Buy your lumber in 10 foot, 12 foot, and 14 foot lengths.
Before doing so make sure that every board is square and even on both ends and that if not be sure that it is a fraction of an inch longer so that both ends can be squared up at an even 120 inches, 144 inches, and 168 inches.
Buying from a real lumber yard where they quote prices in board feet and not a big box retailer were a 16 foot board lets say costs 3 times, not twice more than an eight foot board cost will save you mega bucks.
By using the 5 foot, 6 foot and 7 foot coop and run plan you will only need to cut each 10, 12 & 14 foot board into two equal parts.
No extra cutting and no waste except for the saw dust that comes out of each saw cut or kerf.
Buy one 4X6 landscape timber and use the narrow (4 inch) curved section for the roost. You can even rip the landscape timber and get 2 eight foot roost or 4 four foot roosts.
There is nothing in the regs that should keep you from having an overhang so you should think of using boards longer than the walls so you have good drainage and less blow water.
If you wish to hen incubate chicks DON'T, I repeat, DO NOT build fixed nests into the pen or coop design. Instead spread a few nest boxes on the floor of the coop or run and that way you can pickup the broody hen, eggs, nest box and all at in the dead of night, and move the whole shebang into a small garage or basement pen for the 21 days or 3 weeks it takes a hen to become a mother and there is very little chance that she'll abandon the nest because of a gross disturbance.
Good luck and don't hit the wrong nail.