I live in a ground floor flat in a converted terrace house, (conversion done in 1970’s). The sound insulation is poor. I am an owner occupier but the upper flat is now a “buy to let”. What was originally a 3 bed maisonette has now become a 4 bed by using the reception room as a bedroom. The kitchen, which is directly above my main living room, serves as the only reception room for up to 8 students. The landlord, has now fitted laminate flooring in this room. My Council have refused to help as both flats are privately owned.
If you have “poor” sound insulation but the conversion was carried out according to the standard of the day (correctly at the time) then you need to determine whether the activity of the occupants is unreasonable or not. Individually it might not be but collectively this sounds like a concern. If the noise impacts substantially on sleep during nightime hours (11pm-7am) it will be much easier to establish nuisance. If this is the case there may be health and/or wellbeing impacts and the Council will have a duty to act. There are also human rights implications. Whatever happens the Council have a duty to investigate. Depending upon the answer to the above questions you might consider challenging their decision not to investigate via their complaints procedure. Make sure you are talking to the correct department – usually environmental health. The fact that the properties are privately rented makes no difference as to whether the Council take action or not.