Hi all...hope all well out there!

Here's a question for you...looked at a floor job tonight. The tiles are onto a suspended floor screeded with 50mm concrete with water underfloor heating. The floor has been down about 6 years and most of the tiles are loose. I'm assuming they are loose due to not a full bed of addy, the wrong addy, movement due to being a new build or the customer turning up the heat too soon! Retiling that part is easy enough. The main problem is that they are changing the room layout to make a new room with half the floor havinf a timber substrate and half having a heated screed. They not sure about tiling and may put down vinyl but want me to level the floor throughout that room. my thought was to remove tiles down to heated screed and remove floor boards and use ply to bring that half level to the screed, then possibly bond hardibacker or a marmox insulation board to go over screed and onto ply where it can be screwed. Obviously it cant be screwed onto the screed as I don't want to hit a water pipe. The floor size is only about 4sq mtr. Any thoughts....hope this makes sense!!

no need to lift boards in my opinion. If the timber floor is solid just install you backer board over this then screed the conrete to the same height as timber floor/ backer board and once set screed over full floor. If the timber floor has deflection I would just add additional noggins mate to strenghten it. (if its in a poor state then replace.

Will always be a chance of screed cracking at join unless you incorporate joint between both substrates.

Thanks mate...main reason I was going to lift the floorboards was because the customer wants the same height of floor throughout so won't accept a 6mm lip if I was to put the backerboard on top. Plan was to remove them (25 mm thick) then put down 18mm ply, 6mm hardibacker and skim with SLC. If he puts down vinyl then a crack will be hidden...tiling would require an expansion joint and he don't want that.