Practice room in an apartment building

I'm looking for a bit of sound isolation advice and general thoughts on my own plan thus far: I'm turning a 6.5m x 4.4m (21ft x 14ft) living room on the 4th floor of a 1920s brick house into a music practice room (classical instruments - mainly strings, singers, winds, piano). The house itself is pretty solid, typical early 20th century Amsterdam brick house. Only adjacent neighbours are below us, side walls are staircases. Currently the sound isolation is pretty decent, we hardly ever hear our neighbours. Regardless, we'd like to improve on the situation within a reasonable budget (and we're fully aware true isolation costs a fortune). I've done some reading up regarding various products and options and have decided to give Green Glue a go, but am doubtful about some of the other components. My current plan is something along these lines: Rip up old laminate + underlay (layer of foam and a layer of some sort of soft fibreboard). Underneath is the actual subfloor, pine planks. On top of the planks I'm thinking of installing first a high density rubber mat, then 18mm (3/4") OSB, green glue, 18mm OSB. Then put screws through the OSB sandwich that won't reach the rubber mat. The floor finish will be glue down cork. For the walls - a layer of green glue + drywall on top of the existing walls. As I mentioned above, I'm not looking for any miracles here, just a reasonable improvement over the current situation. I've read a few forum posts here, at Gearslutz and at AVS forums and have seen similar configurations used a number of times with what appears to be a reasonable degree of success. There's a few issues though: Suitable rubber matting seems to be almost impossible to source in the Netherlands and international shipping costs for something that heavy make this option a little less appealing. A couple of times I've seen people recommend 'soundboard' for a similar decoupling effect and after some research figured out that this material is basically cellulose fibreboard, but again I've been unable to find any for sale in the Netherlands. Are there any other alternatives that could work for this purpose? I've seen a few people suggest a layer of rockwool or similar, but others seem to be strongly opposed to this approach.. Anything else I'm missing or getting wrong? Any kind of input would be appreciated! Thanks in advance!

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things! :) It sounds like you are trying to isolate or "float" your floor on a rubber mat, but in reality what you are proposing won't work. Here's why: viewtopic.php?f=2&t=8173 Despite what you see on the internet (especially the poor misguided many on YouTube!), that simply does not work. There are ways of isolating a floor, but not like that.

I've seen a few people suggest a layer of rockwool or similar

Exactly. That's the "drum riser" approach, and does work reasonably, if done properly. It works MUCH better than trying to float the floor on rubber... - Stuart -

Apologies and thank you for your reply Stuart! Indeed, I got the idea for the rubber mat mostly from AVS & soundproofingcompany.com, but saw it being recommended over and over again, which led me to think it must do something. Rockwool would solve a lot of my problems - it's cheap and readily available. What kind of density would be most suitable for this kind of application? There's 100kg/m3 and 140kg/m3 floor sheets available in 20-50mm (load bearing capacity at 200kg/m2 and 400kg/m2 respectively) What kind of thickness should I be aiming for? One thick layer or several thinner layers with staggered seams? Another product that a contractor that I spoke to recommended very highly is a product that consists of 18mm of gypsum fibreboard on top of 10mm of rockwool. I'm slightly sceptical about the product and can't find any reviews either... Thanks! Edit: one further question comes to mind - with a product like rockwool, am I in any danger of creating a triple leaf?

Here is some further information: Room height - 2.55m Budget - I'd prefer to stay below €2000 for the floor (not including the top surface), but there's a fair amount of flexibility if necessary. Sound levels - these could vary a lot depending on the instrument configuration and I currently have no measurements as we've not started rehearsing in this space yet. Like I stated in my original post, it's classical instruments and singers only, up to 4-5 musicians at a time. I've also included a drawing of the room as an attachment here. Please let me know if there's anything else still missing and thanks for your help!