Preparing wood subfloor for ceramic tile
If you want the same heights, install tile in the other room too. The kitchen will be from 5/8-3/4" higher if you go with a "thin set" method. The alternative would be a good ole-fashioned "mud-job" which would be about 1 1/2" higher.
You need to start with a flat subfloor. So repair or replace any warped or cupped boards. Re-screw every board to every joist, 2 screw per if possible. If the floor is not flat enough for the above to correct it, you may need to do more than just re-screw?
Now you have to install a proper plywood underlayment. Make it as thick as possible, but minimum 1/2", prefer 5/8" or thicker. Then comes 1/4" tile backer set in to thin set mortar and fastened etc. or you can go "Premium" with Ditra which adds only 1/8". Then the easy part, the tiles.
Tile 4 You LLC Troy, MI
KERDI Shower Specialist ... DITRA Installs ... Product-Method suitability consultation. I have NEVER made a mistake, I thought I did once...........but I was wrong! - PRODUCTS ADVERTISED WITHIN MY POST ARE NOT ENDORSED BY ME!