Retro fitting Acoustic Insulation?

[jl9r]

Sorry if this is repeating a common thread.

We have recently purchased a new build detached house and noticing airborn noise between the upstairs and downstairs rooms. We also have a lot of joist movement noise, but the builders are coming back in a few weeks to remedy this by installing noggings. The ceiling / floor joists are engineered timber joists with chipboard above and 15mm regular plasterboard below. Nothing inbetween, just air.

As they are going to be ripping up the upstairs floors, we have an opportunity to install some acoustic insulation. I am thinking just some acoustic slabs at 100mm and 60kg/m^3 (RS60 or RW3).

My question is does anyone have any experience on doing this and how much effect it actually will make. I am nervous we do this at quite a bit of cost and lots of trouble and in the end the result is minimal. Is it worth the effort?

I am surprised that the part E regs do not cover detached builds at all....surely they still require airborn noise regs.

Thanks.

[PeterW]

If they are engineered joists then they potentially should have a strong back fitted not noggins. The boards should also be glued back to the joists which will stop creaking. 
 

I would expect the builder is expecting to just slice a gap through the middle of the rooms and take out part of the floor and put a row of noggins through the middle of the room. That won’t give you much of a gap to get insulation installed. 
 

Have they confirmed the schedule of works to fix the floors ..?

[Bitpipe]

It's very difficult to eliminate noise transfer, you need to contend with low frequency transmission, usually through solid materials and higher frequency transmission which goes through air.

 

I got to know a self builder (used to post on this site's predecessor) and his new build was designed to reduce noise - resilient wall bars, thick rubber acoustic matting, lots of rock wool between ceiling and wall joists, sound block PB etc. Spent a fortune.

 

It made some difference but not enough for him. Ultimately unless rooms are airtight and isolated from surrounding structures then there will be noise transmission.

 

It's concerning that there is no acoustic insulation between your ceiling and floor, that should be a minimum. We used blue sound block PB on our basement ceiling and GF ceilings but there is still noise transference, probably less than if we used regular.

 

So I'd be inclined to do what you can but don't overspend.

[ProDave]

Don't forget "engineered joists" also includes JJI I beam joists.

 

This sounds like a typical new build where it was done properly on the one house that was inspected for building regs and all the corners cut for the rest..

[jl9r]

Thanks for the replies.

 

PeterW - the joists are the I-beam type with 'cardboard' between the small timbers. The builders say we didn't need noggins but the amount of creaking and movement has led them to now have to install them on most of this house type now. You are correct, they were only going to cut out a 300mm strip, enough to put the 4" x 2" noggins in but I have asked they widen to at least 600mm. This should allow enough to slide in the acoustic slabs.

 

Bitpipe - yes they should and other builders have said it should have sound board as a minimum,  but "value engineering" dictates it is all done as cheap as possible and then try and do as little as possible to fix it if it goes wrong.

 

ProDave - yep!

[nod]

100 mil 

acoustic will greatly reduce noise 

 

 

[jl9r]

Thanks Nod. Is this from experience of before fitted sound travel and after fitting the mineral wool?

[Russell griffiths]

Tbh I don’t think you stand much chance of sliding in anything, the first obstacle and the acoustic roll will bunch up and stop. 

 

[AliG]

I was going to say the same thing. The ceiling space will be full of pipes, cables and, knowing builders, rubbish. So you won't be able to slide stuff in.

 

Do you know someone who has had the noggins installed and has it worked? It might be that they should be that they need to attach the floor better, indeed they will weaken the floor by cutting a strip out of it.

 

I would try and get them to agree to take up the floor to put in the noggins. They you can get in the insulation and they can fix it down with glue and screws. I would maybe offer to pay part of the cost as it is non standard as far as they are concerned.

[MJNewton]

Is fitting of noggins to I-beams standard practice / needed? I don't recall seeing them in product literature, but perhaps it's just that I haven't been looking for them.

 

I'm surprised there aren't resilient bars fitted, as I assumed they were a standard fit now given that even our 2007 Persimmon house has got them. 

Edited July 29, 2020 by MJNewton

[Temp]

12 hours ago, jl9r said:

The ceiling / floor joists are engineered timber joists with chipboard above and 15mm regular plasterboard below. Nothing inbetween, just air.

 

I'd be very surprised if that meets building regulations, specifically  Approved Document Part E. There are several ways to demonstrate compliance. One is to carry out a sound test. Another is to design and build to match a so called "robust design" which is a design someone else has built and tested. That might be the company that supplied the floor joists or the sound insulation they failed to fit.

 

I would ask the builder how they demonstrated compliance with Part E to Building control. Ask which route they took to demonstrate compliance. If you appear knowledgeable  they might give in an fit insulation that probably should have been there.

[ProDave]

23 minutes ago, MJNewton said:

Is fitting of noggins to I-beams standard practice / needed? I don't recall seeing them in product literature, but perhaps it's just that I haven't been looking for them.

 

I'm surprised there aren't resilient bars fitted, as I assumed they were a standard fit now given that even our 2007 Persimmon house has got them. 

Mine had them. The "noggins" were just short bits of the same I beam construction.

 

Here's the ground floor being assembled with some in place already.

 

[MJNewton]

Ah yes, and indeed they don't look out of place. 

[jl9r]

 

40 minutes ago, Temp said:

 

I'd be very surprised if that meets building regulations, specifically  Approved Document Part E.

Apparently part E sound regs do not apply to detached houses?

 

3 hours ago, Russell griffiths said:

Tbh I don’t think you stand much chance of sliding in anything, the first obstacle and the acoustic roll will bunch up and stop. 

 

The acoustic insulation wouldn't be on a roll, it would be the higher density slab type and have heard it does push in.

 

The builders (Persimmon) are doing the same noggin for job to many houses on the site and apparently other sites now. The ones i have spoke to say it has totally fixed the floors, no creaking and way more solid feel.

Like I said before, you can value engineer a job down to save cost, but go too far and you have to accept rework cost - that's what they are having to now do.

[Temp]

16 minutes ago, jl9r said:

Apparently part E sound regs do not apply to detached houses?

 

Last I looked they do. As I recal..

 

Part E1 applies to separating walls (for example walls and floors seperating dwellings such as the party wall between semi detached houses and flats) and

Part E2 applies to walls and floors between rooms within the same dwelling.

 

Your floor/ceiling should meet part E2, which isnt as difficult as E1 but still exists unless I'm out of date.

 

Edited July 29, 2020 by Temp

[jl9r]

Thanks Temp. I need to find out more about the regs cos it was the builders that told me it didn't apply to detached. Must admit, I did read the regs and couldn't see anything that said that was true...?

[Temp]

Did they put that in writing?

 

[jl9r]

8 hours ago, Temp said:

Did they put that in writing?

 

Yes in an email. They also attached a test report from the joist manufacturers saying the I-beam make up with 18mm chipboard and 15mm PB conforms to part E regs and drops 40dB.

I asked for the pre completion certificate for our site, as per the regs, and no reply. I even tried asking local building control and got no reply.

 

[dpmiller]

Conforms *without* any acoustic roll?

[MJNewton]

23 minutes ago, dpmiller said:

Conforms *without* any acoustic roll?

 

The JJ I-Joists Technical Manual confirms (pg 9).

[jl9r]

This is what they sent me.

Hickman Noise Resistance.pdf

[MJNewton]

Noting that they specify a 15mm plasterboard, would 12.5mm plus a 3mm skim be expected to perform to the same level? Asking for a friend... 

[Temp]

Im surprised  they achieved part E2 without sound insulation but that's what the joist manual is saying. Standards in Scotland are higher. 

 

[AliG]

The 40db minimum reduction is a very low target. Achieving this will not stop noise transfer.

 

This is one of the few areas where there is a big difference between the Scottish and English regs. The 43db minimum target in Scotland requires 22mm osb glued and screwed and accoustic roll.

 

It would be hard to build a ceiling with much less than 40db of noise reduction.

[MJNewton]

  

2 minutes ago, Temp said:

Im surprised  they achieved part E2 without sound insulation but that's what the joist manual is saying. Standards in Scotland are higher. 

 

 

I guess it's the nature of I-Joists, and their thin webs in particular? 

Edited July 30, 2020 by MJNewton