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

Frost-protected slab on a moderate slope

ethant | Posted in Green Building Techniques on

I’ve been reading through the “Revised Builder’s Guide to Frost Protected Shallow Foundations” ( and notice that they recommend FPSF on “low slope sites.” I’m assuming that this would preclude using on a site of about 15% slope, but not sure what is generally thought of as “low slope.” Any thoughts on FPSF on a 15% slope (Zone 5A), building is a split level with slab on grade, double stud walls with a concrete foundation wall serving as the uphill wall on the house and garage.

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. ethant | | #1

    I should add that my structural engineer kind of dismissed the whole concept of the Frost Protected Shallow Foundation out of hand, but I think he is just too busy to be bothered... perhaps I can find another structural engineer who can wrap his head around the concept and give me/us guidance?

  2. GBA Editor
    Martin Holladay | | #2

    As you guessed, the person to advise you in this instance is an engineer, not readers of an internet forum. Good luck.

    I will say that it's possible to install a frost-protected shallow foundation on a steep slope, because I've done it. That doesn't mean it's easy. Get the details right, or the foundation will fail. Your engineer is your friend.

  3. ethant | | #3

    Martin, thank you. My concern is that the structural engineer is very busy and from what I could gather, did not feel like working on anything that did not fit neatly into his computer modeling software... He first told me that I should modify the foundation layout even though we both knew it made sense because his software couldn't account for certain factors. So maybe I need to find a different engineer. It is surprisingly difficult, in a sea of architects, to find a structural engineer.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |