Frost-protected slab on a moderate slope
I’ve been reading through the “Revised Builder’s Guide to Frost Protected Shallow Foundations” (http://cdnassets.hw.net/10/9d/3808b4b94676968c59b8548815f3/revisedfpsfguide.pdf) 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 Detail Library
A collection of one thousand construction details organized by climate and house part
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?
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.
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.