Lay a sheet on the bathroom floor to protect against water?!

Hello. Our tiler recommended laying a kind of film in the bathroom to protect the screed from water damage in case of an incident. Many insurance companies would no longer pay without this film/sealing. I have never heard of such a thing and found nothing about it during my online search. Is what he says true, or does he just want to make money? We have planned vinyl flooring in the bathroom itself, which will be glued.

A liquid membrane is applied to seal everything. The tiler smears the substrate and the base at the bottom with it. After drying, he tiles over it.

Is this liquid membrane mandatory? So in the entire bathroom and not just in the shower? Regardless of whether it's tiles or vinyl, etc.? Of course, I can understand that in the shower.

Is this liquid foil mandatory?

For walk-in/floor-level showers, yes, throughout the entire room. Otherwise, not to my knowledge. The type of flooring doesn't matter, since none of it is waterproof.

Yes, waterproofing in bathrooms is mandatory. DIN 18534 Depending on the type of shower (without tray, with partition...), there are different requirements for walls and floors. Light and dark gray are the waterproofing areas

Okay, this is a clear overview, perfect & thank you. Can you also tell me how it would look in the event of an insurance claim? This seems to refer to the following: - Water flows from the shower or bathtub + no sealing on the entire bathroom floor = bad luck (damage will not be covered) With sealing, it would be covered unless negligent, etc. - What happens in the case of a fault/defect in the pipe from the sink or toilet if I have no sealing? Will the claim then be covered?