Some years ago we were asked to help design a wild-life observation centre at North Cave in East Yorkshire. We came up with a reciprocal roof structure which provided an unobstructed viewing from inside the shelter. The timber frame allows consecutive roof members to rest and dove-tail into adjoining members around a central point.
Walls were then formed with plastered straw-bales. We tried to use as little steel as possible so that all joints were hand-made.