Enclose ?/ heating ?

I have build some enclosures for my leopard geckos. 1x3 frame with 1/4" birch plywood and 1/8" tile-board on top of the plywood for the floor. Three stackable boxes 2'x5'x14" split down the middle with a divider for a total of 6 separte living spaces.

I am still trying to decide upon whether to build sliding glass doors or to frame the glass and hinge it. The cheaper method would be the latter, but it reduces the visability and looks bulky. Any ideas for cheap tracking is appreciated. So far the materials are under $100, which is extremely cheap IMO for an enclosure this large (not including heating). I have glass from an old screen door that I will cut for two of the enclosures. So all I have left to buy is glass for the 3rd and the tracking/frame and hinges.

I am unsure if I should polyurethane (water based) the interior walls and ceiling or leave them natural. Since it is for leos the humidity will be low, but urethane will help reduce any chance of fungus and make it a lot easier to clean. But I am nervous of out gassing harming my babies.

Finally, my heating questions. I have order 11" flex-watt heat tape and a Zoo-med 500R thermostat (only reason I did not go with a proportional was $). I was planning on mounting the flexwatt under the plywood where there is a 1.5" space between each level. I was going to mount 2' under the divider so there would be half in each enclosure (5.5" on each side the whole 2' width). Will the flexwatt be able to heat through the thickness of my floor. I would rather not put it in the enclosure. So, if underneath is not feasible, could it be sandwiched between the plywood and tile-board. I've heard it can over heat when sandwiched. Does anyone have experience with this? Will the tile-board conduct enough heat to eliminate over heating?

Thanks for reading through such a long post. And thanks in advance for any input.

In regard to the glass door track - go to Rockler Hardware (they have an online store) - they have both plastic and metal track hardware for pretty cheap. Some people get tempered glass cut for their cage doors because it's less likely to break and if it does break, doesn't have as many dangerous splinters as normal float (window) glass, but that's just an option.

You SHOULD probably waterproof/polyurethane the interior of the cage to make it last longer, and so it won't hold bacteria. Even though you plan to house low-humidity animals, the wood will soak up feces and other material unless it has been waterproofed, and would be difficult to clean and sanitize. The key to not "gassing" your reptiles is to wait several weeks after you apply the waterproofing to let any possible fumes "offgas" before using your cage with your animals.

For the heat - others could probably answer better because I haven't heated custom enclosures with flexwatt before, but risks of overheating when sandwiching flexwatt could probably be worked around by using a thermstat (that way, if the flexwatt starts overheating, the thermostat would automatically turn it off) - which can be purchased for as little as $25.

Hope this helped.