Pretty much all the common chicken predators can climb, except for canids (foxes and coyotes). So don't count on critters not to climb. And pretty much all of them dig, too, including canids, so your apron should ideally be high priority - hardware cloth as opposed to welded wire with larger openings. You can get away with welded wire higher up on the fence, if your coop is completely predator proof and your chickens sleep locked in it at night. That way they'll be safe at least during the night. Small predators can still get in during the day, but it's less common than at night. I've had to make that compromise myself, because HC is so expensive, and I'd need a lot of it to wrap my large run. So on the top half of my fencing, as well as overhead, I have welded wire as well (2"x2" on the fence, and 2"x4" overhead, to allow snow to fall through). I can try to eventually cover the walls with HC as well, little by little so the expense isn't all at once, but I need to avoid snow load on top, so the top will have to stay 2"x4" and still exposed to smaller critters... But at least my coop is bomb proof.
How about this one:
