This issue is repeated constantly on here, Dave myself and others spend ages on it...............
You have a room 5m2 with a wet room former in, it could be tuff2, Aquadec, Tilux, Showerdeck, Wedi, Pro4mer, Pro4ma it doesnt matter.
You put underfloor heating down over the entire floor then discover the former wasn't fitted level or you have a drainage problem.
At this point you have a tray former, tanking membrane, UFH, leveler, adhesive and tiles layered 1 on top of the other.
If you cut out the former which is the option you will loose the UFH for the whole room.
If you didn't put under floor heating over the former in a wet room then you are a much happier man trust me.
It is a call you have to make but imo its the correct one
Hope this explains it a little.........
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