Soil-Gas Retarder

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

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.)

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

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

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

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

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

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

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

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