Acoustic insulation : dry sand between joists ?

10 Aug 2007
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United Kingdom
more on my noisy neighbour project...

I've put down sheets of 100mm thick dense fibre matting between my floor joists - this may keep my flat warm but I am far more interested in achieving acoustic insulation not thermal insulation - all due to noisy lord fauntleroy downstairs and his stereo.

My problem is there is one joist cavity running along the length of my flat that is very inaccessible i.e. I cannot get lay down my soundproofing material into the void.

I read somewhere that sand is sometimes used to achieve acoustic insulation.

For flats like mine where some joist voids are inaccessible ( due to pipes/noggins/stud partitions etc ) is it feasible/sensible to pour dry sand down between the floor joists. This would only be for one joist void ( approx dimensions 100mm high x 300mm wide x 4 metres long ).

Any thoughts welcome.
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I have a thought, but it’s not DIY related and probably not for this board, but here goes.

If it was me I’d treat the problem at source and stop my neighbour disturbing me. There are laws to protect people like you.

First thing is to save neighbourly discord and talk to him about it. Much the best way of dealing with this kind of thing is an amicable discussion.

If all reasonable attempts at being civil fail you should first contact the letting agent if you let, or the management company if not. Your next call should be to the council.
If all reasonable attempts at being civil fail you should first contact the letting agent if you let, or the management company if not. Your next call should be to the council.

Thanks for your support. I did use your approach i.e. council and manage co. earlier this year to resolve a different problem, a leak from the flat above. I was successful so I don't rule out trying the same again with my noisy neighbour. RBKC council have an excellent noise team.

However, it's also true that builders in the 1860's gave no thought to acoustic insulation. They had their hands full fitting hot running water. As a consequence London is stuffed full of noisy Victorian buildings that may need fixing. I place some of the blame for my noise problem on the original construction of my home which I am trying to put right.
Sand has been used in the past for this purpose. It may be a problem for downstairs if they ever renew their ceiling.
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Reynard - 'back in the day' (1970's) we used to convert large period houses in London into flats and apartments; all of this work was governed by 2 local authorities, the Local Council and the Greater London Council (GLC). As you can imagine there were loads of regs, some often contradictory, but Acoustic Insulation was very clear.

Airborne noise and impact noise both need to be treated in different ways. Your issue appears to be airborne up through the ceiling/floor void and should be addressed by increasing the floor mass by filling the void with vermiculite granuals (come in sacks and is very light in weight). Sand would have the same effect but because of it's weight WILL collapse the ceiling onto noisy lord fauntleroy downstairs and his stereo (so do not use sand). Impact noise (footfall) is prevented by installing acoustic quilting over the existing floor and then 'floating' a new floor above.
I agree, do not use sand, too heavy.

The most you can do is stuff insulation between the joists, don't know what this dense fibre stuff is all about though.

Overlaying you floor with boarding of some kind will also help, to seal the gaps. Thin ply or hardboard would help if the floorboards are particularly gappy.

If the sound is structural though then you will have to get the floor up and lay floating on neoprene strips, even this will need to be calculated and the dead weight of the room worked out etc

The vermiculite wouldn't add any mass due to it's light weight.

No easy options whichever way you look at it. :(

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