GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter 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

Where does insulation fit in below grade waterproofing?

noaway | Posted in General Questions on


I am aiming to waterproof and insulate some below grade concrete footings I am trying to understand where to orient the dimple mat in relation to the insulation. Is this right or should the dimple mat be in between the concrete and the insulation? I am right on the edge of 6b and 7b.

I have also seen Type-II EPS recommended as below grade insulation. Are there any preferred products to fill this role? 

Many 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. Expert Member
  2. noaway | | #2

    Thank you @Michael!! I got an account to read your articles and I have a few followup questions if you don't mind. I reuploaded the image but I see now I should add a flashing at grade and not just at the top.

    As far as the flashings - do you have a strong feeling about what kind to use? Would something like this be sufficient if it covers both the dimple mat and the exterior insulation? ( Or would it be better to choose a system that has a purpose made trim for this purpose? The polywall system I was looking at doesn't seem to offer a top trim.

    Prior to your articles I was only aware of Polywall's system for this but I see now there are many systems on the market. Do you recommend any of these systems over the rest?

    What kind of insulation would you recommend for this purpose? I have seen that Roxul comfortboard has an approved product for below grade application and I like that for it's fire resistance but people on this forum seem to prefer Type-II EPS for it's compressive strength. I am having trouble finding Type-II EPS near me though but I might not be looking in the right places. Do you have any recommendations?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |