Oriented Strand Board is less expensive than plywood but you do have to add a weatherproof finish either way. I'm finishing the build of a small loft and if you want you can see the step by step fotos of my setup under the media tab on my profile page. I will upload a pic of the perches I installed soon.Thanks for that link! Being in the smallest state I don't seem to have lots of local options but I'm not getting birds anytime soon anyway, I'm going to get the actual construction all done first. Admittedly I wanted to keep the loft the size it was in order to buy the smallest amount of 4x8 plywood sheets but whatever is better for the birds. Also typo on my part lol, I meant less than 10 birds.
I hear what you're saying about the aviary being on the larger side, I'll probably trim it down a lot. If the floor of the aviary was also covered in hardware cloth would it still not be safe? I mainly wanted it to touch the ground so I could put some sand or something down for easy cleanup and also so that I could step inside it for whatever reason.
Your drawing program is pretty cool!


. Let me explain. Frame out the 5 x 6 floor area and make a thin floor, maybe 2 inches thick. It is predator dig proof and will not cost all that much. I bag of Portland cement and 5 cubic feet of sand will do the trick. You do not need anything stronger/thicker since your loft is nothing in weight to consider heavy. If you have never done cement, no problem. Watch Youtube, and the job you do will be just fine. No one will see it except your pigeons and you. 

