My wife and I will start building a 14-15 ft diameter earth bag round wall cabin this June. it will be built on a 4 ft deep rubble trench insulated with earth bags brought up to grade. We will be using a mix for the bags being 25% clay 75% sand (only exception being the first course on rubble trench will have gravel in them) We are building in the Upper Peninsula where we get lots of rain and snow. We have a working span from June till mid-late October before the winter begins, so having the plans as complete as possible is crucial, also this will be our first earthen building so we are trying to keep it as simple as we can.
Question we have, is a bond beam necessary for such a small structure? Or would velro plates under the rafters suffice?
One last question, and this is really where were stuck at the moment, is roof ideas? Right now were contemplating a gable roof. Because of how small our structure has to be (because of building codes) we would link to incorporate a sleeping loft.
Right now were thinking from the inside out having our layers go like this, boards that we cut, one inch think white bead board, rafters with straw stuffed between, and another one inch thick white bead board on the other side of the rafter, we would put a layer of heavy gauge plastic over that, with sheet metal being the last layer?
We will do a post and beam structure on the outside of the house, so the roof would mostly be supported on that.
Any comments or ideas would be very appreciated.