Our shed was built to keep the avian folk warm in our very cold winters (-20F for weeks at a time).
8ft x 8 ft and something like 10 ft high. It has a front door that has two locks (for those bears and foxes which have opposable thumbs).
It has like 3 metric tons of rock poured into its foundation (do not ask me, ask the husband) which is composed of pier footings and a simple joist system. We put down a very close wire fabric on the joists before we put the subflooring down. This is so we can keep the fox and fisher cats at bay (have had exceptional problems with predators). One layer of pressure treated plywood and then a layer of non-treated (we didnt want the chickens to be exposed to the chemicals).
The walls have two skins with insulation between. The roof is made of clear material ad there is optional venting up there that has been closed off with more wire mesh (fisher cats climb anything).
I will be building the next boxes closer to the time that the girls start to lay.
There is a second shed which is dedicated to wood. We have a woodstove that we heat our house with so we need to store our wood in out of the snow.
This is all evolving. We are building a connecting deck between the chicken house and the wood shed which now has a back part that is decked (for the husband to do outside things and to store stuff.
There is an area on the front of the wood shed for cutting wood.