experimental sound proofing

[JohnAnderson]

Although I have heard many recommend the use of sand as a sound proofing medium I am planning to apply it in a slightly unorthodox and potentially risky manner.

I am trying to sound proof a floor/ceiling in a cost effective way. One part of the solution is to fill the space between the joists from above with sand. A layer any thicker than an inch or so is likely to pop the ceiling out. So, I was planning to partially drive some four inch nails horizontally into the joists just above the existing plaster and lath ceiling (approx 3/4 inch). I will then in-fill the joist space with a dry mix of sand and cement so that the protruding nails are covered in the hope that these will lock the eventual concrete slabs onto the joists so that any additional loading in the joist space will be taken on the joists rather than than the underlying ceiling. I realise I could inset supporting trays etc. but thought this might repesent a quick and easy method for adding sound absorbing weight to the floor.

Any comments much appreciated.

Cheers,

John

 

[mikric]

Dont do it ! How about rockwool or an acoustic underlay etc. Why do you need to do this ?

 

[mattysupra]

someone is trying to pull our legs here me thinks!

 

[JohnAnderson]

Dont do it ! How about rockwool or an acoustic underlay etc. Why do you need to do this ?

Hi Mikric,

Thanks for getting back. I just thought this was a very cheap way of adding mass to the floor/ceiling and to build a very rigid overall structure. I will probably use a layer of 100mm high density rock wool over the cast slabs (75mm). I will then float a chipboard floor on acoustic underlay laid on 19mm plywood screwed onto the joists.

Ideally I would also replace the ceiling with one hung on resilient bars but the current ceiling was only recently over boarded and I'm reluctant to either lose any extra height or rip the whole thing down to replace it.

I thought the idea of locking the mass to the joists was reasonably innovative, are there any structural reasons why this might be dangerous? I'm not a structural engineer (obviously) but am fairly sure the existing joist work is quite capable of with standing this mass, approx 1.25 tonnes (and some).

 

[mikric]

I thought the idea of locking the mass to the joists was reasonably innovative, are there any structural reasons why this might be dangerous?
Yes lots of reasons !
Why do you need to add sound proofing to this floor ?

 

[JohnAnderson]

I thought the idea of locking the mass to the joists was reasonably innovative, are there any structural reasons why this might be dangerous?
Yes lots of reasons !
Why do you need to add sound proofing to this floor ?

Hi mikric,

The usual reason, noisy neighbours, we are just going through the process of soundproofing the entire flat and I happen to have access to the floor space above this room. I know the method sounds a bit stupid but I don't see why adding a mass equivalent to roughly 4 sheets of 19mm plaster board should necessarily be structurally risky and this should produce a very effective barrier to airbourne sound without having to cut, fit and seal trays (the standard method)

John

 

[Reynardine]

I will probably use a layer of 100mm high density rock wool. I will then float a chipboard floor on acoustic underlay laid on 19mm plywood screwed onto the joists.

I'm currently fitting this arrangement with slight differences. For my sub floor I'm using 18mm marine ply sheets, 8 foot by 4 foot, instead of chipboard. Between the joists I'm packing 200mm high slabs of dense fibre matting. This stuff is high density 140kg/m3 not rockwool and is available from knauf insulation ( no connection ). I'm also sticking 5mm x 1 metre rubber joist strips to the tops of my joists, immediately under the sub floor. I'll be putting down further noiseproofing on top of the sub floor. I was tempted to put sand down but my joist spans at 5metres are already considerable and I don't have the experience to risk it so no sand for me but I sympathise.

 

[mattylad]

Is the OP winding y'all up?

Has he not considered the extra weight that this will put on the joists when there are far better soundproofing materials available.
Such as the suggested Rockwool which will also aid heat retention, far lighter, easier to fit.

I can just imagine later on, the whole lower ceiling coming down & killing someone.
Nails holding it all up indeed.