Soil-Gas Retarder

Detail ID 2.0401.1
Topic
Radon
Subtopic
Radon Precautionary Measures
Desired Outcome

Reduce potential for radon to enter living space through exposed soil in subspaces

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

Specifications

  • SF
  • MF
Specification Objective

This detail applies when installing soil-gas retarders over bare earth for the purpose of limiting radon intrusion into a building space

Apply correct details

  • SF
  • MF
Specification Objective

Remove all vegetation and organic material from area to be covered

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

Prevent soil-gas retarder damage

  • SF
  • MF
Specification Objective

Select flexible membranes that are a minimum of 6 mil (0.15-mm) polyethylene or equivalent flexible material

3 mil (0.08-mm) thickness is permitted if a cross-laminated product is selected

When the space is used for storage or entry is required for maintenance of utilities; heavier gauge sheeting or a protective covering (such as rubber roofing membrane) shall be installed in these areas

Select appropriate and durable material for all spaces

  • SF
  • MF
Specification Objective

For Unvented/Conditioned Spaces:

Cover any under-floor area not covered with poured concrete

Cover any air permeable foundation wall or pier material, such as hollow core block

Do not install in contact with non-treated structural wood

For Vented/Unconditioned Spaces:

Cover any under-floor area not covered with poured concrete

Do not install in contact with non-treated structural wood

Complete coverage of permeable foundation surfaces without compromising wooden foundation material

  • SF
  • MF
Specification Objective

Maintain a 3" inspection gap between the top of the soil-gas retarder and any wood if local codes require

Allow for termite inspection

  • SF
  • MF
Specification Objective

Overlap seams a minimum of 12" with reverse or upslope lapping technique and seal all seams with a durable, compatible sealant

Durably sealed seams

  • SF
  • MF
Specification Objective

Extend soil-gas retarder a minimum of 6" up all non air-permeable foundation walls and piers. (i.e., solid core block, brick, or poured concrete)

Seal it to all foundation walls and piers with a compatible material that creates an airtight, durable seal

Use mechanical foundation connections where feasible

Do not install in contact with non-treated structural wood

Extend soil-gas retarder over all air-permeable foundation walls or piers (i.e., hollow core block, brick, or rubble) except for required termite inspection gap

Do not install in contact with non-treated structural wood

Cover all potential entry points of radon with soil-gas retarder without compromising wooden foundation material

  • SF
  • MF
Specification Objective

Seal all necessary penetrations in the soil-gas retarder with compatible materials using a lapped-patching technique that assures a tight-fitting seal

Restrict soil-gas intrusion through penetrations

  • SF
  • MF
Specification Objective

Do not install stakes to secure soil-gas retarders

Install ballasts or weights to secure it on the ground where movement is likely with ballast materials that are smooth and free from protrusions

Restrict movement or uplift of the barrier without damaging soil-gas retarders

  • SF
  • MF
Specification Objective

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

Prevent water accumulation above or below the barrier

Next Detail:
Sump Well/Pit Covers