Pugging requirements

I'm interested in using pugging to remedy the noise pollution that I get from the flat downstairs. As this involves attaching MDF to the joists and pouring on a lot of sand (about 80kg/m2) I've read that some joists are unable to take the extra weight. Does anyone know if there is a rule of thumb that can be applied to see if the joists can take the extra weight or would I have to rely on calling in a local builder to do the calculation?
Thanks in advance, Mike
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Chomski wrote:

Some years back I had to do some calculations for a lintel. Amongst other things, it had to support a floor and I recall when looking up the imposed load for a floor, it being about 2.5 people per square metre. Your sand will be about half this. So if your floor is to a modern design and in good condition and not had extra holes in the joists for extra wiring etc etc. Then you might be OK. If your floor bounces when walked on etc then you should either re-inforce it or get advice from a structual engineeer.
Bob
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Chomski wrote:

I wouldn't trust a builder - you need a structural engineer.
Steve
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wrote:

That sounds like a lot of weight to me, but I can't answer the question.
Would it not be possible to use something like polystyrene chips rather than sand?
PoP
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Mass. Nowt else. Mass. And decoupled mass: mass wot can move a little bit to absorb the sound energy and turn it into heat, rather than a rigid mass which moves as one lump and makes the air on the other side vibrate again just like the vibrations on the noise-producing side.
So the theory behind sand is sound; as is the idea of heavy lumpen (multiple sheets of plasterboard with rubber sandwiched inbetween, and maybe a sheet of steel or depleted uranium ;-) as part of the sandwich), all mounted on stiffish rubber blocks, and extravagant care applied to eliminating air gaps. That's the sort of treatment needed to create viable isolation for recording/crank-up-the-volume-on-the-bass-guitar-amp-to-11 builds; and its cost and awkwardness account for how rarely it's done (and the growing popularity of the prebuilt but claustraphobic "room-within-a-room" steel prefabs, as I've seen advertised in the Studiospares catalogue and had my hearing tested in at a hospital audiology facility).
From which you might, correctly, conclude that none of: polystyrene chips, bits of rockwool, "acoustic" tiles, eggboxes, or hessian will do anything to limit transmission of lower frequencies. Surface treatments like tiles and eggboxes will affect the direct reflection of higher freqs, granted...
As to whether your joists will be up to it - they'll probably support a fair bit of weight if the room is not too big and you have a reasonably decent building, as both Building Regs and builders' rules-of-thumb of the "depth of joist in inches = span in feet + 2" form are effectively limited by deflection, i.e. not wanting the ceiling below to visibly sag, rather than absolute strength. But you'd need proper calculation to be sure, and even if your floor would take the weight you'd still be subject to structure-borne propagation of those pesky low frequencies...
Stefek
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Styrofoam chips will reduce higher frequencies but not lower ones. To do that, you have to add mass, one way or another.

.andy
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PoP wrote:

Yes, but it wouldnt stop sound worth a damn.

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2 tonnes of sand in a small to medium room eh, I dont think I would. What else has been done to address the sound?
Regards, NT
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On 12 Jan 2004 13:54:48 -0800, snipped-for-privacy@meeow.co.uk (N. Thornton) wrote:

Imagine having to lug that lot up the stairs!
Plus sand packaging/transportation tends to leave some residue as you move it around - so presumably by the time this job is done the stairway (or lift?) would be covered in sand.
PoP
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Mass stops lower frequencies. But this may be too heavy for your floors.
I would look into:
1. Installing a floating floor. Usually with rubber on the joists to support the floor. The floor "must not" touch the sides or skirting boards, to reduce flanking sounds (sounds that travel up and down walls ).
2. You can install some mass. Fit over the downstairs plasterboard some HDF between the joists (tight fitting). Do not allow it to touch the walls. Best run a bead of silicon at where the MDF touches the joists.
3. Above this install some mineral wool. Use a 25kg/m3 high density mineral wool roll or rigid batt that fits properly, filling the depth of the cavity without compression. Dedicated acoustic felts cost and arm and a leg and yet don't perform much better than good mineral wools.
The best way is to fit MDF between the joists (secured) and either 1" or 2" of sand over this. But a structural engineer would have to do the calcs for you. I have seen some floors reinforced by bolting new joist periodically across the floor to the existing joists.
The way I itemised above is about the best without too much expense and the floor not caving in. Whichever way you go, installing a floating floor should be done, as you are ripping up the floor anyhow.
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