Rockwool alternatives for internal floors, walls & loft?

[ruggers]

I'm pricing up various internal insulation for a self build and wondering if there's any good cheaper alternatives than the Rockwool brand for use stud walls and intermediate floor to reduce sound or is it the best? Also any good brands of mineral wool for a cold loft floor/upstairs ceiling.

 

Stud walls specified - 75mm Rockwool RWA 45 - 45kg/m3

Intermediate floor specified - 100mm Rockwool flexi - 33Kg/m3

Loft - 400mm no brand specified.

 

The Rockwool flexi seems to be a lot more expensive than RWA45 and the RWA45 is denser so surely better for sound absorption?

[nod]

We mainly use 25 mil acoustic in party walls and ceilings There’s a misconception that packing it full of rockwool is better The insulation is there to stop the sound bouncing round the void 

[ruggers]

So the extra cost of increasing a sound slab from 25mm to 50mm or 50mm to 75mm thick is very minimal in terms of sound absorption?

 

I understand that sound reduction is  bit of a minefield and you can double up on plasterboard, use 15mm soundboard, resilient bars on ceilings etc. but it can get out of hand cost wise for a full build. What I don't want is to be able to hear every noise in a room above or below or through a wall and regret not doing that little bit more but I also don't want to spend £1000's more for very little gain.

 

Areas for the best sound reduction I need are, one bedroom above a main living room and the main bathroom which is between two bedrooms and above a kitchen diner. Also the ground floor bathroom. In my current 1960's house with nothing between the floor, if you have a pish in the upstairs bathroom you can hear it in the kitchen like thunder 😀

[crispy_wafer]

just to chime in,

 

For bathrooms, I've been told to double up the plasterboard.  Got RWA45 50mm as infill for studs.

 

For ceilings I bought some knauf 100mm acoustic.

 

Got a load of res bar, but, a cock up with the full size window height in the lounge means I have about 30mm of frame to play with.

[nod]

1 hour ago, ruggers said:

So the extra cost of increasing a sound slab from 25mm to 50mm or 50mm to 75mm thick is very minimal in terms of sound absorption?

 

I understand that sound reduction is  bit of a minefield and you can double up on plasterboard, use 15mm soundboard, resilient bars on ceilings etc. but it can get out of hand cost wise for a full build. What I don't want is to be able to hear every noise in a room above or below or through a wall and regret not doing that little bit more but I also don't want to spend £1000's more for very little gain.

 

Areas for the best sound reduction I need are, one bedroom above a main living room and the main bathroom which is between two bedrooms and above a kitchen diner. Also the ground floor bathroom. In my current 1960's house with nothing between the floor, if you have a pish in the upstairs bathroom you can hear it in the kitchen like thunder 😀

No need for slab 

ISO roll is fine 

[ruggers]

47 minutes ago, crispy_wafer said:

just to chime in,

 

For bathrooms, I've been told to double up the plasterboard.  Got RWA45 50mm as infill for studs.

 

For ceilings I bought some knauf 100mm acoustic.

 

Got a load of res bar, but, a cock up with the full size window height in the lounge means I have about 30mm of frame to play with.

I've seen a few comments on old posts mentioning doubling up the plasterboards. I wasn't sure if it's worth it for the cost vs difference it would make.

I've used 15mm sound block before and in an old house lined a floor & neighbouring wall with 25mm plank which is just a 25mm thick x 600 x 3000mm plasterboard. I didn't find it too effective.

I've just contacted Knauf about their products this afternoon, they seem much more reasonably priced for the loft & possibly floor void too.

35 minutes ago, nod said:

No need for slab 

ISO roll is fine 

Was the iso roll for the stud walls and intermediate floor?

I've never added slab or iso roll to an intermediate floor from the ground floor, I was lucky enough to drop it in from above and then lay my floor years ago.

 

Is it hard to keep it in place until the plasterboard ceiling goes up? I have a 250mm posi joist void but have heating pipes to run, and then in the kitchen will have down lights sticking up into that space so it's where to position the 100 or 150mm insulation. Top, middle or lower part. 600mm centres.

[SuperJohnG]

I'm using 50mm APR (acoustic partition roll) in all studs after seeing on here not to touch each side. 

 

Soundbloc on all important walls between bathrooms and bedrooms. 

 

On all ceilings from lower floors I'm using Soundbloc 15mm then normal 12.5mm pb minimum 100mm insulation. 

 

On my main lounge which has the master bedroom above I'm using two sheets as above plus mounting the pb on resilient bars plus 100mm APR. 

 

As said I'd rather use more on a specific room and be happy I've done as much (within the bounds of normal) as possible. 

 

Forgot to add I got 100 sheets of 2.7m high soundbloc for 4 quid a sheets. That's why I'm using so much. 

Edited January 6, 2023 by SuperJohnG
Added info

[ruggers]

1 hour ago, SuperJohnG said:

I'm using 50mm APR (acoustic partition roll) in all studs after seeing on here not to touch each side. 

Is APR a specific brand or just a title? Not to touch each side, do you mean in a 100 deep wall ensure the APR only touches one room side wall and the other needs an air gap between the backside of the plasterboard and the APR?

 

1 hour ago, SuperJohnG said:

On my main lounge which has the master bedroom above I'm using two sheets as above plus mounting the pb on resilient bars plus 100mm APR. 

Your going to mount the resilient bars onto a double boarded ceiling then hang a third layer of board off the bars? Some people add green glue or a cheaper equivalent between double boards. Not sure how effective it is.

[SuperJohnG]

1 hour ago, ruggers said:

 

Your going to mount the resilient bars onto a double boarded ceiling then hang a third layer of board off the bars? Some people add green glue or a cheaper equivalent between double boards. Not sure how effective it is.

No just RB then double boarded. 

[ruggers]

I didn't think RB would support the weight of 2 boards hanging from it.

 

When RB is screwed to joists and then you screw the boards to it, is there any movement if you press the ceiling upwards or is everything as solid as board direct onto joists?

[SuperJohnG]

On 07/01/2023 at 17:45, ruggers said:

I didn't think RB would support the weight of 2 boards hanging from it.

 

When RB is screwed to joists and then you screw the boards to it, is there any movement if you press the ceiling upwards or is everything as solid as board direct onto joists?

I've not fitted it yet. It'll definitely support 2 layers its fine in the British gypsum video.