The planning has begun...
After great consideration, we have opted for an octagonal set of upright posts, linked by their tops with a ring beam. This ring beam will carry the weight of the rafters which will form a conical roof. The roofing material has yet to be decided. Wheat straw thatch is currently £800 a tonne so not viable. Turf stripped from the site is a sustainable option but has structural implications due to its weight when saturated. We have opted to leave the roofing decision for the time being and proceed with the structure.
Below are two images of the plan and side views proposed. Final dimensions will be a function of the available timber: