The waterproofing of a shower or bath starts with a water-resistant grout. It’s called epoxy grout. The grout is what is found between the ceramic spaces. Unfortunately, most contractors do not use it and prefer standard grout. Easier to apply and less expensive, but the mistake is that standard grout is much more porous. Over time, water infiltrates, penetrates through the grout joints, which quickly causes water infiltrations. Then mold problems occur. The water ends up being trapped between the supposed membrane inside the walls and the ceramic, as shown in the videos below.

Then the second thing to do to prevent water infiltrations and surely avoid many problems in your bathroom is to properly do the caulking joints, the silicone joints. There are several important places not to forget for good waterproofing of your bath and shower. Doing these steps well is the solution to save you a lot of mental and financial worries.