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Building walls on a floating floor? Channel Strip Plugins
Old 12th September 2011
  #1
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Building walls on a floating floor?

Hi there,

It might seem a simple question but I'm having great difficulty finding the answer...?

With a floating floor construction, would you build the interior walls on top of the floating floor and attach them to the roofing rafters or would you need them to stand-alone and have a 'floating' ceiling too?
Because my thought is that if you attach the new interior wall structures to the rafters surely the sound will travel through the rafters and down the wall... defeating the whole point of having a floating floor in there?

Cheers, Adam.
Old 12th September 2011
  #2
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Quote:
Originally Posted by thecurtain View Post
Hi there,

It might seem a simple question but I'm having great difficulty finding the answer...?

With a floating floor construction, would you build the interior walls on top of the floating floor and attach them to the roofing rafters or would you need them to stand-alone and have a 'floating' ceiling too?
Because my thought is that if you attach the new interior wall structures to the rafters surely the sound will travel through the rafters and down the wall... defeating the whole point of having a floating floor in there?
It depends on how much isolation you need and where the sound sources are. In general terms, you are coreect int hat the ceiling needs to be "floating" for a full envelope around the space.

Andre
Old 13th September 2011
  #3
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thanks Andre, the sound will be coming from with the room and I'm trying to decrease the volume on the ground below (as this will be a lounge) ... do you think there will be much difference between attaching the walls to the rafters and building a 'floating roof' with regards to low/mid range freq's coming through to the lounge?
thanks again
Old 13th September 2011
  #4
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Quote:
Originally Posted by thecurtain View Post
thanks Andre, the sound will be coming from with the room and I'm trying to decrease the volume on the ground below (as this will be a lounge) ... do you think there will be much difference between attaching the walls to the rafters and building a 'floating roof' with regards to low/mid range freq's coming through to the lounge?
thanks again
you have not provided enough information. Aside from what the flanking paths are, you write rafters. Does this mean a roof? There is no rain on the roof? There are no other neighbours to be concerned with?

That still leaves the questions of flanking paths.

Andre
Old 13th September 2011
  #5
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To float a floor when it is supporting the weight of the walls is a more complicated acoustic engineering exercise than floating the walls and the floor separately. To build a "box within a box" you would normally have a resiliently suspended ("floated") ceiling as well. This is for maximum sound insulation. Which may or may not be required in your case. At the very least, the walls should have an acoustic detail to restrain the top of the walls so that they are not rigidly fixed to the rafters.
Old 13th September 2011
  #6
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Thanks for the replys guys...

When I write rafters I mean- wooden beams the the roof is held up by, I'm in the top room on a three storey building you see...
There's no rain on the roof no as it's slanted with guttering and there are no direct neighbours no... I just want to reduce the db to as low as possible in the lounge (which is on the floor directly below)

With regards to flanking paths, I hope to almost eradicate these with the floating floor and suspending ceiling techniques, however I understand I will still be facing some problems with regards to fitting my sockets/lights into the "box within a box"?

Sebg- you mention floating the walls separately, how would you recommend doing this? The same way I've done the floor? With neoprene 'feet' on the bottom? How would they stand if you can't screw them to the rafters...would you screw them to the floating floor?

thanks again for the replys, it's really appreciated
Old 14th September 2011
  #7
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thecurtain,

this has come up here so many times... I'm surprised that people are still taking the trouble to explain.

Your "true" floating floor system has to be very rigid and heavy. It should have a resonant frequency of under about 10 Hz in order to provide you with the isolation you desire. This requires serious mass, and many subfloors cannot support this much additional weight. Unless you have 8" or more of concrete subfloor, you are likely to be in this boat.

a practical compromise can be found here. The walls will however have to be built outside this floor, as the floor will not be strong/rigid enough to support the walls and ceiling. You will have to use acoustic hangers to isolate your inner ceiling from your existing ceiling.
Old 19th September 2011
  #8
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Quote:
Originally Posted by audiothings View Post
a practical compromise can be found here.
Not really. This may be one solution for impact noise, but it will actually reduce the sound transmission loss of the floor partition at it's resonant frequency.. which is probably above 100Hz. I do not recommend this type of floor unless you need the thermal insulation and you are on a ground floor slab.

-- and then you don't need a floating floor anyway.

Cheers,
John
Old 28th October 2011
  #9
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Quote:
Not really. This may be one solution for impact noise, but it will actually reduce the sound transmission loss of the floor partition at it's resonant frequency.. which is probably above 100Hz. I do not recommend this type of floor unless you need the thermal insulation and you are on a ground floor slab.
Sorry, just saw this six weeks after John's post...

John, coincidentally, I made the same recommendation (as you) to someone, earlier today. I suppose you are talking about the MAM resonance of the two floors. If you look at that link again, you'll see that the frame is 50 mm deep and resting on a bed of 100 mm rockwool, and that 50 mm frame is stuffed with 200 mm loft insulation. I don't think the addition of the frame is making it a resonant chamber, as it is resting on rockwool and not a solid mass, and also it is very highly damped, FWIW. Do we really have an MAM system here or are you talking about some other resonance?
Old 28th October 2011
  #10
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by virtue of having the frame, there is an air chamber there (albeit filled with insulation) which will likely cause unwanted resonances. now if the frame were filled with sand, it would be less of a concern from an acoustics standpoint but then the weight could be a problem.
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