Insulation

Optimal thickness of Rockwool for separating floors (timber joist cavity)?

Anonymous user 03/03/2024 - 2.53 PM

I've got 2 questions about Rockwool / Acoustic Mineral Wool (AMW) and soundproofing my flat. I've got a ground floor Victorian semi-detached maisonette and I'm looking to install some soundproofing above my ceiling boards. The upstairs flat has their floorboards laid directly on the timber joists, so I know that I'm not going to get rid of the sound completely. I would like to use Rockwool flexi 1200x400 as the joists are roughly 400mm apart, and these slabs would fit into the cavity. I have done the measurements and I know that I need 64 slabs in total for my bedroom and lounge. 1) My first question is about what thickness of slab I should get. I realise that if money were no objection I would go for the 100mm / 140mm slabs; but that is sadly not the case. I want to know if there's a very big difference between the 50mm and 60mm slabs in terms of sound dampening. 2) Does anyone know where I can get these size slabs from at a reasonable (i.e. lowest) price from? I've noticed that the size that I want isn't readily available, but that a lot of suppliers only stock the 600mm wide slabs, which would mean a whole lot of cutting to size and therefore a LOT of waste. Thanks, in anticipation of many good, helpful answers :)