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Rockwool, and lots of it


Weebles

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After reading every post on this forum on the subject of sound insulation and in particular Rockwool I wanted to document our experience.

 

Until the delivery arrived and we opened the packets we really didn't know what we were going to be working with.  Here is the best description I can give.

 

We ordered the following from Insulation4Less.  They told us the lead time was about 4-6 weeks (nationwide shortage) but actually it all came within a week leaving us with a literal mountain of rockwool to store around site.  It was wrapped but needed to be lugged into the house out of the rain.  Big job.  The 50mm deep packs were orginally intended to go in the ceilings where there were lots of pipes to fit around.  

 

 image.png.ec46d2a6eaf78933b1615501a3772026.png

 

We chose RWA45 rather than the more expensive Flexi.  Having not seen the Flexi I can't give a really accurate comparison.  But the RWA45 is flexible and can be pushed into spaces and compressed a little anyway.  And it is cheaper.  It is not rigid / solid like Celotex (which I had first thought it might be).

 

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Here are some open packs.

 

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It is pretty easy to cut using an insulation saw like this.

https://www.screwfix.com/p/bahco-insulation-saw-22-560mm/7498k

 

But it does shred easily too.  Mask and gloves absolutely essential.  The 100mm deep stuff looks like this.

 

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So although it comes in these "batts" which have a form to them, you can trim to to the size you need.  We are trimming almost everything because the 600mm wide batts don't fit into the 560mm gaps between the 600mm centred studs.  But there are plenty of places to stuff the offcuts and the puzzle of how to use every offcut as efficiently as possible is keeping us both amused somewhat.

 

We are fitting this into all the stud walls (internal) and the ground floor ceiling.  No need for any insulation on the external walls or top floor ceilings as that has been pumped in by MBC (more of that in another blog).

 

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Hubby used our MVHR builders straps to fit up a load in the ceiling.  He is now using cheap pallet strapping and a staple gun!

 

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It is fair to say that we have been doing this sound insulation on and off now for well over a month.  It is a big job.  Ceilings harder than the walls. Time consuming.  A bit (alot) messy.  Requires us to ply the walls first (where ply is needed) and then insulate.  For the stud walls that don't need ply we will work as quick as we can in the evenings once the the plasterboarders are on site (due next week) filling in behind them as they plasterboard one side.  Going to be a busy week.  But progress is satisfying and physically working on our build again is fun.  

 

 

  • Like 4

18 Comments


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Great job ! I have used this between my two floors and I really like the product, I find cutting it with a long VERY-sharp knife to be the easiest and cleanest way. I have recently been given 30 rolls of acoustic insulation which is more flexible...... not nearly as nice to work with but it was free as the ends had got damp during a deliver to the builders merchants and they just wanted rid off it. It will take a bit more care to place and hold but hay ho. Currently in the windy  shed raised of the ground drying...... 

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Blimey, it's like a mirror image of my place in December!

 

I bought mine from Condell Ltd who were very competitive on the price.

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Good job.

 

For cutting I have usually used a traditional wavy-edged bread knife. I do wonder if sheep shears would be good for the job.

 

For fixing I usually just staple gun straight through a corner of the insulation ... to eg fair I have not used batts, just rolls.

 

F

Edited by Ferdinand
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I'm surprised that the difference between RWA45 and RWA6, which I used, is so significant. The RWA6 is rigid and from the data sheet the kN/m2 for 10% compression is 3.0 for RWA45, and 28.2 for RWA6.

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we've done the same as you - for the 50mm stuff I just use a stanley to cut it.  I've wedged it up by using old bits of offcut wood - needed a clean out so it was a good recycling win.  As some point I will need to find some cheap strapping.  I would put that insulation in the walls before boarding if I were you - easy enough to do & it will save you time when the boarders arrive.

 

Looking good.

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if you are doing the ceiling for sound insulation, from my experience, sound will always travel via gaps and holes. if you have spot lights, should will travel.

 

Also, i noticed the rock wool can't get into the space with the metal easi-joists. Sound will travel. however, you have enough to at least deaden/dampen the sound (echoes etc).

 

I was very diligent with the bathroom above the living room but did not put rock wool in some section under the shower tray due to the pipes, you can hear the shower.

 

just a opinion.

 

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17 hours ago, jayroc2k said:

Also, i noticed the rock wool can't get into the space with the metal easi-joists. Sound will travel. however, you have enough to at least deaden/dampen the sound (echoes etc).

 

I did wonder about the joists. And TBH the space above the walls between rooms that sits below the ceiling insulation. We are putting it everywhere we can so hope the sound is deadened, as you say. 

Finished the walls this weekend. I am fed up of Rockwool now. Still got to finish the ceiling......

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Ive put some in the metal web joists as well.  Under some of the soil pipes etc i'm going to double plaster board (so one layer is in the ceiling void just on top of the ceiling layer) as well as trying my best to insulate around them. I may even put some clay plant pots where the leds go and then insulate around them well.  I'm using 15mm pb on all ceilings in another effort to reduce noise. 

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22 minutes ago, CC45 said:

I'm using 15mm pb on all ceilings in another effort to reduce noise. 

 

My only regret with my new build is the sound transference between floors (12.5mm Pb) with  Rockwell between that and floor, should have double boarded it at least.

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We are also using 15mm PB on all ceilings.  Hope it helps.  And we will stuff any spare Rockwool into those metal web joists.

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so from the top down we have 22mm chipboard then 50mm of rockwool RWA45 sound insulation & then I've put in 100mm of sound reducing insulation roll (given to me free of charge) & then 15mm PB.  Inside the metal web joists also filled with some of this roll.

 

Missus has been up stairs and created some noise and even without carpet the sound reduction is pretty impressive.

 

Double boarding with 12.5mm would be another way of really cutting down the sound.  We will make this decision just before skimming - easy enough to throw another layer on if we want.  We've got plenty of height downstairs.

 

I like a quiet house. 

  • Like 1
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10 hours ago, CC45 said:

I like a quiet house. 

So from the top down.....

 

Final floor not laid yet....

22mm chipboard glued and screwed and compressed onto “no squeaks” silicon on top of each floor joist

50mm void

50mm acoustic rock wool roll

100mm RWA45

50mm rockwool 

vcl

12.5mm standard plasterboard

12.5mm sound block plasterboard x 2 layers......

25mm void and battens

10mm tonge and groove cladding 

all layers sealed with acoustic mastic round every joint........

 

the reason for x3 layers of plaster board was one of my volunteers picked up the wrong stuff and we had already got the first layer up before spotting this. I always wanted two layers of soundblock so I just got on and put them up as well......  needless to say the additional ceiling  build up has now caused us some loss of head room and this is dictating the floor build up.....  but that’s a long way off still. 

 

This is is a tiny traditional cottage so low ceilings are not really a problem, still going to be over 2.2m just.......

 

i still have a gaping hole where the stairs used to be  so I can’t test the effects of this build up yet, but one would hope it does the job. 

I should have used a special de coupling system for at least one of the layers of plaster board but it was all done when I was still living in the dark ages......

ebuild and then Buildhub enabled me to drag myself into the light.

 

everydays a school day 

 

 

 

 

 

 

  

 

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I doubt anyone will top that lot - it must be exceptionally quiet in there!  Not too sure I would spend that much.  Good effort.

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My victorian house has one section with plasterboard and the second with original lathe and plaster (same reception with two rooms above). I have to say, 2 plasterboards ( I used the heavy fire board version) is still no match compared  to the lathe and plaster.That should give some perspective as to how poor plasterboard is at sound insulating/deadening, hence the need to decouple and use 2x sound bloc 

 

for now, I don't mind, i like to hear what my kid is up to, I may change my mind when she start playing whatever the futuristic version of teen pop is in 10years time. Hopefully, there will be a "Sound Bloc in a can" spray i can buy and just spray the ceiling...

 

 

 

 

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On 28/01/2019 at 15:20, joe90 said:

 

My only regret with my new build is the sound transference between floors (12.5mm Pb) with  Rockwell between that and floor, should have double boarded it at least.

Hi Joe, a bit of an old post, but out of interest, what did you add between your floors to be disappointed with the results? I have a similar post looking at decent ways to reduce sound between floors and stud walls without going over the top.

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44 minutes ago, ruggers said:

Hi Joe, a bit of an old post, but out of interest, what did you add between your floors to be disappointed with the results? I have a similar post looking at decent ways to reduce sound between floors and stud walls without going over the top.

Floor void was filled with 150mm of sound (wool like) insulation but although it met building regs I find it very poor, as I said before I regret not double boarding or/and sound bars. I have 20:20 hindsight and hope others will gain from my comments. Plasterboard is not expensive in the scheme of things.

Edited by joe90
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@joe90 Thanks Joe, 150mm is a decent amount too, I'd be disappoint to and wasn't going to put any more in. I'd be interested to know if doubling up the boards would make a lot of difference or if it's just expected to make an improvement, I've added much thicker boards in the past 25mm and wasn't overly impressed. Sound bars are supposed to really help, maybe even work out the same as double boards.

 

Are your rooms above carpet & underlay or hard floor?

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8 minutes ago, ruggers said:

Thanks Joe,

Carpet upstairs with underlay, voices and tv can be heard in bedroom above more than I hoped. From reading I get the impression “mass” is the best sound absorber and no sound gaps along with de coupling (sound bars) others will give their view I am sure.

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