Precautions For Shower Room - How To Prevent Water Leakages

Good day everyone.

Kindly advice on the precautions to be taken when building a wet room (shower room) in a house.
In the house I live currently, the wet room soaks the wall of the room directly below the wet room on the lower floor.


Please advise on how to properly construct a wet room to prevent such leakage and how to rectify this current situation.


Thank you.