Loft extensions and music rooms

[James]

To get really good isolation from the bedrooms next door will take a bit of thought within the design of the project. The main issue is that it's difficult to get enough mass in place to easily provide a lot of isolation at LF; you find that the isolation of drywall drops off a lot at LF; and most especially because good acoustic isolation is straightforward to design but naturally remains very sensisitive to detailing and workmanship on installation.

For example, addressing one point aleready raised in thread: one simple trick to help before over-lining lining walls (with independant linings) is to use a parge coat - a base coat of gypsum plaster 6-8mm thick simply to seal the base masonry on party walls (esp the joints where mortar is often missing/poorly placed). When you are looking for 50dB+ of separation a hole the diameter of a pencil can measurably spoil the results...

When I "designed" the layout of our house, one of the gambles we took was locating my music room next to our bedroom. I figured that we won't be listening to music and trying to sleep at the same time. Nonetheless, I wanted to sound-proof the drywall-lined partition as much as possible.

The wall is standard 4x2" timber framed. The main difference was acoustic insulation (Pink Batts Silencer) within and a double layer of plasterboard on each side. Nothing special was done to the ceiling (which has standard thermal insulation) or floor, which is carpet over concrete. The result surprised me. When listening at a civil level in the music room, you'd be hard pressed to tell from the bedroom. But when cranked up to as loud as I'd ever listen, there is a tiny bit of bass leakage.

For our purposes, it was more than adequate. If I had neighbours demanding absolute silence, then I suspect a double, decoupled wall might do a much better job.

 

[martin clark]

It would, and with a party wall, an independant stud lining would be the way to go. But even then - it remains dependant on very precise details of workmanship around the edges, particulary for small wall areas (because proportionally you have more linear metres of bridging edges/supports to face area)

NB picking-up something else here and there in thread - PIR foamed insulations are much better-performing than mineral wool thermally - roughly half to one-third the thickness for required performance there - but offer nothing useful for acoustic-control purposes (foil-face = non-porous = no resistive absorption). Mineral wool for acoustic control wants to be in the range 30-50kg/cu m, quite dense, so thermally not the best. Something else to think about, a mix and match is the right answer selected on requirements by location/direction.