I've completed one of these in the past few months here at Cymbalise HQ in Reading. I went for a brick and block built room, measuring 5mx4m with 100m insulation in the wall cavity. I got a builder to lay the slab and build me four walls and a roof. I then did absolutely everything else.
What you need to know:
- Planning is an issue. Permitted development allows you a maximum of 30m2 surface area (not a problem), provided you don't use up more than 50% of your external garden space. You're allowed a maximum height of 2.5 meters (thats externally, to the max pitch of the roof) This is lower than you might think when you actually really sit down and consider what you need internally and the construction of the roof before you even begin to contemplate soundproofing. If its going to be built on the boundary then you have to pass building control [in practice this basically comes down to ensuring its built out of something that isn't flammable]
You're not allowed any plumbing in the building, no aerial anywhere near it, nothing that could be slept on inside.
Meet these criteria and you can crack on without paying for any planning permission. Otherwise you're looking at between £600-900 for all the planning steps to be paid for.
- I also wanted a room within a room. However practically this is VERY difficult to construct, particularly if you're doing it yourself, unless you're a builder or carpenter by trade. I very quickly realised this sort of construction was beyond my capabilities and went for conventional soundproofing instead. If you're hell bent on room within a room, you want a minimum of 100mm gap in all dimensions. This makes your already small(ish) room even smaller, because as well as the gap you've also got the thick internal walls. These 100mm's all creep up on you - gap, rockwool, studs, 2x4's, plasterboard etc - and before you know it you've lost 1m in all dimensions. Now find somewhere for your drumkit...
- Acoustic rated anything is a) expensive and b) heavy. Very heavy. You'll need a good mate or two to assist.
- Don't buy anything from an acoustic materials supplier. You can get everything you need from a builders merchants at a significant discount.
- The roof. No matter how thick you make your walls if the roof isn't similarly thick then you've just wasted lots of time, money and sweat. I researched the various options thoroughly and they were all WAY too expensive. In the end I went for block and beam (usually used for floors), with a double layer of blocks on top. It works. And it keeps the height of the flat roof down (remember the height restriction...)
- Steer clear of green glue, genie clips, and anything else that claims to reduce noise by significant percentages. They are VERY expensive for what they are and the same money spent on a second layer of acoustic plaster board or resilient bars (from a builders merchant, not an acoustics shop. Exactly the same thing at literally a fraction of the cost) will reap significantly better rewards.
- Home made bass traps are a) incredibly easy to build and b) very cheap. Diaphragmatic ones even more so. I saved £100's doing it this way.
- Don't install a window or a door. Regrettably if you don't have a door you can't get into it, but it'll be a lot more acoustically isolated (there is no such thing as soundproof in the real world). So you may have to have one. but don't install a window. If you absolutely have to have a window and a door, welcome to your biggest headache, bar none. I solved the problem by building an independent stud wall (the only such in the room) with a 100mm gap behind the block and brick wall with the external door in it. This internal stud wall had another door and window (I know, I should have taken my own advice and binned the window...) behind the external door and window. The windows were both second hand triple glazed units (£60 each - bargain!), the external door is steel with fireboard inside, and the internal door a firedoor, with slabs of plasterboard screwed on both sides.
They're still the largest source of noise leakage. The door and window frames have been heavily treated and sealed to an inch of their lives.
They're still the largest source of noise leakage. Don't install a door or window.
- Don't get me started on ventilation. A sound isolated room is also a completely sealed one. Letting in fresh air lets out sound. Lots of sound.
- I've had a noise survey done, now that its complete. Approx 105-110dB inside, down to around 55dB about 3m away outside. Two people holding a conversation at a reasonable level 3m away from the room are louder than the noise coming from inside the room.
- It ain't cheap. Total cost came to around £13,000
Customers selecting cymbals do so at all hours of the day, night and weekends, testing countless combinations on the drumkits in there.
My band use it as well at full volume. You would be hard pressed to tell when a customer, my band or just little ol' me was in there.
Job done.
I'm incredibly happy to talk about the build and offer as much help as I can. Like you I found barely any real, practical experience and assistance, and had to learn as I went along.
Any questions just ask! Or pop down to Reading and take a look. The results are unbelievable and worth every second of blood, sweat and tears.