tile over floor tiles

[aflemi]

I'm starting a hall on Monday 2.5 x 7.5m. Will be laying herringbone pattern like attached pic. Hall was originally 2 rooms, now knocked into one, 2/3 is tiled, rest is wood flooring on solid floor. Levels are not great, where tiled part meets kitchen the last 400mm or so slopes up 25mm to meet kitchen floor level exactly. Cust wants same 'no-step' join (although I will leave an expansion gap). This means I have a heck of a lot of slc to pour to bring it all up to same level. I will graduate slope over whole length of floor so is straight but not perfectly level, which I need with the herringbone pattern.
I was thinking I could leave most of the existing tiles down as I really need the height. Plan is to clean thouroughly, mapei ecoprime?, slc then tile over.
Should I put slurry coat over tiles before slc ?

 

[Gazzer]

If the tiles can not be removed and I would strongly suggest to do so, then abrade the tiles with a cup grinder next Mapei Eco Prim Grip primer and then tile.

 

[DHTiling]

You don't need to abrade with Eco prim grip , IMO those tiles would be coming up for the best guarantee. Not a lover of tile over tile.

 

[aflemi]

Ideally I would remove but if so, I need to raise floor height by average 12-15mm which, if slc'd, would mean a 25kg bag for each mm. Very expensive and time consuming. Is a viable alternative doing the bulk of it with fast setting sand and cement screed, then slc the last few mm? Otherwise, I think she may have to be persuaded that a step is inevitable

 

[DHTiling]

You could use marmox boards for the height build up, saves a lot of money on SLC.


PHG Wet rooms have these at great prices . http://www.tilersforums.com/tanking-wetrooms/62181-marmox-boards-phgwetrooms.html

 

[aflemi]

Was looking at Ardex A35 Broken Link Removed
Advantage is I can grade the fall down from the kitchen doorway to the 15mm minimum depth at other end and could tile next day. Obviously not the insulation properties but that wasn't a concern.
Has anyone used this and have advice/opinions?