Sound insulation

[Thedreamer]

If my attic trusses are 200mm deep, how far should I fill these with sound insulation?

 

The Knauf website suggests that the 100mm spares loft roll that I have will not have sufficient acoustic properties but would two 100mm layers not do the job?

[nod]

You would be better using acoustic slab 100 mil would be far more effective than full fill loft insulation 

[Moonshine]

What acoustic properties are you looking to achieve?

What is the noise you are trying to insulate against?

You will also need to consider ventilation requirements under the roof layer and U values, as acoustic / porous insulation doesn't perform as well thermally as PIR board, therefore you will need to add thicker insulation

Edited July 18, 2019 by Moonshine

[ADLIan]

Assume this is the floor to the attic rooms and above rooms below. Acoustic insulation required under Building Regs normally 100mm of mineral wool with min density of 10 kg/m³. Loft insulation is normally less than this so does not comply - in reality I greatly doubt there would be any difference in overall acoustic performance if the density is a little low. Using 200mm rather than 100mm would have little effect - case of diminishing returns. You would have to convince Building Control that 200mm offsets the low density or use 100mm of the correct acoustic product.

[joe90]

I am disappointed with the sound transference between floors in my new build, 100mm sound insulation between the I beams is not enough in my opinion, I wish I had doubled the plasterboard or soundblock plasterboard or rails to hang the plasterboard on. There are no air gaps through the flooring upstairs so it is ceiling/insulation that is lacking.

Edited July 18, 2019 by joe90

[ADLIan]

Adding more acoustic insulation will achieve little. Next improvement is to add mass with 2 or more layers of plasterboard and then to decouple the plasterboard from the joists using resilient bars

[Bitpipe]

I visited the house of one of the original e-build era MBC builders in Oxford. He spent a fortune on resilient bars, heavy rubber matting, sound block board - the works.

 

It made some difference but did not eliminate the issue.

 

We have soundblock (blue) pb on basement ceiling and ground floor ceilings, plus on bathroom walls that meet halls etc. Makes some difference I'm sure but you still hear some noise from below.

 

We have wooden floors on first floor so you *really* hear that downstairs. 

[nod]

3 hours ago, joe90 said:

I am disappointed with the sound transference between floors in my new build, 100mm sound insulation between the I beams is not enough in my opinion, I wish I had doubled the plasterboard or soundblock plasterboard or rails to hang the plasterboard on. There are no air gaps through the flooring upstairs so it is ceiling/insulation that is lacking.

I use a lot of res bar 

But if you can spare 50 mil off your ceiling height and MF ceiling hung from the joists Is Far better than res bar  

[Moonshine]

48 minutes ago, nod said:

I use a lot of res bar 

But if you can spare 50 mil off your ceiling height and MF ceiling hung from the joists Is Far better than res bar  

 

but fit the MF ceiling to joists with a GAH1 type acoustic hanger.

[nod]

Last I installed a floor using gypsum Metset in the place of the joists It was like walking on a concrete floor Ultra straight but solid as a rock Hardly any sound transfer

But comes at a cost   

[Thedreamer]

Thanks for the replies.

 

The upstairs is a room in the roof design. We have been limited by ridge height because are building in a special scenic area. Therefore can't lose any height from additional plasterboard layers.

 

The house is split into three sections. At either end it is attic trusses where I have 200mm depth for the joists. I think from reading the above I'll scrap the loft insulation idea, so is it worth fitting 2 x  100mm acoustic insulation, just 100mm acoustic insulation or even put in 100mm acoustic insulation and the 100mm loft insulation underneath as well?

 

The middle section is partly vaulted and open plan so less worried here. 

 

Upstairs I plan to fit carpet and a good underlay. Chipboard has already gone down. 

 

For the resilient bars, do these consist of two types one for floors/ceilings and second for walls? 

 

 

 

[nod]

Two 15 mil sound boards will make a difference 

The res bar fits to the underside the floor 

one type for walls and ceilings

Just pin one edge I always work left to right to keep them running the same way 600 centres