GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Radon Mitigation and Vapor Barriers Under Slab

user-6445625 | Posted in General Questions on

Hey folks, does anyone have an opinion about the thickness or spec for our under-slab vapor barrier for radon mitigation? Trying to decide between 15 and 20 mil. thanks

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. plumb_bob | | #1

    Either will work if detail correctly. Remember that it is not just a vapour barrier, but also an air barrier, and must be detailed as air tight around all penetrations. Frequent areas of concern are around sumps and at the slab perimeter.

    If drain rock is installed between the ground and the poly, the thicker poly will stand up better to damage during construction.

    1. user-6445625 | | #2

      thank you bob!

  2. Expert Member
    Michael Maines | | #3

    If it's going to be covered with a concrete slab, I think 15 mil is more than enough. I spec 10 mil.

  3. JeffWilliams56 | | #4


  4. abramsjey34 | | #5

    Thanks a lot

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |