What is the minimum thickness of polyethylene sheeting that should be used as soil-gas retarders in crawl spaces?

The minimum thickness of polyethylene sheeting recommended for use as soil-gas retarders in crawl spaces is 6-mil. This specification is based on industry standards and practices aimed at effectively preventing the intrusion of radon gas and other soil gases into buildings. A 6-mil thickness is sufficient to create a barrier that resists the movement of gas while also being manageable in terms of installation and cost.

Using a polyethylene sheeting of at least 6-mil ensures that it is durable enough to withstand typical conditions found in crawl spaces, such as moisture and wear. Thicker materials, while potentially offering greater resistance, may not be necessary for effective radon mitigation and could increase costs unnecessarily. Therefore, the recommended minimum thickness provides a balance between performance and practicality.