Raising floor and tiling over existing floor tiles

[petey]

Hi folks.

I have some existing ceramic tiles on my tiny bathroom floor, and I wish to tile over them with new tiles. I realise the usual advice is to pull them up and start afresh, but I want to lay over the existing so the height of the new tiles will be perfectly level with the adjoining hallway, which has had a wooden floor laid down. The floor underneath the existing tiles is concrete.
New tiles are 450 x 450 and I have brought a flexible powdered adhesive.


A few questions:

1) How should I prep the existing tiles. Do I need some kind of sealant or will just a wash-down suffice ?

2) There were no tiles installed where an old shower tray was, so I need to use some kind of levelling compound to raise the floor in this area - its approx 10mm.

Can anyone recommend the best product for this situation? (Hopefully something that dries quick as I would like to tile the floor as soon as poss)

Thanks Guys!

 

[macten]

So long as old tiles are nice and secure then simply wash down with sugar soap to degrease. I also score the tiles for added key.

The other guys will recommend a suitable SLC to raise the area of the shower but you could use a cement board.

 

[Burnsy]

Agree with Macten. If you have any spare old tiles, then lay these in the shower area and tile over these.

Otherwise, cement board or a levelling compound.

Alternately, you could rip the lot up and then lay cement board (10mm) over the whole area.

 

[The Legend; Phil Hobson RIP]

All good advice above, if you decide to tile over score surface as said. Maybe a slurry bond to help key