Furrings for sound insulation?

[ProDave]

I have not come across these before.  but the house I am wiring at the moment is using them.

 

It appears to be a thin steel "top hat" section strip. You screw it to the underside of the joists (screwing through the two sides of the "brim" and then the plasterboard screws into the flat part.

 

It's supposed to be a sound proofing measure and this apparently obviated  the need for any actual acoustic insulation.

 

Anyone used these? does it really work? I am skeptical myself as I would have thought the surface of the plasterboard would transmit sound just as well and can't think transmission via the joists (posi joists in this case) would contribute much to sound transmission.
 

[tonyshouse]

Yes, you still need air tightness, rockwool batts inbetween, double boards at least one side, rubber behind the metal resilient bars too.

[ProDave]

This is for ceiling sound proofing. so are you saying as well as the furrings, you need a rubber strip AND 2 layers of plasterboard AND insulation batts?  If so I won't bother. Mine has been specced (and approved by BC) as one layer of plasterboard direct to joists and 100mm insulation.  I was just looking if this was an option to avoid fitting insulation.
 

[daiking]

1 hour ago, ProDave said:

Mine has been specced (and approved by BC) as one layer of plasterboard direct to joists and 100mm insulation. 
 

 

I thought this was one area where the building regs were not worth much. Isn't the insulation requirement just something with a min density of 10kg/m3? So basically loft roll would do to meet the requirement but not actually provide much sound insulation. 

 

What you're going for barely sounds like a belt, let alone braces.

[ProDave]

Personally, I have never had a problem with sound insulation between upstairs and downstairs. I don't have a "complaint" with just plasterboard direct to the joists, floorboard on top and nothing in between. So this is one aspect of the regs I find is "solving" a problem that I do not have.

 

My spec says 100mm and that is what I will fit, though I see it as an unecessary expense and it will be in the way if I later decide to add extra cables for anything.  I was merely asking as what I understood was being proposed in this new build I am wiring is just these furrrings and nothing else extra.
 

[Construction Channel]

unless they put a sound deadening gap between the p,board and the joist like rubber it sounds like snake oil to me, I just can't see it working, why not just put the rubber on the joist? whatever they do the sound can still get through the screw.......

 

i also have never had an issue with noise between floors. which direction is it that people have a problem with? party below while trying to sleep? or beds creaking when trying to watch a film?

 

on the insulation though anything will help if it fills the "echoing" space between the ceiling and the floor above. even crunched up newspaper would help decrease the transfer of sound.

 

personally i am just going for carpet upstairs.

[daiking]

You 2 sound just like typical tradesmen

 

I understood that sound resilient bars were a de facto sound insulation technique but like most things require to be correctly installed to truly be effective. 

 

 

[jack]

It's not voodoo. It's an extremely common part of sound proofing but generally it's used in conjunction with other measures like insulation, green goo and multiple layers of board. 

[Barney12]

14 minutes ago, Construction Channel said:

 

i also have never had an issue with noise between floors. which direction is it that people have a problem with? party below while trying to sleep? or beds creaking when trying to watch a film?

 

I agree. Is this really a requirement in current regs to add sound proofing between floors in a single dwelling?

The only time I can see it as possibly being a real issue is a WC directly above a commonly inhabited room. No one really wants to hear the tinkle and/or plops of their guests  

[ProDave]

But my point is BC have approved nothing more than 100mm of insulation, so why would I bother with all sorts of extra bits of fiddly metalwork?  If the furrings on their own were a "solution" then I might have considered that as it would leave the void clear so future cables might be possible, but if it's furrings and insulation then why bother.

 

I am not a "typical tradesman" it is just in this case I don't have a problem, so I am being forced to "solve" something that is not a problem to me and just looking at what I thought might have been an option.
 

[Construction Channel]

22 minutes ago, jack said:

It's not voodoo. It's an extremely common part of sound proofing but generally it's used in conjunction with other measures like insulation, green goo and multiple layers of board. 

ahhh, but how much do the firing pieces actually add? 

 

without the other bits to make them work e.g the green goo why would a formed metal spacer make any difference?

 

has anyone got a picture of this set up?

[Construction Channel]

10 minutes ago, Barney12 said:

The only time I can see it as possibly being a real issue is a WC directly above a commonly inhabited room. No one really wants to hear the tinkle and/or plops of their guests  

 

good point, hadn't thought of that one

[Declan52]

When you have kids you need to be able to hear them when they are upstairs. As the moment the noise stops you just know some ones up to no good.

[ADLIan]

The resilient bars are often used as part of the acoustic solution in separating floors i.e between dwellings/flats. Also often used if higher acoustic performance required.

 

In partition floors within a dwelling the 100mm mineral wool quilt is the option to comply with Regs.

 

Ian

[jack]

11 hours ago, Construction Channel said:

has anyone got a picture of this set up?

 

Here're a few: http://bit.ly/2cPUaNw

 

The reason you need all the other stuff is that different elements are better at different types of noise and different frequency ranges.  I wish we'd spent more time on this - I'm surprised, for example, how much noise from our TV room leaks into the bedroom above it (which thankfully is only a spare room).

[TerryE]

IMO, this is a case of the regs being OTT and way out of line with 95% of the current build stock.  OK, I think that most of us would see the sense in having good acoustic insulation between attached dwellings, but why have high levels of acoustic separation as a requirement within a dwelling.  Our current farmhouse has its original 300 year-old old beams and elm floor boards.  We replaced the plaster and lathe between the beams by battening and plasterboard, but when you are sitting in our living room, you can hear any guests in the bedroom above fart (let alone other activities).

 

We've got PosiJoists and 50mm Rockwool plus an extra layer around the MVHR ducting in our new build which I think is a sensible compromise. 

Edited September 15, 2016 by TerryE

[Oz07]

De Ja Vu, The regs state the level of sound which must not pass thru, not how you achieve it.

 

Posi joists comply on their own in England, without need for wool in most cases. I'm all for 50mm of wool as above as this fits neatly between top/bottom chords and out the way of services. 42db from memory

[Alex C]

The metal resilient bar is for impact sound such as people walking upstairs wheras rockwool type products are for airborne sound such as talking or tv. To get the best sound insulation you really need something to address both types of sound.  To be honest the top hat section profile you describe sounds more like a standard suspended ceiling product rather than a resilient bar, which is normally a z shape with the top of the z screwed to the joists and the bottom of it screwed to the plasterboard.

 

just seen the link above. the top hat sections rely on being mounted on a rubber bushing for separation.

Edited September 15, 2016 by Alex C

[Construction Channel]

21 minutes ago, Alex C said:

 

just seen the link above. the top hat sections rely on being mounted on a rubber bushing for separation.

 

That makes sense. Tbh i was quite impressed with the picture that had little suspension struts. 

 

metal hard against the joists just didn't make sense to me. 

[PeterW]

I also thought they ran at 90 degrees to the joists as that further reduced the contact point ...??

[jack]

5 minutes ago, PeterW said:

I also thought they ran at 90 degrees to the joists as that further reduced the contact point ...??

 

Yep.  It's about decoupling: less surface area = less energy transfer.  Probably some minor amount of energy absorbed in the bar itself (which will be even less in the "top hat" style), but decoupling is the major factor at work here.

[Alex C]

I have been quoted £6 square meter supply and fit by a tacker so pretty good value.

[ADLIan]

@TerryE - I think you've answered your own question as to why acoustic insulation is required in floors (& walls) within dwellings!

 

Part E was improved considerably back in 2003/4 as a direct result of public concerns about the (poor) qualiity of acoustic insulation both between and within dwellings.

 

Ian

[jack]

I personally think it's hugely important.  

 

We in theory have slightly better than building regs levels of insulation (although I do have my doubts about how some of it was installed when I wasn't present) and I'm not at all happy with the levels of sounds insulation that's resulted.  

 

If doing this again, I'd up the amount of insulation, use resilient bars everywhere, and ensure that all the installation and detailing was perfect.  

[ADLIan]

Yep. Acoustic performance, same as thermal, depends critically upon detailing and workmanship. The smallest of gaps or imperfections in the system will allow sound through and degrade the performance of the floor or wall.