I was hoping to get some feedback on a foundation I am planning to start in the next few days. We have a 30ft yurt coming in about a month, we hope to use the yurt to get ourselves going on the property, but eventually repurpose the fabrics and transition to home to be straw bale/cob. The yurt will have an earthen floor inside.
While yurts are typically build on wood decks over piers, or on a concrete slab, financially a wood deck is not an option for us and I want to avoid concrete as much as I reasonably can. The place we purchased the yurt from provides foundation diagrams, one of which is for a concrete slab which I added as an attachment.
Here is a sketch of what I was hoping to build -->
Imgur: Proposed Yurt Foundation
...but I had a few questions/concerns; Blue Ridge Yurts concrete diagram shows an overhand of concrete on their version of a concrete slab where the yurt attaches to the foundation via tapcon screws, my sketch also has this overhang but I am concerned about the weightbearing capacity of an overhang like this. If a 3" layer of concrete overhangs the wall by 2 inches, where the yurt wall itself is made of lattice and 2x4's, nearly half the wall will rest on this overhang. I would think if the yurt place thinks an overhang is safe, then it must be safe? But they also use a complete slab so I'm not sure..
My version of this foundation includes rigid foam sitting under the overhang to try to create a frost protected version of the slab. I am in Maine and our frost line is 4ft down, however I don't believe we could get 4ft down without having to break through a lot of ledge. We are sitting on solid rock that goes hundreds of feet below us, the soil on top is fairly shallow. This was my motivation to frost protect. To decrease the likelihood of water being trapped under our foundation and freezing/thawing over and over, I thought we should add a rubble trench like region underneath the walls.
I suppose my main concerns are; 1. Will the overhang be strong enough to bear the weight of the walls? Or should I chuck the overhang idea, have the walls sit directly on the stem wall, and just stick rigid foam around it more awkwardly?, and 2. Should I have some form of rebar, J hooked into the bottom plate of concrete, going up through the mortared stone, and J hooked again through the top plate of concrete, in order to better anchor the foundation? We are on the peak of a large hill, in a relatively flat old farm field. We have yet to be there for a winter but the neighbors have told us about some crazy strong wind. I do not want our house flying away during a storm.
Thanks for any ideas or feedback!