Sound proof loft conversion

[toshtastic]

Hi,

Im looking for ways to cut down outside noise to my loft conversion. In the loft is the main bedroom and the noise from outside can be quite annoying at times so I would like to minimise it.

I was thinking that I could put some insulation (the solid stuff that you squeeze into joists - I cant remember the name right now) between the joists in my eves, and maybe even some extra membrane/insulation material stapled across the joists.

Do you think that would work?

I think its mostly the roof that is letting the noise in, but the floor of my eves could also probably do with some better insulation. At the minute the floor of my eves has some glass wool between the eves and flooring panels over the joists (although not covering all the joist)

Does anyone have some ideas or pointers to websites that can help out?

Thanks in advance

 

[toshtastic]

wow! it would help if I could spell the subject correctly!

sorry about that

 

[freddiemercurystwin]

Avoid the solid stuff as you put it (Celotex, Kingspan etc) and stick to mineral wool insulation such as Rockwool. Is much better for sound insul.

 

[toshtastic]

thanks

so if I just fill the joists with as much rockwool as will fit (without squeezing it) you think that will make a difference?

I was thinking of that, before actually, and also maybe stapling some insulation across the joists (the thin silver bubble wrap style stuff you get) - you think thats overkill? It cant do any harm though.

Also, the wall for my loft conversion has kingspan insulation on the eves side of the room, I was thinking of covering that up with gyproc as well. You think thats worth the effort?

 

[wavetrain]

I have never been a fan of loft converstions for this reason.

Sound insualtion is achieved in the main through the mass principle in structures, therefore you need weight in the walls to achieve this.

 

[^woody^]

Rockwool will be better for sound insualtion, but you are unlilkey to have rafters deep enough to allow enough depth of rockwool to conform to the thermal insulation requirements.

Insulate with celotex/kingspan to get the required thermal values. Then underboard with a fibreboard or similar accoustic board (to provided a degree of sound isolation). Then use a sound-check plasterboard (blue).

 

[alittlerespect]

I wouldn't go throwing too much money at installing fibre insulation products into floor and roof cavities. These materials will reduce some of the higher frequency noises, but they will do next to nothing for the lower frequency noises. As already mentioned 'mass' is the answer as heavy and stiff materials are do not transfer sound so easily. You should view sound in a similar manner to water, in that it will always look for the path of least resistance to add to the problem sound also travels in all directions (unlike water). To reduce the sound coming into your room you would need to isolate the ceiling, walls and floor, and add some mass to the ceiling and walls.

As an example to isolate the floor - take up the flooring and take off the skirting boards, use a material called 'regupole' and stick the material to the face of the top of the floor joists, then stick 2x2 timber battens onto the regupole along the line of the joists (not counterbattened) AND then relay flooring (wait for it!) on 19mm plasterboard and fix to the 2x2 battens making sure the fixings do not penetrate the regupole, while you have the flooring up it would give some benefit if you laid a 100mm thick mineral fibre blanket - this would need to have a minimum density of 12kg/m3. It would also be wise to lay a thin strip of regupole between the flooring and the wall elements this will then give you a sound barrier between the elements. If you need to go one step further then consider adding a 2 laysers of 12.5mm plasterboard with staggered joints to the ceiling below - thats about the most economical means of providing insulation to the floor.

this should give you a taste of what you would need to do with the walls and ceiling in the loft space if you really want to get some meaningful sound absorption to the loft.

Regards

ps take a look at www.cmsacoustics.com for some trade products!

 

[toshtastic]

thanks for all the replies guys.

It gives me something to think about anyway. I had been thinking of using something like this :
http://www.soundservice.co.uk/acoustic_mineral_wool_AMW.html

but im not 100% convinced its all worth the cost and effort any more

thanks for all your help though

 

[jeds]

Really need to to know the construction of your loft roof to give a meaningful answer. Do you not have insulation between the rafters at present? And what sort of noise causes the most problem. Rain, traffic?

The fact of life is that you need lightweight insulation to reduce high frequency sound and higher mass to reduce low frequency sound. It is also beneficial to have an enclosed cavity of approx 200mm as well. So, you need a high mass low mass roof with a 200mm cavity. Unfortunately they don't do them at Screwfix.

 

[toshtastic]

no, there is nothing between the rafters at present. I have glass wool on the floor and kingspan in the walls - but the timber rafters have nothing between them.

The noise Im trying to cut out is mostly traffic

 

[jeds]

My advice then would be to put as much PUR insulation between the joists as you can get in - but leaving an air gap between the insulation and the underside of the membrane. Techncally the air gap shoud be 50mm but for a retro-fit 35-40mm would be acceptable. Make sure the gap is ventilated top and bottom. The insulation should then be finished with a continuous layer beneath the rafters. How thick depends on what you got between? If 100mm then a 30mm layer would be good enough. If less then I would go to a 50mm layer.

Finish with 15mm soundcheck plasterboard (the blue high densty stuff) or for better sound results fix 2 layers of the same with staggered joints.

You should also check the perimeter of the roof and eaves for any gaps. The rule of thumb is that 90% of sound will travel through 10% of gaps. In other words, gaps are bad. Fill them with acoustic sealant - but make sure you don't cut off essential ventilation.

 

[paulyp]

Hi, conscious this is an old post, but just wondered whether you found a solution that was effective? I'm currently trying researching the same issue.

Thanks!