3m x 2m approx.
Thinking it may be easier to build a frame on the inside to take the
roof load, independent of the walls. Similar to this, but mine just
has brick walls:
http://www.woodheat.org/firewood/woodshed.htm
Thanks,
Tim.
wuold help if you gave some idea as to size. Joist hangers, or joists
can be cemented into a wall. For non habitable you could use garden
wood or large firewood for the roof structure.
NT