It's a shame you resort to insults. It just undermines any credibility you may have had.
I know exactly what is involved in lifting t&g floorboards and replacing with 25mm WBP because I've done it in my last house.
The floor in the bathroom in this house failed because the combination of the floorboards and 6mm ply wasn't stiff enough and the floor flexed.
oSB and chip board are just not suitable as a substrate for tiles because they are not stiff enough and because they are not a suitable surface to bond the tiles to. The actual surface of the board that is bonded to the tile can seperate from the rest of the board as the board flexes.
If the OP doesn't want to lift the boards hew old be better to use a proprietary tile backer board.
I know exactly what is involved in lifting t&g floorboards and replacing with 25mm WBP because I've done it in my last house.
The floor in the bathroom in this house failed because the combination of the floorboards and 6mm ply wasn't stiff enough and the floor flexed.
oSB and chip board are just not suitable as a substrate for tiles because they are not stiff enough and because they are not a suitable surface to bond the tiles to. The actual surface of the board that is bonded to the tile can seperate from the rest of the board as the board flexes.
If the OP doesn't want to lift the boards hew old be better to use a proprietary tile backer board.