Aart has good advice. I live in the NW. don't be too attached to free ranging, IMHO, it's harder on the birds than you might think. the typical fence will do very little to deter predators. for a large area, electric is necessary but a pain to maintain. Along the OR coast you will need protection from heavy wind and rain more than cold. I've been to a lot of wet places on this planet and I've never seen heavier rain than along the OR coast :~). I'd make the run completely covered with some kind of provision for a wind break and or extra deep eve to keep it dry in the driving rain. chickens are happiest if they never get wet and there are not health benefits to it, they like dry. I'd make the run large enough that you feel good about it if they end up staying inside it all the time. the only thing I've found adequate to keep the critters out is Hardware cloth, wall to wall, ceiling and floor (under about 8 inches of deep litter), galvanized U-nails to posts, overlapped at the seams. home depot sells concrete blocks with an elevated post base, keeps the wood away from the wet. I used those and laid down the hardware cloth first, mended the cloth that goes under ground with thick black zip ties. it's really best not to "wait and see" if you have a predator problem, they are inevitable at some point and much harder to deal with after they succeed in getting a bird or two or three.
