How Is a Polyethelene Vapor Barrier Seamed?

Polyethelene (poly) is the most commonly used air and vapor barrier in modern construction. Its popularity is due to its low cost and ease of installation. For residential construction, use 6-mil poly to create the vapor barrier. The 6-mil, which is 6/1000 of an inch, refers to the thickness of the material. Installing a vapor barrier requires special attention to the seams to assure it is as air tight as possible. Joining two sheets of poly is simple once you understand the steps.

Things You'll Need

• Vapor barrier tape
• Acoustic sealant
• Caulking gun

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Instructions

1. • 1

     Overlap the two sections of polyethelene vapor barrier approximately 6 to 8 inches.

   • 2

     Use a caulking gun to apply a solid bead of acoustic sealant in the center of where the two sheet overlap, running from edge to edge.

   • 3

     Push down the top sheet and press along the acoustic sealant, joining the two sheets together.

   • 4

     Apply vapor barrier tape from the top to the bottom along the leading edge of the top sheet joining the two together. This creates a double barrier against air and moisture penetration.