Raising a ceiling and reducing sound proof ability

[andypfc]

During a recent building project our builders suggested that we had room to raise our ceiling above the current level. Being 5'7" and easily being able to touch the ceiling we were interested. We were sold on the idea as the builders told us the sound proof level would be the same or better than before.

We live in a ground floor flat conversion. During the conversion a suspended ceiling must have been installed.

From what we saw of the job, the builders used 15mm Soundbloc board, and although having bought new insulation material, predominantly used the existing material which looked in a very poor state. It looked like the material I used to see in my parents loft space.

Suffice to say, at the end of the job we can hear normal conversations upstairs now (unlike before). We understand that floorboard creaks will always be transmitted but conversations are a no go.

We are now in dispute with our builders who say that the material's density they reused was sufficient and that from their point of view there is no change in noise levels.

The builders did indicate at first they would use 2 pieces of soundbloc board but in the end decided to go with one. From my (hindsight) view attaching the single board to the joist and using the old insulation was never going to give us the same sound proofing level as the suspended ceiling.

Having read the soundproofing projects on this website I feel they've done a somewhat poor job. And should have suggested acoustic membrane between two sheets of plasterboard, and mineral wool in the cavity.

Can anyone advise as to what I can do as we're in deadlock here. Thanks for anything anyone can suggest.