Replacing free standing bath tub to Shower room

You can dig two vertical channels on the other side of wall where the shower mixer will be installed. You will then extend under the floor the hot and cold water pipes and run them up in the channels to where the mixer will be and obviously you will drill two small holes to bring the pipes back in the bathroom. The holes will be covered by the mixer cover and the chanels filled with rendering and skimmed. Pipes in the channels should be insulated.

Hello vai_73, assuming the bathroom walls are tiled full height all around you stand no chance to hide the hot and cold feed pipes for the shower valve. However this might work to your advantage, especially if you like rustic style, I recommend going for exposed copper (or chrome) pipes with manual valves, check this out: https://www.pinterest.co.uk/pin/536139530620261086/ Drainage being on the floor should be straightforward to connect, mind you might need a riser kit for the shower tray to create enough space for the shower trap (slim).