Building a cobwood roundhouse over a six week course in six weeks, Spring2008 at Denmark Farm, near Lampeter, West Wales.
A couple of answers on construction - the ends of the posts are charred in a fire to about 20 cm above ground level. These are chestnut posts here so they should last 30 years or more. Sometimes I also paint molten bitumen onto the post feet as well. The yellow pipe is a drainage pipe which goes under the polyfelt and is taped to the plastic/rubber roof membrane. It collects excess rainwater and channels it to one point on the eaves where it could be collected for watering etc.