Acoustic wool is better than loft roll or whatever. It's the density that matters. We put it in the first floor and in all internal walls and are very pleased with the results. It shouldn't fill the space, there should still be some cavity left.

We also put resilient bars under the joists before attaching the plasterboard, and on the walls of bedrooms.

We have carpet and underlay in our bedroom and on the upstairs landing so I didn't bother with any impact reduction sheets on the floor, or doubling the plasterboard underneath. We had quite a lot of plasterboard offcuts, so we glued all those inside the stud walls of the bedrooms to increase the mass, using AC50 glue.

Hi,

Thanks for your response. I’m not familiar with resilient bars but I’ll look into them and I’m sure my builder probably is. The ceiling downstairs is being over boarded so hopefully I can use them there.

When you say some cavity left is there a number I need to think of? I was thinking of 100mm Acoustic wool but perhaps I should go for 50mm? Any good brands to look for?

Does the acoustic wool add much to the thermal characteristics of the building? I’m installing a log burner in the living room and I don’t want to over heat.

I’ll look into the AC50 glue too.

Thanks very much.

150mm rockwool sound insulation batts.

This sound insulation would normally be a requirement for building regulations approval

Part E has sections E1 and E2. One is for walls and floors between separate dwellings and one is walls and floors between rooms in the same dwelling.

I know they apply when converting one house to flats. Not sure if they apply when converting a loft to a new habitable room or when partitioning one room into two.

The resilient bars do far more to reduce sound transmission than the acoustic wool in my experience.

I have used them on a stud wall and in ceilings, and in both cases the sound reduction is impressive.
The ceilings have a single layer of 12.5mm plasterboard hanging off the resi bars, the stud walls have rockwool in between the studs, resi bars on the studs and two layers of 12.5mm plasterboard on the resi bars.
It is important to install them according to specifications:
http://www.soundservice.co.uk/installation_resilient_bar.html
The cost of the resi bars is very little. Your builder might charge a bit more for installation and there is the cost of additional layer of plasterboard when dealing with walls. All in all not much for a lifetime of serenity.

@nigel: if that were the case, resi bars on walls would not make sense in any case.
The resi bars and double plasterboard form a mass-spring system, with poor transmission properties for a wide spectrum of audible frequencies. That is why they are used to acoustically decouple rooms from their surroundings, for example for recording studios or music rehearsal rooms.

Posted By: bhommels@nigel: if that were the case, resi bars on walls would not make sense in any case.
The resi bars and double plasterboard form a mass-spring system, with poor transmission properties for a wide spectrum of audible frequencies. That is why they are used to acoustically decouple rooms from their surroundings, for example for recording studios or music rehearsal rooms.

To make a difference to sound transmission ie loud voices/music next door you would need to achieve approx 50db sound reduction.
You would never achieve that with resilient bars and two layers of plasterboard.

Posted By: Rick_MThe building debris I've seen used between floors in older properties seemed like a cheap way to get high mass with no gaps.

That's certainly the case in my old house, where the gap between ceiling and floor is completely full of what looks like tightly packed sawdust. No fire risk there then.... :( That said, I'd say the thick plaster over lath and thick floorboards also help. It doesn't make any difference in my case though as the sound just bounces around the open hallway and up the stone staircase to make its way upstairs!


From what I know about the transmission of sound, a combination of different materials is probably the best way to approach it. Different materials are effective at blocking different frequencies. If you are trying to block normal conversation levels and low level TV noise you would probably approach it differently to a room with a sound system with a sub-woofer. For the former a bit of rockwool or loose fill in between, and carpet upstairs, or thick underlay under solid floor is probably enough, for the latter it can get tricky.

I might be stating the obvious, but in the example of my house above, very little sound travels through my walls and ceilings, but it passes straight through the hollow door and the gaps between the doors, and upstairs via the hallway. In my experience its often the door that is the weak point in keeping sound in and out of a room.

As there should be no air gaps between floors its mostly about deadening the mechanical transmission of sound. The following is a bit involved but has some example diagrams of floor construction that might be helpful:
https://www.mne.psu.edu/lamancusa/me458/9_trans.pdf