I live in a flat in London and the neighbour downstairs smokes weed constantly in his bedroom and living room! The smell comes up into my flat very easily, sometimes when he's adamant that he's just had the stuff out but hasn't actually been smoking it.
I don't know whether the smell's getting into my flat through the floors or pipes or some other way. I have wooden floorboards that were here when I moved in and are pretty old and creaky, but can't really tell if the smell is stronger down near them or not.
I'd like to have some repairs / sealing done in my flat to address the smell, but what sort of tradesman do I call to find out how it's getting in in the first place? Would a flooring company be able to tell if the floor construction below the boards is "leaky" or do I need a general builder?