right now Im working on my 3erd cage these one is 60X24X18 inches and im using 1/4" reinforced with 2x2 on the floor so that I can tape the flexwatt directly to the bottom, on top of the 1/4 mdf floor Im placing vinyl stick on tile to help with spills and urine, on one of my cages I had a problem with the floor of just melamine, mind you I was new at these and was using aspen for bedding so I wouldent notice urine and would not clean the cage for weeks at a time so the melamine did bubble up a little, now since a burm is going in the one Im making and they can get everything really wet Ill use the vinil.