Bathroom tiling on painted pasterboard

[linus1]

I am a new home owner and a tiling virgin. Before buying the house the bathroom had a new suite installed and was redecorated (on a budget). There was no shower and as a result the only tiling was about a foot high, running all around the bath.

I have had a shower installed and now need to add to the existing tiling, running it up to the ceiling, and I am after some advise. The walls are plasterboard and have been painted, I don't know if proper bathroom paint was used. I have read around forums and my understanding is that i need to seal the walls to waterproof them before tiling, does it matter that the plasterboard is painted? do i need to score the walls? can i use a 2-in-1 product to seal and attach the tiles or is it better to do them separately? any products you can recommend? and also, after tiling how long do i need to leave it before using the shower? any help would be much appreciated.

 

[linus1]

One more thing - a large square was cut of of the plaster board and then refitted (in order to install a shower). what is best to seal the joins before i tile - plasterboard tape? thanks for your help.

 

[JayS]

This is what you need. You'll get problems with the original tiles though since they won't have a tanking behind them the grout will leak!

 

[linus1]

This is what you need. You'll get problems with the original tiles though since they won't have a tanking behind them the grout will leak!

Thanks JayS. Is there anything i can do to seal the existing grout or slow down the leaking? And are we talking months or years before i run into problems? (wondering whether its worth pulling them all off and starting from scratch!)