What is the minimum thickness for vapor retarders used in basements?

The minimum thickness for vapor retarders used in basements is typically required to be 6 mil. This standard is established to effectively inhibit the passage of moisture vapor, which can lead to various issues such as mold growth, structural damage, and degradation of building materials. A vapor retarder with a thickness of 6 mil strikes a balance between being durable and effective while remaining manageable for installation.

Thicker vapor retarders, though they may offer slightly better performance, are not generally necessary or mandated by code for standard residential applications. The 6 mil thickness is adequate for most conditions encountered in basements, provided that the installation is done properly and other moisture control measures are also in place. Therefore, this specification is widely accepted and utilized in building codes and best practices for residential construction.