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Building Basics
House is Wrapped in Vapor Barrier: Drainage Plane Behind Exterior Wall Cladding


After the roof assembly is completed, a water-resistant barrier should cover the entire house and the seams should be taped to provide a complete drainage system.


When some moisture gets past the siding, a wall water barrier provides a path for it to safely drain down and away from the wall and gives the home comprehensive moisture protection.


This barrier can be one of the following:

  • Housewrap that is lapped shingle-style
  • Water-resistant rigid foam insulation that is taped or sealed at all seams
  • A wet-applied moisture-resistant coating
  • Other water-resistive barrier materials that are recognized by the ICC-ES or another accredited agency.

The water barrier must be thoroughly sealed and flashed at:

  • All exterior wall openings and penetrations (e.g., windows, doors, water spigots, exhaust vent outlets, HVAC condensate lines, light fixtures, and receptacles)
  • All wall intersections (e.g., roofs, foundations, and other transitions).