First you put down the cement backer board. Home Depot, Lowes and most every tile store has it. If height is an issue, there used to be quarter inch available, but I haven't seen it in years. Hardiboard is half the thickness of standard cement board, but will cost twice as much.
What type of subfloor do you have? In California on the Pier and Beam homes I worked on, they had tonge and groove 2x6's with 5/8's particale board as the sub floor. I'd take off the particle board as it was usualy the probelem anyway, and attach the cement board to the 2x6's and be at pretty much the same height after installing the tile as the original floor.
When my parents first started putting tile down in our rent homes, they just used a mastic to attach the tile to the wood foors. I was miserable stuff, but we never had a tile come off. I don't know of anybody who still does this, or if you can still get that type of mastic, but the tile is still down in those houses 30 years later.
If your floor has any flex to it, tile wont stay.
Eddie
