This oak playhouse, by James O’Keefe, was built with roundwood timbers and waney edged planks and has wild flowers in its green roof. See the step by step construction at www.naturalhomes.org/the-wee-dinky-house.htm
Concept: putting a vine, eg passion fruit, choko, etc over the garden shed to cool it in summer and make use of the vertical space for food production, plus it looks more appealing. Could even grow different vines at same time to add greater visual and food interest. Plus, Great book, apparently ;-). All you need to know about how to build your own little green roof on a shed or outbuilding.