Its caused by dampness. The only solution to this is to strip your shower completely, tiles and old waterproofing (if any) and re-waterproof the shower and retile. I also recommend changing the shower trap and waste pipes along with the shower water pipes if one can afford to do so. Rather do the job once properly.
Behind shower valve handle and trim plate
No you not have to put backer board behind the tub below the shower stall area. You only need to use it behind the walls of the shower stall.
fu....ck off
Thank you for coming to the shower for Sam and me. (Both "Sam" and "me" are objects of the preposition "for.") It would be better to say . . . the shower given for Sam and me.
1- plugged shower head 2- defective diverter
Cut out the drywall in the wall behind the shower. Replace the valve. Patch the drywall.
The benefits of contemporary shower curtains is to keep water from coming out of the shower onto the floor. These curtains are also used for show in model homes.
By opening the walls
YES!
Usually you cut a hole on the other side of the wall behind the shower. Very often this is in a closet. If not, you can use the piece of sheetrock to make a door or put it back in place and retape the joints.
Simply when the temperature outside the shower is less than inside the shower the person would feel colder than when they were previously in the shower.
The benefits of contemporary shower curtains is to keep water from coming out of the shower onto the floor. These curtains are also used for show in model homes.