It sounds like you are asking about a vapor barrier.
- A properly installed vapor barrier will prevent excessive moisture from entering your crawlspace through the ground or the foundation walls.
- We recommend a minimum of a 6-mil poly installed over 100% of the crawl floor with overlapping seams of 12" and continue the vapor barrier up the crawlspace walls until it is above the exterior grade.
For more information:
Check our basement moisture Q&A to see what other homeowners and contractors are saying about vapor barriers, insulating foundation walls, etc.