It's me again..
Yes I have converted shed, though not quite as big as yours..6x4. There is no problems having a shed rather than purposely built chicken coop..actually it can be much better construction with few little extras.
To start with...my shed is raised on breeze blocks ...rats like to burrow undernearth and having it raised will help keeping unwanted recidents away...they can still get in if they really want but having 'airy' space doesn't attract them as lodgers.
I cut hole through front wall for a coop door...and shed door has long hook with eye too for extra opening during warm summer months. I have put indoor ventilation 'thingy' on wall near top as well..it is all about ventilation..ventilation..they can cope with cold but damp is what makes them unwell.
Halfway up on one end I have put few lengths of wood (wall to wall) to form open shelf that house bag of chopped straw for their bedding indoors and bag of mix grit. Underneath all that, about foot off from ground is their perch...3" thick tree branch (again, attached from wall to wall)..other end of shed they have their nest boxes that I built and they've been permanently attached on the wall..inside, as I prefer go in collect the eggs. There is another solid base shelf too for all those 'essential bits and bobs' and their food bin is stored there too. Near door I have screwed small metal tin on the wall...few inches off from floor and that I keep topped up with grit all year round as well as their supply of it outside as well.
The floor is kept just bare wood but all other inside surfaces are painted..walls with various pale paints (what is left over from after decorating in house)..that has two purposes...to lighten up otherwise dark interior and seal all the little cracks in wood where mites and other creepy crawliers may hide and when you do your annual pest control clean up..you can see if anything comes out from wood work. I've used 'lashings' of the pain..no expenses saved
..to make sure there is as few gaps as possible. Undernearth the roof is just wood treated.
I recovered the new roof with new material as soon as the shed was installed..got some of those corrugated bitumen sheet and allowed very generous over hand so no rain water has access anywhere near walls and shed is kept dry..VERY IMPORTANT!..you do not want any dampness inside!!!
My she has two windows..one has glass on permanently but other is 'open' and I have attached just piece of chicken wire over..it is left fully open during summer months and for winter I temporarily attach partial cover...clear polycarbonate sheet piece that is short of a inch of the opening..that leaves tiny ventilation gap when I insert the sheet into frame work..and as the roof has that generous over lap..the rain doesn't get through the gap neither.
It is important that if you have generous size shed that you also house more than just few birds in it...their own body heat will keep the indoor temperature acceptable for them during winter..too much 'empty space' and they get bit chilly.
I don't want/need many chickens so 4 to 6 birds is plenty...but to keep them cosy in their shed I have that huge bag, or two of straw stored just above them. When they were younger and lighter, they used to 'fly' on top of the bags and squeeze to roost there..
