Flooring Tile - new tiles on old green board

I am in a project of replacing bathroom shower pan. In order to do that, I have to knock off its surrounding tile walls. I found underneath those tiles are green board. I plan to replace the one in the bottom part connected to the shower pan with those Hardybecker and leave those upper part intact.

Now my question, can I tile over these old green board with new tiles? As I stated above, because the old tiles on the green board were removed that left the surface of the board not even. As a matter of fact, the green color of the board were gone, there are brownish paper/clay like material on the surface. Can I tile on it? Thank you very much for any advice.

John

Replace all the greenboard inside the shower surround with 1/2" cement board and while you are at it put up a sheet of 4 mil plastic over the wood studs to keep them from rotting out should any water finds it way back there in the future. Greenboard has been decertified for use in tub/shower surrounds by the old BOCA code people, now called IRC. That green paper was the only water reistance on the wallboard so if that is gone you have plain old shetrock hanging there, bumpy old sheetrock with mastic I bet that also is a no-no inside the wet area because it re-emulsifies when it gets wet. Tiles have a nasty habit of falling to the floor when that happens. :eek: