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Loft cinema room soundproofing

Roberto1975

Standard Member
I am finally getting round to converting the loft space. Starting off on the insulation, for heat loss, and then sound proofing. House is near busy road and would really appreciate sound proofing ideas. I have started with 50mm of celotex between rafters, and have extended rafters to add Rockwool RW5 75mm followed by 15mm acoustic plaster board. I am thinking of then adding some sound dampening panels. Just wondered if anyone has had a similar experience?

loft is 6.4M long and 3.2M wide, although due to the pitch of the rafters, it does mean that I only have 2.5M width at a height of 168cm, so my screen is going to be low, but I’d rather go with a frameless screen and get approx 240cm wife. The whole room will be very dark anyway.

It will be ultimately running an arcam 550, apex A40 LCR, A10 rears. I’ll be looking for options for atmos in ceiling shortly.
Projector JVC X7500, also looking for new screen, Needs to be acoustic transparent 240cm wide.
Plenty to be getting on with anyway.

main issue at present is making sure it is sound proofed well. I could put 2 layers of acoustic plasterboard if necessary? Any advice appreciated 👍
 

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Wil S

Active Member
^ that's a tall wife.. (240cm).

But seriously, be careful with your insulation layers as that roof membrane doesn't look breatheable so it'll need a ventilation layer to avoid condensation.

As for soundproofing, it's diminishing returns, but two layers of plasterboard is definitely a good idea, better if you can acoustically decouple with green glue or similar. As deep as you can afford without compromising on headroom will be better for soundproofing.
 

Roberto1975

Standard Member
Thanks for that. The original rafters are 100mm and I’ve started putting 50mm celotex between them leaving A 50mm air gap around the whole roof. From what I could pick up on line it seemed that this would be sufficient for ventilation, but I’m certainly no expert so any tips appreciated. I’m actually in the loft cavity now, filthy job but the finished job will hopefully make it worthwhile 🙏
 

Wil S

Active Member
50mm air gap is fine, but make sure there's an air path from top to bottom (or the other way around) or you'll get the condensation- it's all about allowing the air to move and vent.

Good luck with it, will keep an eye on the thread.
 

edd666999

Well-known Member

Roberto1975

Standard Member
Thanks, this is work in progress. I’ve been thinking about using a layer of MLV over the studwork, then putting on lengths of resilient bars, then attach the plasterboard. This would only add about 18mm to the structure, so not to bad. I’d have to screw the resilient bars through the MLV, but it looks like that’s ok from the installation instructions. The alternative would be to put the bars to the stud work in line the back of each plasterboard as it goes on. I can only get 1m. By 1.2m boards up the loft stairs, so a fair bit of cutting and sealing to be done.
 

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