[avocollector]

Definitely get it up as far as you can off the ground. The difference I noticed between my sheds is with a foot or so of space underneath the moisture is significantly lower so tools don't rust etc. Get it up then place a layer of plastic sheet under the flooring - the walls can be treated as G6Tanuki suggests or 2x 2 battens bolted screwed to the frame, moisture barrier and glass fibre insulation followed by 7mm ply on the inside (heavier is even better for shelves etc.). What I'd like to do with mine (only 10sq m) one day is devise a low level heater - perhaps run off photocells on the roof and couple of car batteries that kicks in say below 8 Celsius to reduce condensation. Definitely insulate the roof - in the Summer you will be grateful for that. Cheers.