The first question you should be asking "do I have enough room for my chickens". Firstly chickens are a social animal and they need to be with other chickens. Each full size chicken needs at least 2 square feet (0.1858 square meters) of floor space in a shelter/coop. They also need another 3 square feet (0.2787 square meters) of outside floor space (i.e. in a run), that's if the chickens are not running loose.
For an example, a shelter for 4 hens would need a floor space of about 2ft by 4ft, and for a outside run they would also need an additional area of about 2ft by 10ft.
Height wise their coop doesn't have to be more than 3ft high, although you many want to it to be tall enough so you can walk inside the coop/run.