Why aren't unfinished red oak boards at least treated or sealed on the bottom side to deter termites and rot? If they are, I want to know which water-based product to use. I'm installing oak in the kitchen.

Second, which environmentally friendly water-based urethane product will provide a durable clear satin finish for a kitchen? I'm a pretty resourceful non-contractor, so a two part product might work, but I figure that I need one which can be buff sanded and recoated every other year or so.

So, it seems like it would be nice to have a two part finishing process. Sealing and finishing.

If termites get to your oak wood floors, think of the damage they could be doing to your subfloor and joists. All the wood, including the framing, needs to be protected from excessive moisture, which attracts termites. Proper grading, drainage, air flow, ventilation and on grade vapor retarders are the way to prevent moisture damage.