Tsk, tsk, Unit Dweller, you managed to commit two cardinal Forum sins in the one posting. First you created a new topic when the existing thread (this one) would have done perfectly well. Then (shudder) your headline was only a couple of words shorter than the post. But we are very forgiving here at Flat Chat, so consider yourself absolved … this time.
To answer your question, I would avoid any prescriptive by-law that sets a minimum standard for the floor because that can’t take into account all the variables, including the thickness and density of the slab, the acoustic properties of the building or, indeed, the behaviour of the occupants. I would favour something like:
Owners may not put down, create or change the floor covering in any way so that it provides less sound insulation than would be provided by wall-to-wall carpet professionally laid on top of a high grade underlay.
Any owner who does so, causing any increase in noise transmission to any other unit will be required to immediately restore the flooring to its previous noise insulation properties at their own expense.
Now I’m not a lawyer – and I’d be interested to hear from someone who is – but I reckon that puts the onus on the person changing the flooring to make damn sure they have the very best materials and if they are stupid enough to believe Dodgy Dave from the Floating Flooring Emporium that 3mm of plastic will “do the trick” then they deserve all the grief that will doubtless be coming their way.