Bare room - sound proofing options & opinions please.


Prominent Member
We had an extension built 12 years ago, and I have been doing all the internal work. I have finally got to the last room, which has been my workshop until now, and is going to be our home cinema/family room.

Currently it is a bare brick room, the walls are thermalites, and the floor is a concrete slab (which extends under a wall, the cloakroom and utility room), which is about 130mm below finished height. There is a pair of French doors in one wall, and a large window in the front wall. Dimensions are approximately 4.5 by 4 meters. Current height from finished floor level to the bottom of the floor joists above is 2335mm, so can't afford to lose to much height. The room mainly sits on it's own with three external walls, the fourth wall has the utility room, clock room and hall way, the kitchen slightly over laps on the rear wall. Above the cinema room is our bedroom, this has 3 layers of SBM5 sound proofing mat, Cloud 9 Cumulus underlay and a nice thick carpet. All gaps around the floor perimeter were sealed with soundproofing mastic.

I'm the only man in the house, I have two daughters and what seems to be a typical wife (would be happy with a 32" TV in mono!) so I need to keep noise to a minimum. With this in mind I'd like to minimize flanking sound as well.


This is what I've come up with after much research.


Build a floating floor which is sat on rubber pads. The rubber pads are what's left over from an anti vibration pad I purchased, this is 20mm thick. I would build a subframe out of 63 x 38mm timber, this will be sat on plenty of pads to spread the load as the timber is not substantial, then boarded with either 2 layers of 12mm ply overlapped or one layer of 25mm ply. The voids will be filled with fibre glass loft insulation. I will also use some of the rubber pad around the perimeter as a spacer to give 20mm clearance from the walls. This should give me the correct floor height to match the hallway once the underlay and carpet are down. It should also decouple the floor from the concrete slab.

For the ceiling I have found this Genie clip system, which uses 100mm 60kg/m3 density insulation between the existing joists, then the Genie clips and furring channel and then two two layers of 12.5mm acoustic plasterboard. The gap between the plasterboard and thermalite wall will be sealed with acoustic mastic. I will use green glue between the two layers of plaster board. Lighting will not be installed in the ceiling, I will put LED lighting in a pelmet around the perimeter, and possibly some up lighters on the walls.


Build 50mm metal stud work walls, fixed to both the floor and the ceiling furring channels, 10mm clear of existing block work. Use 50mm rock wall insulation to fill the void. One layer of 19mm plywood and two layers of 12.5mm plasterboard with green glue between all three. Total wall thickness 104mm, so a loss of about 210mm room width.


I've not done much research on doors, but I want to keep the existing door as it matches all the other downstairs doors (and I doubt SWMBO would let me change it anyway). The problem is it's a cheap pine glass panelled door. I thought of perhaps getting a double glazed sealed unit made (just the glass bit) and a wood frame and fixing this to the inside of the existing door, and of course fitting some seals around the door.


  1. As the concrete floor slab has a DPM and 100mm insulation under it I presume I don't need air vents under the floor like a normal wooden floor would require, is this correct?
  2. I haven't thought about how to do the window and door reveals, but I expect these will just have to be plaster boarded, I'm open to suggestions.
  3. Is any of the above going to adversely affect room acoustics?
  4. Which would be better in this room, 5.1,5.2,7.1 or 7.2?
  5. The above is obliviously going to cost a lot, but at least the labour is free, so will the outcome be worth the effort and expense?
I found this website full of useful information, so I list it here for others and my own future reference.

I'm a very competent DIYer, although I prefer the term self-builder ;-) so the work doesn't phase me once I know what I'm doing is correct. A full cinema build thread will also be started of course :)

Thoughts and advice on the above please.


Established Member
Sounds like you know what you're doing and it's going to be great.
I can't advise about soundproofing unfortunately but I wish I was in the position to be able to do this type of treatment. It will definitely be worth the effort as you will be able to enjoy the system without worrying about noise outside of the room.
I don't think anyone can advise you regarding whether 5.1/7.2 will be best as it is personal preference. I would be happy with 5.1 in that size room but I would definitely wire for additional speakers at the construction stage to give you flexibility.
As for room acoustics, again, hard to advise other than to say yes this will definitely have an impact on how the system sounds. A lot of information is available on the acoustics thread. The room can always be improved with treatments post construction.
Good luck


Prominent Member
Thanks for the feedback pinppong. I shall certainly run in enough speaker cable to allow for a 7.2 system. So many things to think of I end up with information overload.

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