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.) 

Cover sump pump wells or pits with an airtight cover that allows for all necessary penetrations to be tightly sealed 

Install sump pump covers to allow bulk moisture to drain from above the cover utilizing trapped or one-way ball valve fittings, or equivalent 

Seal around the perimeter of all drain fittings that penetrate a concrete slab using urethane caulk or equivalent sealing material

Sealant must not affect the ability of the drain to function and be compatible with the surfaces it contacts

Install a one way valve in all untrapped, below grade drain fittings that does not interfere with appropriate drain function 

Resources: https://drive.google.com/drive/folders/1qa5Dk5fzzIKLQp0Ex5Fy3EOm1oaRdgks?usp=share_link