Cellulose + clay plaster for round pole timber frame
I am building a round pole timber frame using a professional designer in Southern Wisconsin (whole trees) for a small house. For the wall assembly I originally planned straw bale + plaster but after discussions and consideration I wanted more height with no second story overhangs, and no moisture problems down the road. So I’ve decided to use 10-12″ dense pack cellulose as an in-fill between timbers.
I plan to use horizontal girts on both sides of timbers, and use dense-pack cellulose with netting on both sides of girts to hold it in. On interior I’d like to use wood lath + clay plaster because it will serve as an air barrier and we have clay so it’s embodied energy is low. And it’s cheap and beautiful. I know it’s not common. On the outside of exterior girts I want to fir out a bit and put vertical wood siding panels, with some weather resistant paint or finish on back and end grain.
What I want to know is do I absolutely have to sheath this? It may be in the code, and I know reused foam is cheap and can double as a WRB, but I sense that sheathing isn’t structurally necessary in this design. Secondly, even if condensation builds on inside of the siding it’s firred out and can drain. Regarding fire risk, cellulose is resistant. I think a WRB would probably be a good idea with cellulose behind wood siding, but I can’t think of a good way to attach house wrap besides on the underside of the wood siding itself which is logistically impossible I think, so back to foam. I’m really trying to avoid more materials than absolutely necessary from a simplistic perspective, and especially foam. But it’s my first and maybe only build so I’m probably naive. I suppose I could use lath + plaster on exterior of cellulose and put firring strips in the plaster for the wood siding, but that seems pretty labor intensive. I don’t want a plaster exterior, just don’t want to deal with the maintenance if I can use wood siding.
Any suggestions welcome!
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