50mm metal stud wall too thin to separate bedrooms?

jamie765 · 22 Jun 2021

Am building a stud wall and very limited for thickness. Planning to use metal studs as its easier to construct. It's a wall separating two bedrooms so need it to be acoustically sound. I will be fixing acoustic plasterboard to either side and fitting 50mm acoustic wool in between.

Would 50mm metal studs be OK to use for this wall? Or should I really be going for 70mm metal studs with 75mm acoustic wool packed in between?

Deluks · 22 Jun 2021

What you gonna do with all that extra 20mm?

Unless you've got limited space to get the bed in, the thicker one is better all round.

jamie765 · 22 Jun 2021

Deluks said:
What you gonna do with all that extra 20mm?

Unless you've got limited space to get the bed in, the thicker one is better all round.

If I went with the 70mm metal studs, would 50mm acoustic wool be better than slightly packed 75mm thick acoustic wool?

I've read loosely packed acoustic wool is much better than tightly packed as loose wool absorbs sound better... but wondering whether that would be the case in this scenario, where its 50mm loose vs 75mm with just 5mm of squashing

Deluks · 22 Jun 2021

The squashing is fine, the sound reduction difference will be negligible either way, but I'd fill the void completely, and use 15mm acoustic board on one side, and 12.5mm on the other.

Tigercubrider · 22 Jun 2021

you WILL hear everything

jeds · 22 Jun 2021

To comply with Part E; Minimum metal stud is 45mm with 12.5mm dbcheck board each side (minimum density of 10kg/m³) and 25mm acoustic grade mineral wool.

Stuffing the void with mineral is not a good idea. A thinner mineral with a degree of void separation would give a better result.

jamie765 · 23 Jun 2021

Tigercubrider said:
you WILL hear everything

Why do you say that, if this spec complies with building regs even at the 50mm wool with 50mm studs option?

jamie765 · 23 Jun 2021

jeds said:
To comply with Part E; Minimum metal stud is 45mm with 12.5mm dbcheck board each side (minimum density of 10kg/m³) and 25mm acoustic grade mineral wool.

Stuffing the void with mineral is not a good idea. A thinner mineral with a degree of void separation would give a better result.

Interesting thanks, seems there are varied opinions here on which is better out of 70mm studs with 50mm wool + gap.... vs 75mm wool

Either way seems like 70mm studs is still the better option vs 50mm studs (whether I use 50mm wool or 75mm wool) so at least I've got that decided!

jeds · 23 Jun 2021

70 would always be better than 45, acoustically. Good sound attenuation is a combination of high and low density materials, separation and voids. If I recall correctly the optimum void (barrier to barrier) is 200mm. Acoustic sealed windows in schools usually have 200mm gaps between panes of glass.

An interesting fact; low density materials attenuate high frequency sounds - where high density materials attenuate low frequency sounds. So you need both types in an acoustic system.
Another one; there's an old saying in sound school; 10% gaps allows 90% sound to pass through. So seal, seal, seal.

SFK · 23 Jun 2021

Silly question - with 50mm metal studs can you in-step/stagger them (to make say 60mm void width) so sound vibration does not go into plasterboard, through metal and into pasterboard on other side?
This method seperates the two plasterboard walls from each other.

Done tihs with wood studding, but noted it costs more as needs double the vertical studding. And not sure if can be done with metal studding as never used:

Staggered Stud to reduce noise transmission

https://auralex.com/blog/how-can-you-soundproof-your-office-effectively/

jeds · 23 Jun 2021

Not really, Metal stud sits in a channel top and bottom so you wouldn't get the in-out staggered effect. You'd need to build two separate walls close together.

Tigercubrider · 23 Jun 2021

jamie765 said:
Why do you say that, if this spec complies with building regs even at the 50mm wool with 50mm studs option?

Because the building regs are quite a low mark to reach.

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50mm metal stud wall too thin to separate bedrooms?

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