hardboard which way up?

[ladylola]

Just my tuppence worth.
I've seen and been asked to fit it both ways but predominately it's been rough side up and commonly fitted wet so as to shrink and go taught rather than being able to expand once down and create "waves".

 

[Karis]

I don’t know any experienced or pro tiler that would advocate tiling over hardboard. Old post resurrected but if you’re seriously considering it, I would strongly advise you not to, it's a failure just waiting to happen & you'd be asking for trouble.

Johny2b; If you need advice about how to prep your floor for tiling, visit/read/post the Tiling Forum.