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

Insulating the Interior of Poured Basement Walls

user-4405197 | Posted in Building Code Questions on

This picture is from building and shows an ICF foundation with insulation under the slab. My question relates to the interior wall plane where the floor slab meets it. Does the code require that the slab make physical contact with the concrete wall? If it does, how do code officials deal with situations like this one with ICF foundations? I wanted to have a similar insulation setup on the interior with poured walls. Prior to pouring the floor I would lay rigid foam along the ground and up the wall – thermally isolating the slab. Would the vapor retarder on top of the floor foam be wrapped part way up the wall prior to pouring the floor? Any thoughts on this would be appreciated. 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. user-4405197 | | #1

    Here's the attachment from my post above.

  2. user-4405197 | | #2

    Also, does the capillary break between the footing and the wall get lined with the same WRB that is wrapped or sprayed on the exterior of the wall?

  3. ohioandy | | #3

    Code does not require contact between slab and wall. Thermal isolation of the slab edge as shown in the BSC detail is important, but it doesn't show the critical detail of the vapor retarder. Yes, the poly sheet should be lapped up the foundation wall a ways, and made airtight with sealant before applying the wall insulation. This is best practice for preventing radon entry at the slab edge. After the floor is poured, the crack between it and the wall insulation should also be caulked for the same reason.

  4. Expert Member

    I'm not that familiar with your codes, but the IRC does appear to have lateral support requirements for foundation walls. Maybe someone can chime in on how they work.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |