I have built several outdoor as well as indoor aviaries, I actually built one for my breeder budgies to retire to about a year and a half ago when I decided to stop breeding. My house is a split-level and the walk-out level that is connected to the garage includes a half-bath/laundry room, a foyer that has a very large, antique wood stove on a brick pedestal and a ceramic tile floor, and then a very large room with a ceramic tile floor that I was using for a workout room prior to building the aviary. The room has one window that is actually ground level with the front yard, a couch, a flat screen TV, and then I decided to build a free-standing aviary that can be moved if need be. I was going to build it right onto the wall but thought better of it since I've changed what I use my ground level or "basement" for.
I started out building custom enclosures for reptiles a long time ago and did very well at it, so then started designing and building aviaries...There are soooo many options and soooo many ways of building them, the options are endless!
I have a bunch of photos of every one I have ever built on a flash drive and a CD-RW in my office, I'll load them up in a minute and post some.
Do you want to make a free-standing aviary that will sit on your balcony, or do you want to turn your balcony itself into a big aviary? I've never done a full balcony redo as far as making the entire balcony into one big, dedicated aviary, but I've seen them before and it's a very cool idea, as long as you're willing to give up your entire balcony. I've also seen a lot of free-standing aviaries that sit on balconies, usually they are taller than they are wide, and they are typically either built into one of the corners of the balcony and use the two existing walls of the building as walls to the aviary, or they are a completely free unit that is simply sitting on the balcony.
"Dance like nobody's watching..."