Resilience bars or double skin pb

[eandg]

Hi, 

 

Sheeters are due to put ground floor ceilings in next week. I have 15mm PB on site and was about to hit the button on ordering resilience bars when I realised they will work out more expensive for materials than a second skin, but will likely be a fair bit cheaper on labour. Any thoughts on what the best option would be?

[Alan Ambrose]

Double PB is a bit hard work for typical PB back boxes as they're only designed for one layer. You can make them work if you really want.

[saveasteading]

Resilient bars work differently to the second layer of pb. Lab results can be very different to real life.

I think bars are better in real life because of breaking the continuity.

 

But it is essential that they are fitted properly to maximise their flexibility.

Don't assume that the fixer knows this, understand this or accepts this.

"Just an extra screw" through the wrong part, and the function is compromised. 

[eandg]

Thanks - think I'd be doing the resi bars at the weekend in advance of them. So as long as guidance is followed, 36mm screws into joists then leave them with only 25mms for the install all should be good?

[saveasteading]

30 minutes ago, eandg said:

36mm screws into joists

Using the appropriate flange only. 

Good thinking re the diy.

I think I would still be explaining the principles and watching them though.

 

Explain it for the few seconds until the eyes glaze over.

I'm not being rude..some people do theory and others don't. 

[Mike]

Resilient bars reduce impact sound. Extra plasterboard reduces airborne sound. Which type of sound transmission concerns you the most?

[eandg]

Just now, Mike said:

Resilient bars reduce impact sound. Extra plasterboard reduces airborne sound. Which type of sound transmission concerns you the most?

Both - three kids bedrooms above. Build up is LVT, underlay, 262mm joist with 100m flexi slab, (resilient bars/pb), pb. 

[Mike]

35 minutes ago, eandg said:

Both - three kids bedrooms above.

Then it may be worth going for the resilient bars and the extra plasterboard...

[saveasteading]

Not necessarily accurate due to source, but from a quick Google 

And it is not as simple as this anyway

 

Resilient bar

 

Airborne Improvement:19 dB

 Impact Improvement:15 dB

 

I just found in projects where noise between rooms was important, that resilient bars seemed to work well for airborne and impact sound, perhaps better than expected. 

I think it is the difference between a wall in a  lab and in a real building.

 

Whatever you do, the weakness is noise through the sole plate or floor, or through the side walls....even electric sockets.

 

Either double board or RB will give a decent performance. 

[SteamyTea]

Do resilience bars work like a spring/damper combination.

Simple harmonic motion.

 

[Dan F]

Another thing to consider is that you don't necessarily have to use resilient bars on both sides of the wall, you can get a lot of benefit from using them just on one side.  We used double PB on both sides +resiliant bar on just one side in critical locations.

 

Look at the British Gysum white book if you want to see decimal reduction numbers for the different options.

 

https://www.gyproc.ie/sites/default/files/Non-loadbearing timber stud.pdf

Edited June 1, 2023 by Dan F
added link

[saveasteading]

59 minutes ago, SteamyTea said:

Do resilient bars work like a spring/damper combination.

Resilient (sic) bars do so indeed. 

 

I have observed them in action from the inside.

 

When you see them first fixed it seems obvious that they are a wobbly, springy fit. The plasterboard flange is the wobbliest bit.

Then plasterboard goes on and it seems to be a robust structure again. But it works as the other flange is now the wobbly one...it just twists very slightly under load, and presumably under a sound wave behaves erratically and kills it.

 

If you bang on the junction of bar to stud, then there is a direct connection, but that will be unusual and minor.

[Iceverge]

4 hours ago, eandg said:

262mm joist

 

Solid Joists? 

 

If so i would expect resilient bars are a must. Also you get a nice 16mm service cavity for your wires rather than drilling. 

[eandg]

Just now, Iceverge said:

 

Solid Joists? 

 

If so i would expect resilient bars are a must. Also you get a nice 16mm service cavity for your wires rather than drilling. 

 

I joists - electrics already ran. Sticking slab insulation and any plasterboard prep on this weekend. 

[eandg]

On 01/06/2023 at 13:24, saveasteading said:

Using the appropriate flange only. 

Good thinking re the diy.

I think I would still be explaining the principles and watching them though.

 

Explain it for the few seconds until the eyes glaze over.

I'm not being rude..some people do theory and others don't. 

Was a wee delay in getting the ceiling sheets up, but was on site with the boys putting the sheets up today. They're good joiners and put resilience bars on most of the jobs they do (mix of commercial and residential). 

 

"So it's 25mm screws you're using?" 

"No, we just use 32s"

"But you're 16mm for your resilience bars and 15mm sheets, so you'll be going into the joist"

"It's only a mil and you'll hardly get any biting across the full place"

"Are you not kinda missing the point of resilience bars?"

 

Lunch called early while I ran for some collated 25s. And just the latest in a long line of how decent trades would miss the important details if left to their own devices.