How to Install a Vapor Barrier Joist

Written by louis gutierrez
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How to Install a Vapor Barrier Joist
The vapour barrier protects the plywood on the roof from inside moisture. (roof trusses inside house image by adrian fortune from

Installing a vapour barrier to a ceiling joist can help prevent moisture inside the house from getting inside the attic and damaging the roof framing and insulation. The vapour barriers are most commonly used in wooden homes but are more recently being used in all homes for increased energy efficiency. The vapour barrier is a paperlike barrier that is secured to the framing of a house.

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Things you need

  • Vapour barrier
  • Utility knife
  • Staple gun
  • Construction tape

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  1. 1

    Roll the vapour barrier out from one wall to the other wall and cut it with the utility knife.

  2. 2

    Secure one end of the vapour barrier to the ceiling joist. Use your staple gun to staple the vapour barrier to the ceiling joist.

  3. 3

    Work your way back to the other end of the wall stapling the vapour barrier every 8 inches. Smooth out the vapour barrier with your hands as you work your way back.

  4. 4

    Cover all the staples, the edge of the vapour barrier where it meets the wall, and all connections with the construction tape. The tape will make an airtight seal.

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