Ok, I have several questions on this project that i am envisioning.
I have an attic full of random lengths of scruffy/used but unfinished 2 1/4" wide oak flooring pieces, tongue and groove.
I have a 66 square foot bathroom (our main bathroom) that needs a new floor. (It's currently crappy painted particle board on top of the subfloor, which is old school diagonal 2"x6" boards.)
I have this plan of sanding down the oak flooring out in the shop, cutting down the pieces into 9" lengths and creating a homemade parquet floor, with a simple 4 strip pattern repeating itself at 90º to the last group of four.

So begin the questions:
1. Do i need a solid subfloor like plywood or can i fasten to the existing boards?
2. do i need a vapor barrier/membrane or am i better off letting the subfloor and parquet breathe out the bottom of the house? (We are on the first floor of a piling-built house: i can crawl under the house and look up and see the subfloor.)
3. Should i utilize the tongue and groove that exist and at least have three tongues going into three grooves out of every block of 4 strips of wood? I can't think of a way (other than getting and learning a router) to create tongue and groove joints at the points where one long side abuts 4 ends... Is it a crucial connection?
4. I read about how most modern parquet floors are glued down. Are they ever nailed? Why/why not? i am tempted to nail rather than glue so that i don't run into bathroom moisture/glue failure issues down the road, but will nailing create other, larger issues?
5. Water-based mastic type glue? Recommendations for bathroom environment?
6. Sealers. I have a couple gallons of Varathane water-based floor finish. How does that do on a floor that gets wet sometimes? (but not crazy wet - no kids, pets, etc) Will it create a seal so that moisture doesn't get between the cracks of the parquet pieces and compromise the glue or the subfloor? If it isn't appropriate, what is? Gym floor type product?
7. Can a floor like this support a clawfoot tub? (the existing floor does, so.....)
8. And finally, is this just too crazy for a moisture place like a bathroom? Am i nuts for taking it on? Should i settle for tile?

I know this is a lot of information requests, but thanks for giving any info/opinions you might have!
kbt