Composer Studio - new build

[holymoses]

Hi there - first time post here...! The

I'm building an extension on the back of my house for a new, single room Composer studio. I need to soundproof the room before treating and would be happy with 50db or so of isolation. I record guitars too, both acoustic and electric so record ranging from the odd very quiet harmonic and to medium to loud electric. I have kids that play in the garden where studio is situated, a neighbour with a loud dog so don't want to hear those guys either!

The room is attached to the house by one wall and has dimensions of:

7260 x 5900 x 3300 Height. There are two 800x1600 windows either side of double, or 'French' doors (the reason for the doors being that I'd like to future proof the studio for use as a garden room or such when we come to sell sell the house!). They are on one long side of the building. I have a very high vaulted roof that is slightly unusual in it's shape - a 'Crown' roof. It has a steel frame and is capable of taking a lot of weight (as per my instruction to the Structural Engineer).

The foundations had to be made deeper because of trees proximity to the build, so I now have a concrete 'beam and block' floor.

So UK Building Regulations say I have to have a double-skinned wall with insulation... I have a heavy block on the exterior side, 10cm of rockwool insulation, and then a light weight block on the inside skin. I know that in an ideal world I should only have a single wall construction but I have to work with what I've got! Building Regulations also require that I have 750mm of insulation on the Floor and 650mm of screed on top, so barring any alterations, that is what I have to build on.

What I'd like to do is build an angled, shaped room from wooden stud work around the whole room, not touching the walls anywhere, making provision for some secondary doors and windows. Then, currently, the plan is to fill the stud with 60kg 75mm rockwool, attach GenieClips, furring strips and then two layers of 15mm acoustic drywall separated with a membrane product called TecSound SY 70 that has a good deal of mass.

I'm then looking to build a ceiling, and this is where I'd like some advice please... I have an aircon unit to install with ducting so I'd like have room to build that in, and also I'd like to pitch the ceiling in places to take the height down and not to be parallel to the floor. I'm going to use the same GenieClip system again with the ceiling I think.

What would be the best way to go about this? Can I build the ceiling INSIDE the room-in-room walls, if I build the shaped wooden stud by screwing into the wall studs? Do I need to suspend that much weight to the roof joists in some way (knowing this would cause flanking transmission) as the structure and aircon/lights would be quite heavy?
Is there a way to safely build a ceiling on top of (and supported entirely by) the stud walls so it doesn't touch the roof at all? How do you make a structure like that safe from collapsing if it is freestanding?

Many thanks in advance for any help - pictures attached...

Tonus

[holymoses]

Forgot to add the pictures - see below

[Soundman2020]

Hi there Tonus, and Welcome!

I need to soundproof the room before treating and would be happy with 50db or so of isolation.

Great! 50 dB is doable. It's at the higher end of what can be accomplished in typical DIY construction for a home studio, but you are on the right track with your plans so far.

7260 x 5900 x 3300 Height.

That's a nice size for a home studio, especially the high ceiling.

There are two 800x1600 windows either side of double, or 'French' doors

That's fine, but you can't just use any old windows / door there, if you aim to get 50 dB of isolation. You will need acoustic rated doors, which have a single pane of thick laminated glass and special seals. They are heavy, and expensive. Typical doors that you buy in a hardware store will not do the job: you wouldn't get much more than about 40 dB from that, tops.

So UK Building Regulations say I have to have a double-skinned wall with insulation... I have a heavy block on the exterior side, 10cm of rockwool insulation, and then a light weight block on the inside skin. I know that in an ideal world I should only have a single wall construction

I'm assuming that the two leaves of that wall are tied together with steel ties in many places, so that would probably be more like a coupled 2-leaf system, and there's lots of mass in those concrete blocks, so you should be reasonably OK there. You might need to beef up the final inner-leaf a bit to improve low-frequency isolation, but you'll find out if that is necessary when you do the math.

What I'd like to do is build an angled, shaped room from wooden stud work around the whole room, not touching the walls anywhere, making provision for some secondary doors and windows.

The idea is right, but why do you want to angle the walls? It's a common myth that you need to do that. There MIGHT be reasons for it, such as if you are building an RFZ style control room, but that doesn't seem to be the case. Why did you want to splay your walls?

currently, the plan is to fill the stud with 60kg 75mm rockwool, attach GenieClips, furring strips and

... If you have a fully decoupled wood frame, then you do not need to decouple it again with clips! If you already soaking wet at the bottom of the swimming pool, you can't get any wetter by taking a bucket of water with you as well! Ditto here: decoupled is decoupled. Forget the clips and hat channel, and save yourself some money. You only need those for walls that are not decoupled.

then two layers of 15mm acoustic drywall separated with a membrane product called TecSound SY 70 that has a good deal of mass.

Drywall has a good deal of mass, and is a lot cheaper than exotic products like that! The equations that describe how well a wall isolates have two major variables: mass, and air gap. There's no place in the equations for inserting the cost of exotic mass. It makes no difference. Sound waves cannot read price tags, so they don't really care how much you paid for the mass... all they care about is the total amount of mass in front of them. They aren't at all picky about what materials went the mass... So it makes sense to buy the cheapest mass that will do the job... in most places on Planet Earth, that is plain old ordinary drywall. You don't need to pay high prices for strange products that have lots of mass in them, when cheaper mass is readily available and affects the sound waves in the same manner.

I'm then looking to build a ceiling, and this is where I'd like some advice please... I have an aircon unit to install with ducting so I'd like have room to build that in,

You cannot put that in the ceiling cavity, since you'll never have access to it again after the studio is built: you'd have to break a hole in your ceiling to do maintenance and repairs. The AHU needs to go some place where you can get to it easily, and it needs a lot of space around it for installation / maintenance / cleaning / repairs. The manual will show you how much space you need to allow on each side for that. I normally locate the AHU in a part of the building that is outside the isolation shell, such as in the drop ceiling area over a lobby, store room, office, bathroom, etc. It cannot go inside the isolation shell, for the above reasons.

and also I'd like to pitch the ceiling in places to take the height down and not to be parallel to the floor.

Once again, why? For what reason do you want to angle your ceiling? There is no reason to do that, acoustically speaking (myth again) unless you are doing an RFZ-style room design. It just complicates construction considerably, increases costs, and wastes space. You can lower part of the inner-leaf ceiling to accommodate your HVAC ducts and silencer boxes (which are very large), but just do that as a soffit. There's no need to complicate your life by angling your ceiling.

I'm going to use the same GenieClip system again with the ceiling I think.

Once again: you don't need that. Your inner-leaf ceiling will be fully decoupled form the outer leaf, since it will rest only on the inner-leaf walls, so there's no need for clips.

What would be the best way to go about this? Can I build the ceiling INSIDE the room-in-room walls,

Build your inner-leaf walls, then build your inner-leaf ceiling on top of that. There are several possible techniques for doing that, but I prefer to joist run suitably sized joists across the tops of the walls, and either hang the ceiling drywall below that, or put it on top of that for greater ceiling height (= greater room volume = better acoustics). Many of the studios I design, I use a modular ceiling concept that I developed, where you build the ceiling as a series of "inside out" modules that you raise into place. you build them on the floor, then lift them into place between the oversize joists, and seal them in. It maximizes room volume while not complicating the build too much.

Is there a way to safely build a ceiling on top of (and supported entirely by) the stud walls so it doesn't touch the roof at all?

Yep! See above...

How do you make a structure like that safe from collapsing if it is freestanding?

Look at your own pictures that you just posted: How did you make that structure safe from collapsing? After all, it is freestanding?

By the same token, how come your house has not fallen down? That too is free-standing...

Answer: you build it normally, after designing it to be a free sanding structure, taking into account the loads and stresses, and compensating for those in the design. You use things like OSB for sheer strength in the walls, and you dimension the studs and joists according to the loads they must carry. Exactly the same as happened with the design of your house, and the design of the shell you already added on to it. You design it following the principles of engineering that keep all freestanding buildings standing up without falling over or collapsing. The wall framework carries the vertical loads, and the "skin" (sheathing) carries the sheer loads, for the ceiling, the joists carry the vertical loads and transfer them to the walls, which in turn transfer them to the slab, which in turn transfers them to the ground. Lateral loads (sheer) are handled by the sheathing, which is why I normally use one layer of OSB on the studs for both structural and mass purposes, then one or more layer(s) of drywall over that to build up additional mass, as needed. Kills two birds with one stone, so to speak.

Forgot to add the pictures - see below

It looks pretty good, so far!

- Stuart -