Height of coop depends on how tall you are, and how much you value your back. I'm short. So, if I was designing a small coop for my purposes, with the criteria that it be a walk in, and that it must accommodate deep litter, I think this is what I'd do. 4 x 8 foot print. Shed roof, with good overhang on all 4 sides (6 - 12" overhang) I don't know what the pitch would need to be, cause I'm not good with figuring pitch. But, it should be adequate to shed snow load, if you are in snow country. If not, it could be a shallower pitch. High wall would need to be in the front, South facing. Short wall to the back, North facing. Short wall should be at least 6' tall. (8' x 6') Front wall, depending on pitch, possibly 7' (8' x 7') . (I think that's a 1:4 pitch) That gives a nice looking angle to work with. People door could go on front wall, or on either East or West wall, depending on your typical prevailing wind patterns. There would be plenty of room, height wise for roosts along either the east or west wall, while still allowing space for ventilation well above the roosts. Placing roosts on short wall allows the birds plenty of room to fly down off the perches. You could put in full length soffit vents on South and North walls, And perhaps a louvered vent at floor level on E or W wall, opposite the pop door which would be 1' above floor level. You might want to put a 1' high window along full length of south wall under the eave. Then, put in at least one more window on a wall of your choosing.