When I built, I was going to have a feed room but opted for a built in lidded bin to set the feed sacks into. I don't see people planning a secure critter proof storage beside a occational galvinized trashcan.
I would love to do this but our coop is too small. I am thinking of buying or building a wooden chest type thing (I see them at the 4H fair a lot) to keep feed in but would still need it in a trash can or something inside there because it wouldn't be waterproof.
Takes up valuable room that's needed for the birds. Especially in the winter when their sometimes locked up for days at a time. I have two metal trash cans in front of my coop.So far they work & the feed has stayed dry & no predators have gotten in. I use a buggy chord to secure the lid.
All of my feed and hay are stored in. 20x20 building with a/c in it. Each feed is stored flat in it's bag on shelves until opened and dumped into a trashcan with lid. All cans are labeled so there is no confusion from chick starter, game bird, layer crumble ect. Makes for easy storage and easy inventory.
I ordered another metal building last night. 14x10. We are going to put a couple small (pygmy) goat stalls, a stachion for milking and feed storage, plus hopefully room for a few bales of hay. We have another location to store more hay.