If you are getting a hatchling, you definitely want to start it off in a smaller cage; something like a 3' x 18" cage is plenty big. This smaller size will help your burm acclimate much more quickly, it will allow you to provide optimal temps/humidity levels and will provide a better feeling of security. Or, get a 4' x 2' cage which will allow you to keep up to a 8' burm, while still being okay for a baby burm, and once it reaches that size, you can move it to its permanent set up.
You will hear MANY folks say that a cage that is 8' x 3' is big enough for any size burm....NO WAY! Although many of my burms reside in 8' x 3' cages quite comfortably (neodeshas), our 18' , 275 lb burm would be squeezed in a cage that size. Instead, she resides in a cage custom made by Habitat Systems complete with natural rockwork that is 12' x 4' x 3' (width x depth x height) and this gives her enough room to move, thermoregulate and feel secure. This snake comes out once or twice every week or so for exercise. You don't need to incorporate a pool in your burm's cage. I have kept burms well into their 20's/30's and none of them ever had anything bigger than a really big water bowl (we get plastic troughs from an agricultural supply company). We heat our boa/python/venomous cages with pro product radiant heat panels (perhaps the finest heating device available) and our burm's cage is lighted with two 48" 5.0 zoo med full spectrum fluorescents to give it a nice light for public display. If you prefer to have a potentially smaller sized burm, go with a male as they typically top out at the 12-14' mark whereas females will easily exceed 15' (and much more weight). In terms of glass, if you get 1/4" tempered glass (or thicker) you will have absolutely NO problems with possible breaks. Have fun with your new burm and ask as many questions as you feel necessary.
Rob Carmichael, Director/Curator
The Wildlife Discovery Center at Elawa Farm
City of Lake Forest Parks & Recreation