Size is determined by the breed and number of birds you intend to keep. For layers the floor space should be 2sqft per bird. Broilers 1 sqft per bird. Should be built on an east west orientation, solid wall 3ft high, remaining part of the wall should be meshed with chicken wire. Highest point from the floor not more than 8ft. The shape to be rectangular always. Concrete floor with dry little recommended in deep litter system.