My terrace house have 2 toilets upstairs, both have leaking problem and cause the lower floor ceiling having cracks and rust. Pictures below are not mine but they look similar.

A contractor told me this can be done by completely hack away and redo the floors of both toilets, add in water prooving. But this method will create a lot of havoc. I also heard of the new nano technology but don't know much about it.

Can sifus help me make a decision: traditional method / nano?