Hi Michael, as you can see I was finally able to register, using another computer this time.
This was quite something you have described. I'm sure you expected something that would just fall in place and I would have had too. I was in a lecture about three years ago where someone was explaining how to build an outside aviary. I could not afford to buy something like yours and in reality, it would not satisfy my security needs. So he was telling us how it should be done and why. The only material I would use is stainless steel; it is the strongest and the hardest to break and it will not corrode. When coating gets scratched you will see the steel rust in no time, specially outside. They sell stainless steel mesh in the US but the problem is I live in Canada and you have to order quite a large roll of it, unless I find someone to share with me and it's not obvious.
It is also imperative to build a double wall, the inside mesh in stainless and the outside one galvanized. Why? So no wild beast can try to eat my parrots or even touch them and make them sick. The walls should be spaced something like four inches is I recall well. Second, you need a roof, so they get shade and no wild birds can poop on them and transmit aviary flu.
I would also like to have a concrete base to make it easier to clean and cleaner.
So, after figuring out the cost of the materials, I decided to forget about it until I win a lottery
It would need to be strong anough to withstand the humongous amount of snow and ice we get here in the winter also without collapsing or getting damaged, so the outside mesh would have to be quite strong.
One more safety issue I almost forgot to mention. A double door is also a must. When you go in the birds can fly out in a flash very easy. Half a second of inattention and it can happen. Sometimes when they are out in the house I tend to forget and will go answer the door.
One more thing. Getting the birds stolen is always a possibility. No cage can ever stop someone who really want to get in there. You can use gig wire cutters and get access in only a few seconds, no matter how strong the mesh or the steel is. Having something to support that would mean super heavy duty stainless and probably cost 5,000$.
With all the trouble you had putting it up, I hope they will enjoy it and it will be a safe place for them.
A cam is a good idea also.
You are in the big city. I live in the country with racoons, eagles and foxes and more so I would not take any chance.
Have a nice day.