Loft conversion sound isolation advice

skeediddley

Standard Member
Hi all.

I am about to embark on a loft conversion in order to build a private music studio for myself as I am a composer by trade and would like a space to work in from home. I also play drums so I would like to limit the amount of sound escaping from the room, principally to avoid disturbing my neighbours. Luckily I am in a detached property, so I have a head start, and UK building regulations for loft conversions also guarantee a good minimum noise pollution requirement. I have also had the good fortune of finding a small independent loft contractor, who understands my requirements and is keen to help achieve them.

After much deliberation over which sound isolation techniques should be employed to further reduce leakage, I have narrowed it down to the following plan to suit budget and practicality.

I will be converting my loft space to the maximum permitted size of 50m3, with a 6 meter Dormer section and then creating a symmetrical 4x5 meter room in the middle of that space, which will be used as the main studio, with an annex room off to one side, and the stairs and a shower room to the other.


Floor:

New steel structural beams will be installed directly into the walls and a new suspended timber floor will be built. This will be insulated in accordance with current building regulations with 100mm glass wool, and covered with 22mm tongue & groove decking sheets. On top of this a further 22mm Isomass 24T acoustic flooring will be laid.

The fact that the floor is suspended will hopefully cut out a lot of direct transmission noise, and will also form a natural mass,air,mass two leaf barrier. Once the room is finished I will probably look to see if I can add a further decoupling by the form of some rubber matting underlay and carpeting.


External walls:


External walls will be constructed using 100mmx 50mm timber, insulated with100mm glass wool and clad on the exterior with tiles. On the inner side of the walls I will employ a resilient channel system to decouple the two layers of plasterboard. For a far better description visit here:


studio-wall-soundproofing-system.html


I will not be however, sandwiching a layer of soundproofing mat on the external walls as I will be reserving this for the inner structure.





Ceilings

The ceilings will also be constructed in the same fashion as the walls with a resilient channel system, and two layers of plasterboard. However, this time I will be sandwiching a 1.2 mm thin rubber soundproofing mat to help decouple one layer of plasterboard from the other. This entire area will be sealed with acoustic sealant and then skimmed with a layer of plaster.






I am hoping that the resilient channel system will act to decouple the double mass plasterboard from the studs and thus the walls and ceiling, and hopefully cut down on any flanking noise transmission to the rest of the house and the outside would. Also the shortest path for the sound to follow and therefore the weakest link in this chain is the ceiling as it will be the closest to all sound emitting devices and not protected by the thick cladding I am proposing for the inner partition walls which will encase the main studio. For this reason I chose to divert the extra rubber matting to the ceiling as opposed to the external walls.

Internal partition walls.

As I mentioned before, I wish to create a structure in the middle of the enitre loft area, with other rooms flanking it on either side to create a natural buffer to the houses either side of me (even though I am in a detached house, I still have neighbours!) For this reason it is crucial that the partition walls do a lot of the work in decreasing the decibels. To this intent, the internal partition walls surrounding the main studio will be built to a two leaf mass, air, mass specification. They will be constructed of timber stud work which will be isolated from the floor and ceiling with EPDM foam rubber, and will essentially be two partition walls built in parallel with a 100mm gap in between the two. They will be clad with the usual two sheets of plasterboard in between which I will also sandwich a 2mm sheet of a heavy layer mineral loaded soundproofing mat (SBM5). This will be done on both sides of the wall and should end up with a wall cross section reading as follows.

12.5mm plasterboard, 2mm rubber mat, 12.5mm plasterboard, 100mm glass wool insulation, 100mm air gap, 100mm glass wool insulation, 12.5mm plasterboard, 2mm rubber mat, 12.5mm plasterboard.

The plasterboard will not touch the floors or ceiling and the remaining gaps will be filled with acoustic sealant before being finally skimmed with plaster.

Doors & Windows


Sadly I will need to get in and out of the room, and will also be requiring light, so I will be forced into installing 2 doors, a Juliet balcony (a Double glazed laminated glass, rubber sealed, PVC framed set of doors) and a couple of velux windows into the space.


To minimise the pain of having to cut holes in beautiful airtight double thick shell, I will be using a double door system for access to the studio, and acess to the annex off of it. So two sets of standard FD30+ fire doors will be hung with particular attention taken in making sure they have an airtight a seal as is possible.


Luckily, the velux are available in a triple glazed format with laminated glass and good quality seals, So I am hoping they will be enough to not need to install a further fourth layer of glazing immediately, thus negating their open-close function. I will leave ample space in the design to be able to add further glazing should it be required at a later date!

As for the Juliet balcony doors, they are also designed with sound isolation in mind to comply to building regulations, but yet again, should they fail, I will leave space for them to be covered by an inner sliding glass door.


Electrical


The main room will need 6 down lighters in the ceiling due to the reduced head height, and so the ceiling will need to have holes cut in them (aaaargh), but this necessarily evil can be counteracted to an extent with realtively cheap acoustic downlighter hoods, and careful filling. Or should I opt for uplighters n the walls instead? (its all holes I suppose)

Studios also need some wires to be run behind walls or under floors, so I plan to run a 16way 3core cable loom from one end of the room to the other and from the main studio to its annex. So sadly I will have to poke at least 2 further 50mm holes into the sides. Other than that, all electricity and network outlets will be surface mounted.


Questions?


The questions, I suppose are – Is it in any way under-specified? Or is it indeed over-specified for my use? Is there anywhere where I am just flushing money down the toilet? Or is there anywhere where a small extra investment could perhaps improve things? Have I covered all bases or am I missing the plot anywhere?

In particular what are peoples thoughts on the rubber membranes I am planning to sandwich in between the plasterboard? Worthwhile or fools gold?


And finally, how could I improve on this? Any suggestions? and is it going to work?


Thanks in advance for any advice. :smashin:


Al
 
Last edited:

Amioa

Novice Member
looks ok, i might be tempted to get an acoustic flooring system too if possible, dont forget acoustic sealant for all holes you make and for the edges. Id look at other methods of damping, MLV is good, but is it the best you can do? A bit more research there before deciding.
 

skeediddley

Standard Member
looks ok, i might be tempted to get an acoustic flooring system too if possible, dont forget acoustic sealant for all holes you make and for the edges. Id look at other methods of damping, MLV is good, but is it the best you can do? A bit more research there before deciding.
Thanks very much for your input.

Do you think that perhaps Green glue could yield better results than mass loaded vinyl? I have never come across it in the uk, although I believe it is now readily available. I would imagine the cost of MLV and Green glue would be very similair.

Cheers
 

Amioa

Novice Member
best place to check comparison data for gg and MLV would be the green glue website, but also hav ea look around at other tyes of mlv sheet to see if test data from all sources. Prices will really depend on what you get, if you go for acoustiblok it is more expensive than similar mats from custom audio. work out the price of GG as 1 tube to cover 1.44sqm.
 

skeediddley

Standard Member
best place to check comparison data for gg and MLV would be the green glue website, but also hav ea look around at other tyes of mlv sheet to see if test data from all sources. Prices will really depend on what you get, if you go for acoustiblok it is more expensive than similar mats from custom audio. work out the price of GG as 1 tube to cover 1.44sqm.
Thanks very much for your help.

After more research I have decided to go with Green glue throughout instead of MLV. Cost wise, it is equal to MLV but it works out cheaper if you factor in the reduced installation time.

This way round I can actually afford to dampen all the walls (external, partition & ceilings) rather than just a select few. I would imagine this will all make a difference.

Cheers
 

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