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dpmiller

Isolation layers under pumped screed

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We're having 50mm of hemihydrate upstairs and down. Downstairs is standard polythene sliplayer over PIR, but I'm wondering what to do upstairs. Obviously there'll be a polythene layer, but are there any (reasonably inexpensive) products worth considering as an acoustic  barrier between it and the Caberdek below? Thinking in particular about some of the 2-3mm underlay rolls for laminate or such, but I see 5mm XPS being an option too?

 

Or is something like this a possibility, taping the overlaps instead of having a separate poly layer?

https://www.ebay.co.uk/itm/Laminate-Solid-Wood-Flooring-White-Underlay-DPM-25m2-x-3mm/161040149754?epid=1831830781&hash=item257ebdacfa:g:tBoAAMXQiNdRdp1l

... it's a local supplier...

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Your best insulation is below the floor 

Even a 25 mil isotec sound quilt will stop the sound bouncing around 

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Extra plasterboard on the ceiling below is the cheapest way of improving acoustic performance of the floor detail. Mineral wool under decking next-best.

 

I've tried premium underlays / thin resilient-layer types of products between floor finishes before and they make very little difference for the cost.

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We have a double layer of plasterboard on our downstairs ceilings with some (admittedly poorly installed) mineral wool batts above. I find noise transmission - especially impact-type - to be very bad.

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58 minutes ago, jack said:

We have a double layer of plasterboard on our downstairs ceilings with some (admittedly poorly installed) mineral wool batts above. I find noise transmission - especially impact-type - to be very bad.

 

True. For direct impact noise, the only thing that will really help is proper decoupling. Hanging the plasterboard ceiling on resilient bars will help to some extent but is a PITA to do. Even then, it's not exactly night & day difference (the one time I've done it).

 

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4 hours ago, jack said:

We have a double layer of plasterboard on our downstairs ceilings with some (admittedly poorly installed) mineral wool batts above. I find noise transmission - especially impact-type - to be very bad.

 

This is my concern and why I'm considering decoupling the mass of the screed from the structure beneath in some way.

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I think just having screed rather than chipboard will probably be where the main improvement comes. There's a lot more mass, which should reduce the noise somewhat.

 

Is there already caberdeck there? If not, I'd be trying to decouple that from the joists with something resilient.

 

Another important thing for sound reduction is airtightness. I'm convinced we get a lot of sound transmission through the service cavities on external walls, but I admit not being sure of exactly what path it would be taking between floors.

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I've found (by accident) that bonding bamboo flooring down with a fairly thick layer of Sikabond has made a significant reduction in impact noise.  Very little noise is transmitted through from the bedrooms and landing, whereas the bathrooms (which have 9mm marine ply glued and screwed to the OSB flooring, with 12mm travertine on top of that), transmit far more noise.  I suspect that the Sikabond MSP acts as a decoupling layer, as it's quite rubbery.

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Yup, the Caberdek is already down, factory glued into cassettes.

Certainly the couple of houses I've been in with screed upstairs have a very massive feel to the floor. We'll have a mix of floor coverings- carpet/wood/tile- to contend with but I'd tend to follow the same logic as @JSHarris that some level of decoupling is better than none.

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+1 to hemihydrate screed. They say it doesn't form a surface laitance like other liquid screeds so shouldn't be a problem sticking tiles. Make sure it doesn't get substituted.

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