Ferrocement (q.v. my www.fantasticferrocement.com) is the physical strength of all havens;but this still allows such things as interior wood trim, desks, shelves etc; and interior walls of clay plaster if desired. I am calling the particular method I am now developing (28/4/15) for the Dream Havens ‘Hybrid Wattle and Daub’.
The hybrid wattle and daub method of haven construction (invented by the Wizard of Eutopia) uses cast ‘nautical’ concrete arches and woven wire ‘wattles’ in two layers, plastered outside with a waterproof nautical plaster ‘daub’ as used in ferrocement keelers, and inside either with white plaster for a whitewash panel and beam effect or using your own local clay ‘daub’ for a more rustic (and local) feel.
Between the layers is your choice of insulation – wool, fibreglass or polyester.
The arched beams are partly exposed, and inside can be capped with wood, stained in a stone finish, or painted.
All in all, a nice solid English farm cottage or Hobbithole construction (or Elven if you wish, with carved features and fittings), with permanent, non-toxic materials to last you well into the Fifth Age.