Floor sound insulation question, plasterboard and ply

[IanWood]

Hello all,

We moved into our first floor flat Sep 2008 and noticed the master bedroom's carpet was raised by around an inch and horrid - so we binned it .

After removing the carpet and underlay we noticed that there was plywood with what looks like plasterboard underneath.

This was put down by the previous owner to improve sound insulation. I understand from the owners below that there were problems with sound insulation and the downstairs flat put more plasterboard on their ceiling.

In our bedroom the boards were taken up and insulation put underneath, then plasterboard and then plywood put on top of them. This extra material has raised the floor by around and inch, which isn't a problem in itself expect that its different to the rest of the flat.

My question is, is it likely that the plasterboard and plywood would make much difference to the sound insulation? If not we would like to remove these layers and put carpet down. If it is likely to help we may consider doing the rest of the flat in this manner.

Unfortunately I have been unable to find out if thermal insulation was used or proper acoustic insulation. From the quality of other work he had commissioned I wouldn't be surprised of the cheapest materials had been used.

At the moment we can still hear the occasional noise from below, their kitchen is below the bedroom and with their tile floor we can hear chairs been scrapped etc. There is also a chimney breast in our room which may be transferring noise?

My plumber recommend this for sound insulation http://www.knaufinsulation.co.uk/products/glass_mineral_wool_rolls/acoustic_rolls/acoustic_roll.aspx which I imagine would be far better than the stuff normally used in lofts.

Sorry for such a long post but I have no idea how to proceed, my question is basically can I rip up the stuff on top of the boards and fit carpet or is it likely to be helping with sound insulation? Another option would be to replace the hopefully normal insulation with the stuff I mentioned above.

Hope someone can point me in the right direction.

Thanks in advance,

Ian

 

[freddiemercurystwin]

The plasterboard and ply combo will be better in terms of increasing sound insulation than carpet alone.

The level difference can be easier to live with if you have a timber transition strip made up.

 

[IanWood]

Thanks for your reply - I was hoping people would come back and say rip it up .

The level difference can be easier to live with if you have a timber transition strip made up.

For those who don't know what that means please could you elaborate!

Is it likely that sound could travel up the chimney breast in the room?

Cheers

Ian

 

[mointainwalker]

My plumber recommend this for sound insulation http://www.knaufinsulation.co.uk/products/glass_mineral_wool_rolls/acoustic_rolls/acoustic_roll.aspx which I imagine would be far better than the stuff normally used in lofts.

I think you are highly likely to be imagining wrongly then. There is no real technology involved in acoustic fibre-wool sound-proofing, just compressing the wool to make a denser block.

The product quoted supposedly weighs only 10 kg/m3 ( which actually seems light even for thermal insulation ) and is in a roll so is not compressed at all. I think this is their normal loft insulation re-packaged - they even use the same photo for the two products !

I would not take what your plumber says as an expert's comments: sound-proofing is rather difficult involving a number of different steps.

Is it likely that sound could travel up the chimney breast in the room?

Yes, it is very likely.

 

[freddiemercurystwin]

This is simply a profiled timber threshold strip that ramps up from one level to the next so there isn't a 1" step. You may have something like it already of course.

Sound will be travelling up the chimney, it will also be passing through the walls, as well as through the floor.

Sound is one of those things, what's acceptable to you may be unacceptable to the next fella and vice versa. Therefore whether you or your neighbour would still find it acceptable cannot easily be predicted. Its not an easy thing to measure.

 

[IanWood]

My plumber recommend this for sound insulation http://www.knaufinsulation.co.uk/products/glass_mineral_wool_rolls/acoustic_rolls/acoustic_roll.aspx which I imagine would be far better than the stuff normally used in lofts.

The product quoted supposedly weighs only 10 kg/m3 ( which actually seems light even for thermal insulation ) and is in a roll so is not compressed at all. I think this is their normal loft insulation re-packaged - they even use the same photo for the two products !

Is it likely that sound could travel up the chimney breast in the room?

Yes, it is very likely.

I didn't notice that they use the same photos!

I think I will look to see if the chimney is playing a part.

 

[IanWood]

This is simply a profiled timber threshold strip that ramps up from one level to the next so there isn't a 1" step. You may have something like it already of course.

Sound will be travelling up the chimney, it will also be passing through the walls, as well as through the floor.

Sound is one of those things, what's acceptable to you may be unacceptable to the next fella and vice versa. Therefore whether you or your neighbour would still find it acceptable cannot easily be predicted. Its not an easy thing to measure.

Thanks for the picture, looks really good.

You are right about the sound, most of the time its not a problem - rarley is to be honest. But, what I don't want to do it rip up that stuff and cause a problem. If possible I would prefer the flat to be on one level. For one thing it would look odd when we come to sell it.

On the other hand, we could re carpet the whole flat and put similar material down all over the floors. Is the plasterboard and ply better than insulation, I mean I we were to put the plasterboard and ply down over the whole flat would it be worth putting insulation down underneath too?

The thing I want to do it get a normal looking flat, at the moment we have the ply on the floor in the bedroom and carpet elsewhere. Some floor boards creak so I want to deal with those anyway. Sound isn't too much of a problem at the moment.

Thanks again all for your help so far,

Ian

 

[mointainwalker]

Is the plasterboard and ply better than insulation,

We can't say. Sound diminution levels for ordinary products not freely available and it is anyway a rather specialist field.

I mean I we were to put the plasterboard and ply down over the whole flat would it be worth putting insulation down underneath too?

It would undoubtedly be better, but whether you would think it worth the extra work and expense ????????????????

 

[IanWood]

Is the plasterboard and ply better than insulation,

It would undoubtedly be better, but whether you would think it worth the extra work and expense ????????????????

That's the hardest thing to conclude - given how hard it would be measure the before and after results, i.e. is it quieter now because of the work or because they are now longer being noisy.

I imagine it would be very hard work and quite disruptive - certainly not relishing it.

Thanks again,

 

[freddiemercurystwin]

Well firstly presumably it didn't put you off buying it so that may be a moot point.

My experience of converted flats (is it converted or was it built as flats) is that sound insulation is usually pretty bad, if you do not hear much from your neighbour then that must be a good sign I guess although you neighbour could be quiet as mouse! Anyway the point I'm making is that it sounds like the PB/PLY combo is largely working OK so you could do worse than to adopt that through out especially if you are determined to solve the creaks and avoid a small step up into the bedroom anyway.

The insulation is their to stop ambient sound like voices rather than impact noise like doors slamming. Probably worth doing if have the boards up anyway as its cost is not that great.

It really comes down to the individual though where sound insulation is concerned.

 

[IanWood]

Yes, it is a converted flat. Didn't put us off as it was a much larger flat then others we had seen for a similar price.

I am coming around to the idea of the PB/PLY over the rest of the flat. Would defo make the floor boards more even and hopefully be able to sort of the creaking boards at the same time.

Still undecided if want to lift the boards, in the bedroom the PB/PLY is on top of the boards, not replacing them if I was unclear.

If I was to put plaster board and ply down would I need to raise the skirting to leave an expansion gap or could the gap be covered with the carpet and underlay?

Thank again,

Ian