Go to the Cage & Habitat Design section: forums.kingsnake.com/forum.php?catid=4
There have been a lot of good discussions recently on materials. You should get plenty of ideas from within the first 2, maybe 3 pages. Well worth the time it takes to read.
Melamine is pretty much the all-time favorite due to its relatively low cost compared to other options. However, melamine, alone, won't quite do it.
You'll definitely be needing something bigger, soon, if not already.
As for heating your 30gal., a UTH would work along with an incandescent, flood or ceramic heat emitter.
If the cage sits off the floor and room temps average in the 70's you may not need a UTH. Get a dome reflector lamp with a ceramic base, a dimmer switch (Some domes made for reptiles come with one already installed, or, you could get one at a hardware or pet store and install a dimmer switch.) and get incandescent, flood (75 watts) or ceramic heat emitter (100 watts) with plenty of wattage and you can adjust the output with the dimmer.
Make sure that the dome is deep enough or the bulb is short enough so that the bulb doesn't rest directly on the screen.
Set the dome on top of the screen lid, to one side or the other, so it creates a gradient temperature within the cage. To help retain humidity you can place the water bowl near the heat source. You should also cover as much of the open space of the screen top as you can to hold more humidity in. Use either cardboard, preferrably with a waxed side facing down, or anything else. Just make sure it doesn't come into contact with the dome or bulb.
Have a good one!
HH
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