Tile over old plaster walls

[askme233]

I am updating a shower in a very old house. While some of the walls are reall 150 yo plater over lathe, the shower area seems newer and the walls are probably start of the century. They are made up of a paper over plaster board that looks like it pre-dates drywall, then build up with a rough coat of cement, then a finish layer of fine white plaster (all laid up by hand).

On top of this I want to place 12x marble tiles for the shower surround and I am loathe to build up the walls with yet more backer board as it will look quite bad having a transition from the bathroom wall into the shower surround.

Can I use a penetrating sealer, then skim coat, then apply tile to keep enough water out of the walls? they seem quite water resistant already and I have a peice I am doing a soak test on now.

All help appreciated.

ASK

[bbcamp]

If the walls are already pretty square, flat and plumb, you could install Kerdi over the walls, then tile on that. Just make sure your surface is clean of any soap, oil, or lotions that could interfere with the thinset.

[askme233]

Now all I have to do is find the stuff. I think it was mentioned somewhere on this board...

ASK

[bbcamp]

Go to our online store, click on the TileExperts.com link. They'll sell you exactly the amount you need, and we'll get a nickel or two to cover our expenses