the interior of the residence during construction or renovation.

Skill level:

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Things you need

  • Polythene plastic (vapour barrier material)
  • Staple gun or tacker
  • Staples
  • Seam tape
  • Utility knife

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  1. 1

    Insulate the walls in accordance with the manufacturer's recommendations and local code (if not in place). Caulk or use spray-in insulation to seal small gaps or cracks around windows, utility boxes and in corners.

  2. 2

    Cut a piece of vapour barrier the height of the wall plus several inches. Starting at one side of the room, attach the barrier to the top plate and secure with staples. Use a powered staple gun or manual stapling hammer to ease the process.

  3. 3

    Allow the vapour barrier to drape from the top plate. Smooth with one hand while using the other to place staples to secure. The barrier should lay flat against the wall studs without any wrinkles or folds that may trap moisture.

  4. 4

    Continue to hang the barrier on the wall a piece at a time until it is completely covered. Try to have pieces meet over a stud when possible. Allow for a 2- to 4-inch overlap at all seams and corners.

  5. 5

    Apply vapour barrier tape to each seam. Use a seam tape product that is recommended by the manufacturer. Trim off any excess barrier at the top or bottom of the wall as well as around any electrical boxes or HVAC accesses with a utility knife.

Tips and warnings

  • Ask your builder if one is necessary for your home.
  • For finished homes, consider a vapour barrier paint product.
  • Note that not every home should install additional vapour barriers.
  • If your insulation has a vapour barrier, check before installing a second vapour barrier.
  • The improper use of a vapour barrier can cause moisture problems.
  • Use caution with powered staplers.

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