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Author Topic: small floating room, with a light weight concrete floor  (Read 8580 times)

PeterDraaisma

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small floating room, with a light weight concrete floor
« on: October 26, 2010, 04:47:05 pm »

http://recforums.prosoundweb.com/index.php/t/32439/0/ (previous thread)

After all the information and all the reactions on this forum I first decided to stop with the project because of the difficulties and the limitations of the building. But after a visit from the neighbour during a recording session of a cagon I have to go on with the project.

First I spoke with the constructor of the building, he is prepared to check my final design to be shure that the building can handle the weight of the construction. He also confirmed me that it wouldn't’t be a problem to hang the ceiling to the floor of the second-floor. So that’s good news to reduce the weight J.

I will hang the ceiling with, clips like the isohangers, 2 layers of drywall, and a layer of glass-wool between the existing ceiling and the drywall.

The floating floor will be made of regufoam benches/pads. Merford calculated the amount and type of regufoam that has to be used for the weight of the construction.(I also had grate advice from Alara-Lukagro, with kidpads) There should be 1/8m2  of foam under each m2. I was wondering what would be the best way to spread the weight, long small benches or pads, on the net I see both. In this design I go for the benches cause it is easyer to work with.

The benches will be 5cm wide and 3.7 cm height, , with a layer of obs on it, the total height of this will be 3.7 cm + 1.8= 5.5 between the benches there will be a thin layer of +/- 3.5 cm rock-wool/glass-wool. On the obs I will put lewis-board, with 5 cm light concrete(1700 kg/ m3). The floor will be on whole floor, to spread the weight over a  as big possible surface. There will be a gap of 5 cm around the floating floor with a layer of glass-wool.

The wall will be made of metal studs, with 2 layers of drywall and the gap between the existing wall(25 cm concrete) will be stuffed with 14 cm of glass-wool.


The

Static weight   120,45 kg m2
dynamic weight    33,34 kg m2
Total weight   153,79 kg m2

I draw some pictures of the construction in excel, I will scan them tomorrow and Will post them.

I'm looking forward to your reactions, i think that this is the best that can be done within the limitations of the building.

Best regards,

Peter
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #1 on: November 04, 2010, 08:05:16 pm »

It did take a while, but here are the files. I'm looking forward for your advice en comments.

Best regards,

Peter
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #2 on: November 04, 2010, 08:07:18 pm »

And the other file, with my ideas for the best way to spread the weight, i think v3 is the best.

Best regards,

Peter
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Thomas Jouanjean

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Re: small floating room, with a light weight concrete floor
« Reply #3 on: November 05, 2010, 08:17:30 am »

What's the natural frequency of the Regufoam under this load? Is it low enough? (<10hz?)

You likely need to vent the air cavity under the floor more than that. What's the floor self-resonant frequency with the current air gaps?

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Thomas Jouanjean
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #4 on: November 05, 2010, 10:17:32 am »

Hi Thomas,

It is calculated with the regufoam 150, it is in its dynamic range between 0.010 N/mm and 0.015 N/mm, my total weight will be 0,012395154N/mm2 max. There will be 1/8 m2 regufoam at every m2.

The natural frequency of the regufoam, will be about 7hz by the 5cm and 9hz by 3.7 cm thick regufoam.

Do you mean with"You likely need to vent the air cavity under the floor more than that" that the airgap has to be bigger between the existing floor and the floating floor? how be has the airgab to be, I'will isolate it with rockwool

How do you calculate the floor's self resonant frequency?

Thanks,

Best regards,

Peter
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Thomas Jouanjean

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Re: small floating room, with a light weight concrete floor
« Reply #5 on: November 07, 2010, 06:49:34 am »

By venting I mean that you have to make sure that the air trapped under the floor (even if there is rockwool or else - I actually wouldn't recommend you use Rockwool under a thin floor...) will not be influencing or basically nulling the effect of the Regufoam, and therefore you need to "vent it" in a certain way. Like a Helmholtz. So what you have to check is that the compression of air when the floor moves under deflection and during normal use of the room is such that it does not interfere with the Regufoam behaviour. This is what you have to calculate.

So make sure that the air can circulate faster in and out of the space under the floor than it takes for the Regufoam to compress.

Is Martijn your contact @ Merford? Smile
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Thomas Jouanjean
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #6 on: November 07, 2010, 08:04:36 am »

Hi Thomas,

You mean that if the floor floats on the regufoam, it must not lean on the airpression between the benches? So there has to be an airflow circuit under the floor,between the benches, with an opening to let the cavity breath?

So glasswool will be the best underneath the floor?

And I was thinking that I was all most there for the design of the floor:-(

Mark is my contact by Merford

Thanks.

Best regards,

Peter
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Thomas Jouanjean

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Re: small floating room, with a light weight concrete floor
« Reply #7 on: November 08, 2010, 11:46:58 am »

PeterDraaisma wrote on Sun, 07 November 2010 07:04

Hi Thomas,

You mean that if the floor floats on the regufoam, it must not lean on the airpression between the benches? So there has to be an airflow circuit under the floor,between the benches, with an opening to let the cavity breath?


Exactly! and you have to make sure that the air can circulate fast.

PeterDraaisma wrote on Sun, 07 November 2010 07:04

So glasswool will be the best underneath the floor?



Nothing there is best in your case. Hey, saves money too! Very Happy
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Thomas Jouanjean
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #8 on: November 08, 2010, 01:20:31 pm »

Hi Thomas,

Thanks again, I'm learning:-). But were do you let the air go, in the mass -airspring -mass wall construction or in an special hole? Cause my existing walls are one part of mam construction,

I always thought that glass-wool underneath the floating floor had a damping function,so the cavity would not resonate. Why is in my case nothing the best?(for a better air circulation?) Is is this the reason why the self-resonant frequency is so important.

So the 5 cm regufoam would be better than 3,7 cm because it goes lower in natural frequency out 7hz instead of 9hz.

Do you have links where I can learn more about the self-resonant frequency?

best regards,

Peter

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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #9 on: November 22, 2010, 04:06:45 pm »

Hi Thomas,

I made two drawings for the air circulation under the the floor.I'm looking forward for the comments. Which of the two is the best?

I'm still looking how to calculate the self-resonant frequency of the floor.

Best regards,

Peter
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #10 on: November 22, 2010, 04:08:23 pm »

And the other drawing. Smile
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Thomas Jouanjean

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Re: small floating room, with a light weight concrete floor
« Reply #11 on: November 22, 2010, 04:58:08 pm »

I'll have a good look when there is some time. What hypothesis did you base your estimation on?

Re: floor's resonance frequency. It's difficult to calculate and too complex to explain in less than a few pages. I'll also see to estimate it quickly for you, if time allows. Smile

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Thomas Jouanjean
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #12 on: November 22, 2010, 05:39:23 pm »

I did i with reason and common sense ;-):

The benches have to be in the other direction than the lewis board. So there have to be gaps in the benches, otherwise you can't vent. The amount of airflow underneath the floor when it floats isn't big(I presume, I looked at the kippads, when you squeeze them there is little air coming out of the pucks, when I press the sample of regufoam there is also a little air movement.) I also looked at the building thread of the amsterdam mastering and i could not find your vent;-), so i presume i could not be big.

The floor wouldn't move a lot, maybe a few mm, so there can't be a lot of pressure building up underneath the floor.

What do you think of my hypothesis?

best regards,

Peter
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Thomas Jouanjean

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Re: small floating room, with a light weight concrete floor
« Reply #13 on: November 23, 2010, 07:07:59 am »

PeterDraaisma wrote on Mon, 22 November 2010 16:39


The benches have to be in the other direction than the lewis board. So there have to be gaps in the benches, otherwise you can't vent. The amount of airflow underneath the floor when it floats isn't big(I presume, I looked at the kippads, when you squeeze them there is little air coming out of the pucks, when I press the sample of regufoam there is also a little air movement.)


Just to make sure, it's not about the air in the Regufoam, it's about the air around it and trapped under the floor when the floor moves (and it does, especially when light). I would not be surprised if you could have movements of up to 7 or 8 dm
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Thomas Jouanjean
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PeterDraaisma

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Re: small floating room, with a light weight concrete floor
« Reply #14 on: November 23, 2010, 04:57:38 pm »

Thanks again Thomas,

I understand:-), you made it clear for me:-) Mhm, but what would be the best less bigger gaps or more little gaps in the benches, see the drawings.

But is this the reason why you didn't recommend the use of a layer of glaswool/rock wool under the floor?

Best regards,

Peter
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