[dgun357]

I started a remodeling project in the entry way of a 17 year old house. The current floor is ceramic tile, which receives heavy traffic, and is outdated but by all rights still well adhered. When I started demo, i expected to see some sort of plywood or cement board, since tiles were not popping or cracking. What I found was particle board (it is definitely not OSB or plywood).

Since the concensus is you cannot tile directly over particle board, why is the current tile holding so well (it is original). The adhesive appears to be standard gray thinset.

My other question is: would i be better installing the new tile over the existing tile (if yes, best method?) since there are no loose or cracked tiles currently? Or, should i continue to tear up the existing floor, then install cement board over the particle board. Both options raise the height of the new floor about 3/8", so as far as that goes i see it as a wash.

[ididit]

Yea sometimes it works but most of the time it dont. Take for instance a house I know of built in the mid 80s on stilts 8' high (flood zone). The joist are 2x8 spaning 14' and 16"oc with 7/8" osb subfloor nailed and not glued. The kitchen was originaly vinyl then a few years later different vinyl, a few more years vinyl tiles and then again later ceramic tile were laid using a mastic.Every layer on top of the last. It goes against everything a tile man knows but the tile have been there about 15 years now and not a crack in tile nor the grout! Go figure.
In your case if your where to disregard that its fine now and go ahead and redo it right that would mean ripping the floor up down to the joist. Make sure they are not spanning too far per joist size, and add neccessary blocking. Glue and screw down 3/4" ply, thinset and screw down 1/2' concrete or hardy board then thinset down the tile.Your doors will clear this arangement. There is a new product that rolls out called ditra that takes the place of the concrete board you might check out too.

[firehawkmph]

Even a broken clock is right twice a day. It's like a guy 92 years old, smokes all his life and doesn't get cancer. Sometimes it's just dumb luck.
Mike Hawkins

Since the concensus is you cannot tile directly over particle board, why is the current tile holding so well (it is original). The adhesive appears to be standard gray thinset.