Cob and ICFs?

Hi all!
My husband and I are starting to build our home this summer, and after many many rounds of planning, discussion, and compromise I believe we've settled on ICF exterior walls with cob interior walls. We're building in northern MN, so the insulation of ICFs is necessary, but I want as much thermal mass as I can get.

I have two questions- Is there anything special I'd need to do to build interior cob walls on a concrete slab? Can they go directly on the slab with nothing between?
And also, how feasible is it to plaster the inner walls of the ICFs with cob? So instead of insulation facing the inside of the house I'm hoping to coat them with 6 inches or so of cob and gain thermal mass that way as well.

It's been a lot of talk and we've run the gamut of options but this is the year we build and I'm so excited!

This may be a good topic to read;
https://permies.com/t/211819/Straw-bale-Eastern-Oklahoma-Hot

As a Civil Engineer, I have to point out a few points;
- slab would normally be thickened under cob walls
- Nothing needs to be under the cob, but it is a good idea to lat a row of fired bricks to create a hard architrave to protect the cob.
- Can you make earth bricks and lay them next to the external walls and then plaster them?
- furniture can be cob

John C Daley wrote:This may be a good topic to read;
https://permies.com/t/211819/Straw-bale-Eastern-Oklahoma-Hot

As a Civil Engineer, I have to point out a few points;
- slab would normally be thickened under cob walls
- Nothing needs to be under the cob, but it is a good idea to lat a row of fired bricks to create a hard architrave to protect the cob.
- Can you make earth bricks and lay them next to the external walls and then plaster them?
- furniture can be cob

Earth bricks are a great idea!
Yeah, I plan on making the furniture from cob, and then also a large batch RMH stationed in the sun from south facing windows. I'm not sure how much mass is needed for passive solar, I'm just running on the theory that more is better lol

I would suggest a physical tie in from your ICF wall interiors to the cob. ICF usually have attachment points which are crossmembers at 16 inches on center to coincide with modern/“normal” building approaches and materials. These can be used to attach anchors and lathe or chicken wire that will grab the mud cob and physically hold it to the wall. Great idea, and I hope you keep us updated here! Have fun with it..