This job was in Carson a. A customer from a previous job asked me to waterproof a new bathroom installation because of a leak that had gone into the IT room below.
Whenever someone installs a toilet there is a question of whether to caulk or silicon around the base. Here is my two cents. On a first floor concrete installation you should always caulk or silicon around the base of the toilet. This isn't necessary but it looks nicer and iof the ring ever fails you have a second line of defense.
On a wooden sub floor you should never caulk or silicone around the base because if the ring fails water will be trapped and hidden in the sub floor and will cause damage even if there is water proofing. End rant.
On this job there was a lightweight concrete deck on top of a plywood sub floor. In order to water proof this we used a product called hydro ban. Hydro ban will waterproof a solid surface by merely painting it onto the surface. Judging by the condition of the existing concrete I could determine there was no cracking or deflection in the floor. If the floor is flexing this need to be corrected before attempting to waterproof.
A plumber had just installed floor drains before we came. It was obvious that any water leakage was around the toilet flange or where the floor meets the wall as naturally there is a small seam at these points. We used a cloth fabric designed for water proofing to cover these points plus the new floor drain and create a completely solid surface to water proof. Then we gave the floor two coats of water proofing material.
Now all the need to be done is too make sure the tile installers do no carelessly or purposely scratch the floor when installing the tile.
This method will stop minor flood or leaks. Obviously if water runs out from the restroom into the hallway the water proofing stop at the threshold of the restroom door.