ionionalanonalan wrote:
Thanks for that! So:
- Correct - I mix at a reasonable volume in monitors (so I make some noise, but not crazy amounts and never drums), so I guess I am mostly worried about sound from the outside;
- It's a timber frame build on a concrete slab. I can't figure out the size of the studs etc from the architect/engineer's drawings - bit confusing;
- Weatherboard is wooden planks (so I guess kinda like siding);
- Internal ceiling height is 2400mm.
- Not sure of what kind of roof/venting - from the diagrams it looks like it's just a flat roof on a slight incline.
- One window and one door. I'm getting a solid core door and a fairly small window.
Okay, so since you do not want to spend much more money you won't be able to have a double leaf assembly (a room within a room), however, your isolation needs are much smaller than normal so I would do a non-decoupled double leaf assembly, which means you still have two layers of mass separated by an air gap but the mass layers share the same framing. It should be sufficient for your needs.
From the limited info we have your biggest issues with keeping external noise out are going to be a few weak spots, such as the siding on your outer leaf. It's going to be super leaky due to the slight gaps between all the planks, and it won't be sealed airtight.
Sealing airtight will benefit you from a sound reduction point of view, if you could get your builder to seal all the joints with caulk from the inside before he puts the insulation and plasterboard on. He could also beef up the inside of the siding with a layer of OSB, then the insulation, then a vapour barrier, then 2 more layers of plasterboard. On the inside you would put your acoustic treatment. Note: The vapour barrier here is super important, don't skip it.
The next weak spot would be your possibly vented roof. Here you would need to leave a continuous ventilation channel (2"/50mm) under your roof deck, assuming you have vents at the eaves. The problem is this will let a lot of sound in. So here you could you could install some battens to the roof joists, fill above the battens with insulation (under the 50mm ventilation gap) install a vapour barrier on the bottom of the battens and attach two layers of plasterboards to the battens. Those plasterboard layers should be connected and caulked to the top plates of the walls, so the walls and ceiling are non broken and continuous.
If you have a warm roof, then that would be even better since you wouldn't need any ventilation. The rigid insulation would go above the roof deck and covered with a waterproof layer such as rubber. This will also help reduce footfall from birds and rain. You could install a couple layers of drywall straight to the underside of the roof deck, between your roof joists and then infill the remaining space with acoustic treatment. The ceiling is one of the most important areas to treat with thick, low density fibreglass insulation, so as much height as you can here is going to help you.
Make sure your builder does either a properly implemented vented roof or a properly implemented warm roof, anywhere in between these two designs and you will have problems with condensation, which will cause you to tear everything down and start again.
The next weak spot will be your window. You'll need some heavy duty glass such as laminated or toughened (tempered), 12mm thick should do. If you want the window to be openable then you will always have air leakage here as you won't be able to seal it. Also the framing of the window should be solid, not hollow or light such as uPVC. The seals are the most vital part of stopping sound coming in.
A solid core door is good here, make sure you have good seals all the way round the perimeter when the door is fully closed. Do not have recessed cavities for handles/locks, use surface mount handles and locks.
Lastly, make sure your builder seals every little gap/crack/hole with a non hardening caulk, especially where the sole plates meet the concrete slab. If he can he should put a rubber strip between the sole plate and the concrete slab, and a bead of caulk under the sole plates before bolting them down to the slab. Then more caulk around the edges. Same with door/window jambs. You're going to need some fresh air ventilation, which means you'll need to make two holes in your sealed up walls, but you'll build some silencer baffle boxes for each hole. These allow the fresh air in without compromising your sound isolation. You may want a mini split air conditioner as well for your cooling/heating.
Hope this helps,
Paul