New sunroom - need flooring advice, please!

[Warpy]

3. I'd go for the old standards, tile or slate

because they don't tend to suffer much from temperature changes.

Eventually, though, any floor you put down will fail if the only thing you have on top of soil is tar paper and plywood. What you need to do, really, is have a concrete floor poured over the tarpaper. Then you can put the tile on top of the concrete once it cures and it will be stable. The tar paper will keep it relatively waterproof.

If I were doing a temporary floor over the kludge plywood/tarpaper floor, I'd do cheap laminate since that floor is going to fail sooner rather than later.