If you check on amazon.com or possibly on the book link at the top of the page there is a wonderful book called Cages and Aviaries that has plans for all shapes and sizes of aviaries.

We have built a few indoor and outdoor aviaries and one thing you do need to be careful of is purchasing stainless steel "mesh". Most of the mesh or hardware cloth you can purchase at local hardware or building supply stores is zinc coated. Some people say it is safe if scrubbed with a wire brush and vinegar others say it still has too much zinc even after doing this. I like to be safe instead of sorry and try to avoid it for bird cages. Let me know if you can't find the book or need any other help!