Un-Vented Subspaces - Ground Cover

Detail ID 2.0202.1
Topic
Moisture
Subtopic
Ground Vapor Retarders
Desired Outcome

Minimize ground moisture vapor and soil gas with a durable, effective vapor retarder

SF Single Family Site-Built Housing
MH Manufactured Housing
MF Multifamily Housing

Specifications

  • SF
  • MH
  • MF
Specification Objective

Remove all vegetation and organic material from area to be covered

Remove all debris that can cause injury or puncture ground vapor retarder (e.g., nails, glass, sheet metal screws, etc.)

Minimize punctures

  • SF
  • MH
  • MF
Specification Objective

Select a 6-mil minimum ground vapor retarder of 0.1 perm or less

Durable material selected

  • SF
  • MH
  • MF
Specification Objective

Cover all exposed soil

Extend ground vapor retarder a minimum of 6" up all foundation walls and piers, but do not install in contact with non-treated structural wood

Create a continuous ground vapor retarder layer that does not compromise wooden foundation materials

  • SF
  • MH
  • MF
Specification Objective

The ground vapor retarder will not interfere with the established drainage pattern (e.g., to sump pits, French drains, etc.)

Ensure proper drainage

  • SF
  • MH
  • MF
Specification Objective

Overlap seams a minimum of 12" with reverse or upslope lapping technique

For wall to floor connection, install the wall vapor retarder under the ground vapor retarder

Seal all seams and connections to foundations and piers air tight with a durable, compatible, sealant

Mechanically attach ground vapor retarder to foundation and piers where practical

Provide airtight seal for ground vapor retarder

  • SF
  • MH
  • MF
Specification Objective

Fasten ground vapor retarder to ground with durable fasteners or ballast(s) when installed on sloping ground, or space is accessed for routine maintenance or storage

Prevent movement and uplift of the air barrier and ground moisture barrier

  • SF
  • MH
  • MF
Specification Objective

Seal all penetrations in the ground vapor retarder with a compatible sealant

Ensure ground vapor retarder is air tight

  • SF
  • MH
  • MF
Specification Objective

Install a durable (minimum of 10-year service life), easily seen sign, sized a minimum of 8.5"x 11" at each access to the space

Sign shall minimally include the following items:

Warning to prohibit storage of hazardous and flammable materials

Caution not to damage the ground vapor retarder, air barrier, insulation, and mechanical components specific to the space

Immediate repairs are needed in the case of damage

Provide essential safety and maintenance information