All aircooled Volkswagens use a pan instead of a frame. Because of this, the heater channel (the bottom piece of body metal attached to the body) and the pan, are structural. Heater channels are hollow to allow heat from the engine to enter the cabin to warm the car. The problem is, this can cause moisture to enter a difficult to dry area, which then rusts and rots out and then transfers rust to the floor pan.

I'm a hobbiest so dealing with this issue hasn't been the worst thing in the world but it has hurt my ability to drive the car. I am so glad the floor's been replaced. If you're used to cars with frames, make sure to check the pan and heater core for damage and flex. Ask if they've been replaced, and make sure you're either good with a welder, or know somebody who is if you buy one. Otherwise, they're very easy cars to work on. This is their biggest design flaw.