Mattress Foam (NOT memory) in stud wall as sound insulation - sensible?

[axt]

Hah, yeah I can imagine sand being a bit too eccentric even for me! Double studding is certainly a good idea and one I have seen mentioned before, but most of the studwork is existing so not really viable. There is not really a sound issue I am trying to solve, it's more of a "while I am here I may as well try and make it as best as possible" scenario. I think dense rockwool wins, and mattress Foam can go back in the loft for another use / packing.

For 3 inch wide studs, is it best to get 75mm or to try to squeeze 100mm in for even more density? I note Wickes etc often only stock 50 and 100mm thick?

Now need to work out the difference between RW3, RWA45 and all the other rockwool variants, and the best place to get a load of bales of it...

 

[Ivor Windybottom]

Soundproofing sounds a lot like hifi, probably some of the same people in both camps. Lots of waffle, self-appointed experts and psudo-scientific claims.

 

[yorksbuilder]

I was wondering if this was a good idea

No. Its a bad idea. Use rockwool batts.

 

[axt]

Yes, though what is the consensus over using rolls of mineral wool glass fibre loft insulation (which there are many available to me from failed loft top up attempts in the past by family members) manipulated into the studwork Vs the dedicated batts?

I assume the rockwool batts are more convenient as they kind of hold themselves in place but is rockwool much better than 'mineral wool / glass fibre'.

Any opinions on the rockwool standard RWA45 at 45kg/M3 Vs RW3 at 60kg/M3 or the Wickes rockwool acoustic stuff which I struggle to find a spec or part number of?

 

[endecotp]

what is the consensus over using rolls of mineral wool glass fibre loft insulation (which there are many available to me from failed loft top up attempts in the past by family members) manipulated into the studwork Vs the dedicated batts?

Heavier is better than light. Light is better than nothing.

 

[Deluks]

The RW3 is noticeably heavier, thus denser than loft roll.

 

[axt]

Interestingly, rockwool appear to do the following batts:

Wickes stuff (400mm wide, 1200 long, 50 or 100mm thick) - 35kg/m3
RWA45 - 600 wide, 1200 long, many thicknesses - 45kg/m3
RW3 - as above, 60kg/m3
RW4 - as above, 80kg/m3
RW5 - as above, 100kg/m3
RW6 - as above, 140kg/m3

I assume that the RW6 in 75mm thickness cut into 600x400 squares to fit in the studwork would be best, on the 'heavier is better philosophy' but the RWA45 and RW3 seem the most readily available... but then I do need around 40 batts so online order and delivery is viable.

I take it this is just a cost Vs diminishing returns on acoustic performance as RW6 must have more than twice the material over RW3, there is no disadvantage over using RW6 (other than cost / handling)?

 

[Deluks]

You can make the wall as 'soundproof' as you like, but the doors, windows, physical connection between the various events, screws, nails, connecting timber or framework, floor and ceiling will then become your weak spots.

It is often more cost effective to just add another layer of ordinary plasterboard than to specify a high cost insulation product.

 

[axt]

You can make the wall as 'soundproof' as you like, but the doors, windows, physical connection between the various events, screws, nails, connecting timber or framework, floor and ceiling will then become your weak spots.

It is often more cost effective to just add another layer of ordinary plasterboard than to specify a high cost insulation product.

Thanks, yes I have heard that from a few people, unfortunately I am up against it dimensionally really - though this raises another interesting point :

I am going to tile the entire inside of the rooms, and have been caught in the 'Cement Board (HardiBoard / BAL) Vs XPS (Jackoboard etc ) type tile backers'. On the basis of density, one could assume that the much heavier HardiBoard and tiles would be more beneficial sound wise than much lighter polystyrene type backer...?

It seems many online places sell the cement and a increasingly varied array of XPS type boards with barely any insight into the virtues of any of them. I believe the Hardi / cement types may need priming / sealing before tiling and may be more difficult to cut?

Too many choices nowadays...!

 

[Deluks]

What are are you intending to do in this tiled, soundproofed room, are you a serial killer! ?

 

[axt]

Haha, no it's just a bathroom but with toilet, bath / shower, water tank / airing cupboard backing onto a bedroom I wanted to make the most of the opportunity while the studs are exposed to make it as soundproof as possible. It had nothing at all before so anything is an improvement...!

 

[Deluks]

Your staggered stud, rockwool, and soundproof plasterboard will give better wall performance than 99% of domestic bathrooms in existence.

Bear in mind, it is recommended to leave a small gap when installing a bathroom door, to allow air to enter underneath, to replace what's being extracted by the extractor fan (which if you don't have, is strongly recommended)

If this is an ensuite, that little gap will let all the sounds be heard, so you'll need to fit the door accurately, use a door that's heavy enough to match the performance of the walls, and arrange an alternative way to get passive airflow into the bathroom.

 

[phatboy]

Your staggered stud, rockwool, and soundproof plasterboard will give better wall performance than 99% of domestic bathrooms in existence.

Bear in mind, it is recommended to leave a small gap when installing a bathroom door, to allow air to enter underneath, to replace what's being extracted by the extractor fan (which if you don't have, is strongly recommended)

If this is an ensuite, that little gap will let all the sounds be heard, so you'll need to fit the door accurately, use a door that's heavy enough to match the performance of the walls, and arrange an alternative way to get passive airflow into the bathroom.

A bit more cost, but a single room MHrV could be used, just needing a second hole to outside.

Then a tight fitting door would work

 

[axt]

Your staggered stud, rockwool, and soundproof plasterboard will give better wall performance than 99% of domestic bathrooms in existence.

Bear in mind, it is recommended to leave a small gap when installing a bathroom door, to allow air to enter underneath, to replace what's being extracted by the extractor fan (which if you don't have, is strongly recommended)

If this is an ensuite, that little gap will let all the sounds be heard, so you'll need to fit the door accurately, use a door that's heavy enough to match the performance of the walls, and arrange an alternative way to get passive airflow into the bathroom.

Ah, I have neither staggered studs or soundproof / foam backed plasterboard - studs and outside plasterboard all existing. Inside is going to tile backer and getting tiled. Only thing I can implement is the rockwool...

No fans as of yet, rooms both have very large windows with two opening panes. I was / am tempted to add fans but can always do so later as attic just above so no redecoration or rework would be required... Well aware of fan air feed requirements - one of the reasons I am not too fussed about having one really - an open window usually works better and is quieter!