the elements of a proper foundation are neccessary for the protection of the building. to effectively do this there needs to be in place ,
1. Drainage. Drain the first few inches of soil as well as drain water that will effect the base of the foundation (the footer or peer). drainage also need to incorporate a plan for removing water that is shed from the roof. Drainage would also include moisture under the floor taken to the sump or day lighted outside the subsurface drain. so effectively 4 drains or 4 areas to drain.
2. the actual foundation. my home is a post and beam with straw bale infill. my foundation is both a rubble foundation with a bond beam that supports the straw bales and peers on the inside of the house supporting the structure of the house. I used concrete for the peers. this is what i knew how to do. im not sure what alternatives there are for concrete peers that incorporates both the downward pressure of the posts and roof and also the upward pressure of wind or updraft. think tornadoes. the peers are 2 feet deep, frost here is 18 inches this is to code. I only used sonatube above the excavated ground level. i used metal post bases to attach the peer to the posts. the peer also rises to the finished floor level. i narrowed the last 2 inches of the peer down to 6 inch. the straw bale foundation is a 2 foot deep 18 inch wide rubble trench with a 4 inch french drain under the rubble that drains to daylight about 20 feet way well below the base of my foundation grade. the edges are lined with silt screen and filled with gravel. on the top of the foundation is a concrete bond beam 4 inch think and on top of this beam is 2 2x4 pressure treated wood strips that the bales sit on. these are there to separate the concrete from the bales. I now know there are alternatives to concrete however im not sure how to implement them. the top of the concrete bond beam sits at my finished floor grade and is 4 inches above the outside grade.
3. The roof. my roof has 3 foot over hanging eaves. this worked very well as i had exposed bales for over a year and had no water on the even though i get 60 inches a year here. with gutters draining off and tying into the sub surface level french drain. the subsurface drain is just under the outer edge of the house eaves and just under the gravel walkway i have around the house. this drain daylights also 20 feet away from the house. and finally the subfloor drain drains into the foundation drain. to do this i tapered the subfloor under my sub gravel so it drains to the back of my house.
This may not be perfect however i use current engineering standards to mix my concrete and to sized my peers. i also made sure i met frost standards for my area and new the local soil standards.