Hi Everyone!
I don't get an opportunity to post (or read) on this board anymore, but I Have been a member for... oh dear... at least 7-8 years. (I feel old) A couple of years ago I built a cage for my then very-juvenile Uromastyx Aegyptius, though he lived in a 40 gallon breeder until he got a little bigger.
Now that it is 2.5 years later, I have been contemplating changes I would make to my initial design, if I were to build a new cage.
The initial cage (picture below) is 4x2x2.5ft, with the lights sitting on a false ceiling 6-8inches (I can't remember) from the true ceiling.
Things I would do differently:
1) Over time, the extreme heat inside of the tank has warped some of the thinner trim pieces that I used, and has "loosened" some of the main joints. Neither of these things has effected the structural functionality or safety of the cage, but what it has allowed is sand to slowly spill through the small cracks in some of the joints. Not a huge issue, but a real pain to clean! Additionally, I can see light through some of the gaps, which is *purely aesthetic* (we are talking @ 1mm gaps) but being a perfectionist drives me nuts.
If I did it again I would do a few things to minimize these things. one, I would reinforce the joints with more than nails and wood glue. I would consider using metal "corners", or L brackets, on the outside of the tank since they would not move with the heat variations like a nail and wood seam will. Screwing the main box together instead of nailing it might help as well, however I don't think that I could have done that with the 1/2in plywood without massive splitting.
I also would have sealed the internal seams with silicone, or some other non-toxic, animal-safe, heat-safe (most plastics will emit unsafe fumes if heated to 120 degrees), flexible material. Then even if the seams did expand and shrink a little bit the sand would stay where it should be, inside the cage! lol
2) The living space that I built is MUCH taller than necessary, and that equates to it being somewhat difficult to reach proper basking spot temps, and it costing a lot more than it would otherwise. This was less of an issue while I had a "real job", but now that I am in grad school the electric bill is painful. If I were to do it again I would make the distance from false ceiling to main floor 6-12 inches shorter. I would not make it shorter than 18 inches though. One, because I like to be able to see the lizard. Selfish but true. Two, he seems to somewhat enjoy, or at least amuse himself, by climbing on some of the branches. (Yes there are a variety of reasons this could be; including an innate concept that "up" is hotter, or an actual temperature gradient, due to my limited observation I would agree these are possible, as well as it just amusing him, as much as a lizard can be amused) If I were to do it again, I would add a "false bottom" to the cage as well I think. (see "ideas I am mulling" )
3) I would add insulation to the area that allows access to the false ceiling, and all of the lights. I believe that a lot of the heat is actually rising out of the upper back of the tank, making it even harder and more expensive to maintain proper temps. (I could do this now, just haven't)
4) I would use wood slides for the glass instead of plastic ones. I was warned about this, but had already purchased the plastic slides. I will have to replace those long before the rest of the cage *has* to be replaced.
Things I would absolutely do again
1) make my own cage, it functions better, and is much nicer to have in my living room than almost any purchased ones I could find, and definitely than any purchased ones I could AFFORD, lol.
2) Use the two glass pane side-pass construction for the front of the tank. I think that Mosca is much more comfortable with me coming from the front of the tank, than he ever was from the top (duh, I would be too, lol). It is next to impossible for him to open, and I can add a lock if I need to as he gets stronger. Observers get an unobstructed view of the front of the cage. (since the other 3 sides are wood there are "mosca only" places for him to hide as well!) Additionally the door is easy to open with one hand when I am feeding, and allows the "doors" to be large, giving me easy access to the entire tank while cleaning. (an important an easy to forget topic, lol)
3) Use a false ceiling design. For my piece of mind I know that Mosca can NOT get to the lights, or any wiring, and it makes light bulb changes relatively simple, without even requiring me to disturb Mosca's living space. Though I am sure the "sound from above" is disturbing to him. (he usually sits on a rock an watches me from below)
4) I would still use large castors on the bottom of the tank. What I would NOT due is lock them, forget they were locked, and then push the tank around. This results in castors breaking off the tank. It is *very* difficult to replace castors on the bottom of a very heavy tank full of sand!
Concepts I am mulling over
1) Adding a "false bottom" with an access door on the front of the cage, and putting a network of supported, clear, tubing in it with Mosca access from multiple location through holes in the "floor". My idea is that this might allow him the idea of tunnels (and cooler, higher humidity hides), while still allowing me the ability to find him if I haven't seen him for a few days. The concept being that it would be extremely dark in the sub-floor area, so he would not care the tubes were clear, but if I couldn't find him I could open the access door and see him once the area was illuminated.
2) Uromastyx "hamster" trails - connecting his main tank to other smaller tanks, and exercise areas through a network of tunnels in my apartment. There are MANY concerns and design considerations that would have to be addressed here, but once again the idea would be for him to have access to a lot more space than I can give him in a traditional cage environment. (and a lot more access to it than relying on me to let him out and watch him the entire time)
3) Giant underground Rete's stack - so, back to the concept of a "false floor", only instead of a network of tubing, building a Rete's stack that would take up the entire space, with holes for him to access each layer through.
Conclusion 
All of these considerations are of course because I am trying to find a compromise between his "natural" environment (which he has never known); my worrisome (and good parent) behaviour that requires me to be able to find him if he hasn't been seen for a few says (unusual for him); and my desire to have him in my living room. Ideal would probably be some sort of large, deep-dirt layered environment safe from predators, with good food and good temps. I struggle with the discrepency, but have come to terms that by making him a "pet" I have already taken him out of his natural environment. So, strive to make his existence as enjoyable and healthy for him as possible.
Thoughts and conversations are welcome! Please be considerate and kind of your fellow Uro lovers on this board! I hope that at least one person gets some benefit from this monstrously long post. LOL
Elizabeth
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1.0 Mali Uro Archimedes (May he rest in peace)
0.0.1 Egyptian Uro Zuberi Mosca Khu (Mosca)
0.1 Sulcata Minnie
1.1 Iguanas Flik and Loki
Madison, Wisconsin
a real nice post here, helps people who may be planning a cage get some good ideas. 
