Moisture barriers should have overlapping layers of what thickness of polyethylene?

The recommended thickness for overlapping layers of polyethylene used as moisture barriers is indeed in the range of 4-6 mil. This thickness is appropriate because it provides a suitable balance of strength and flexibility needed to effectively block moisture.

Using a thickness of 4-6 mil ensures that the material is durable enough to resist punctures and tears during installation and throughout its service life. This level of thickness is also effective in creating an impermeable barrier against moisture, which is crucial for preventing water vapor from penetrating into spaces where it could cause damage, such as in basements and crawl spaces.

In contrast, thinner materials may not offer the same level of protection and could easily be damaged, while thicker materials can become cumbersome to work with and may not expand or contract adequately with temperature changes. Therefore, the 4-6 mil thickness is widely accepted in the industry for moisture barrier applications, ensuring an effective shield against moisture ingress while remaining manageable for installation.