Noise reduction - MF, Resillient bar or just fix to posi joists

[Simon R]

We're going round in circles trying to decide how best to finish our floors to get an acceptable level of sound proofing. Our bedrooms are on the ground floor separated  from a hall and stairs by 4x1 stud walls in which we'll put 100mm RW45  and double up on the plaster board on the hall side. The stair  is open and connects with the first floor which is open plan. So no sound deadening between the living area and the hall area. The doors from the hall to the bedrooms are good heavy and well sealed. We would like to be able to have the bedrooms quiet enough to sleep in even if someone is watching TV or playing music upstairs. I don't think we will be able to completely deaden foot fall.

 

The floor is 300mm posi joists on 400mm centres, with 22mm caberdeck and we are putting 100mm Rockwool Flexi Slab between the joists (RW45 is only available in 600mm).  The floor edges will be air sealed to reduce airborne sound using Siga tape or the 3M equivalent.

 

We are adding the two layers of 12.5 plasterboard, our choices for fixing this are;

1. Directly to the posi joists - no decoupling.
2. Use resilient bars
3. Use MF with GAH1 hangers.

Trying to find informations on what level of sound reduction each option offers is proving fraught. Our gut feel is that the MF solution with GAH1 hangers has the best chance of delivering the sound reduction we require.

 

Not entirely happy proceeding on gut feel with no data!

 

[nod]

An independent MF ceiling will always be your best option 

Look back at a previous post I added Recommending a simple fast Gypliner system 

Your next best is res bar 

Independent ceiling  wil take about an hour for a 25m2 ceiling 

Red Bout 20 mins

[Alex C]

You also need to look at floor to wall/skirting details in the room above as a lot of sound is transferred from floor down the wall. Try and track down some robust details as there are lots of examples of how to deal with this. 

[Moonshine]

1 hour ago, Simon R said:

We are adding the two layers of 12.5 plasterboard, our choices for fixing this are;

1. Directly to the posi joists - no decoupling.
2. Use resilient bars
3. Use MF with GAH1 hangers.

 

as below (note that the Rw values are in the lab, real world performance D_nT,w will be below these)

 

1. tbc (but less than 2 and 3, this floor would be about R_w 42 dB without insulation in the cavity)
2. Circa R_w 52 dB (BG system ref C206009 is R_w 54 with two layersof 15mm SoundBloc)
3. Circa R_w 63 dB (BG system ref C106026 https://www.gyproc.ie/sites/default/files/C106013.pdf)

Edited December 4, 2019 by Moonshine

[Moonshine]

1 hour ago, Simon R said:

I don't think we will be able to completely deaden foot fall.

 

if you want to, consider using a product like Screedboard 28 or JCW acoustic deck above the caberdeck to reduce foot fall.

 

Are you most concerned about foot fall or airborne noise?

Edited December 4, 2019 by Moonshine

[Simon R]

8 hours ago, Moonshine said:

Circa R_w 63 dB

definitely MF then 63 DB is a big difference!

thanks for the tip about Screenboard 28, I'll take a look at that. Foot fall is not my main concern so it may not be worth considering a floor covering.

thanks

Simon

[Moonshine]

58 minutes ago, Simon R said:

definitely MF then 63 DB is a big difference!

 

It's doesn't work like I think you think it does. That quoted 63 dB isn't the sound reduction you get from one room to another.

One because is a weighted value of measurements at third octaves between 100Hz to 3.15KHz, and a couple of other corrections. Two became it's a lab results with different corrections to the real world, also it's been built absolutely correctly, and has no flanking paths.

However it's is useful to compare between constructions.

[Simon R]

35 minutes ago, Moonshine said:

That quoted 63 dB isn't the sound reduction you get from one room to another.

So the test covers the speech spectrum, which I guess is a reasonable approach. I'm only going to do this once so I'll go the MF route, combined with attention to skirting and board sealing detail.

Thank you for your help.

[Simon R]

11 hours ago, Alex C said:

You also need to look at floor to wall/skirting details in the room above as a lot of sound is transferred from floor down the wall

It's an ICF build so we should get next to nothing transmitted through the walls. I'm going to seal the floor to the ICF using 3m 8067 tape to try and prevent  transfer.