Stand alone “room in a room” studio build ORANGE NSW Australia

#16

definitely use the box around the column approach in all the rooms. as a note: the air gap between the mass layers is what matters, not the frame. for example: a 2 wall MAM system with drywall on both sides on a 2x6 frame with a 1" (25mm) air gap between the frames, is 11" (or 275mm), so don't move the frames out 200mm, move the frames 25mm and leverage the built in air gap within the frames. same goes for boxing the columns - you only need to be 25mm from the columns. and make sure the columns are full damped because you want them dead for resonances.

so - 2x6 walls between columns. exterior mass plus optional inter-joist mass. 25mm air gap to interior frame. 2x6 frame interior wall with mass on the inside. don't worry about the box inset on the column in the CR. that will be corrected with the acoustic treatment overlays.

#17

Thanks Glenn
I'll spend my time chasing other rabbits down other holes

I'll mock up a closeup sketchup drawing later to confirm I haven't missed anything and tweak my box insets around the live room as well
Andrew

#18

Glenn
I mocked up some shots - just to be sure I'd got it right
Let me know if I failed
Andrew

#19

are you building inside out for the inner room deliberately? if not, the mass goes on the inside of the inner room walls, and its preferable on the outside of the exterior walls. the frames are then separated by 25mm. if you need to separate from the columns on the exterior wall - use 10mm neoprene (or air gap) between wall frame and column, and air gap the column and exterior mass, and use decoupled sway bracing, to stabilize to column. probably will want to use decoupled sway brace (Mason Industries, Kinetics Noise) between exterior and interior wall frames if seismic or heavy winds regulations apply.

#20

Hi Glenn

Thanks for the mock ups

Your design is more space efficient - I'd hit the inside of the room 2*48mm = 96mm from the inside face of the column

The thing for me is that I'm committed to;
1. 2 x 4 frames...not that this would cause issues with what you have drawn - the gap between the frames would just be wider
2. More critically, my cladding will be screwed to the outside of the outer timber frame so my first isolation leaf has to sit on the inside of that timber frame. This timber frame itself also has to sit on the outside of the column - as that lines up with the beams above.

But your design got me thinking - and I turned it upside down - making the outer leaf the one that goes around the column. I'm doing this by adding further timber columns to the frame where it passes the column. I'm not sure this actually works but let me know what you think - mock ups attached.

and just for clarity - here's what the outside wall looks like

Andrew

#21

... except that now you have a three-leaf system...

The sheathing on the outer face of the outer leaf, is now a third leaf. There is the potential to LOSE isolation in the low end due to this problem... You would need to do the math to figure out if this would be a problem for you: determine what the two resonant frequencies would be (f+ and f-), and compare those to the frequencies you need to isolate. Also calculate the isolation you would be getting, and compare that to your isolation goal.

I try to avoid 3-leaf systems as much as possible, and only use them when I don't have a choice. And when that happens, then I design the wall to minimize the problem: Double the mass on the MIDDLE leaf, and keep the two cavities the same size. Any other arrangement is non-optimal.

- Stuart -

#22

not sure why you can't put the exterior mass on the, er, exterior? there are plenty of weather resistant products for this purpose - we use something called "hardie board" in Florida which is essentially concrete fiber board which would meet the mass in fewer (perhaps 1) layer and does a good job with moisture, fire, and hurricanes... that would eliminate any risk of the third leaf loss of isolation and simplify the construction (esp the labor), and likely some of the materials (framing etc - if considering wood - it's likely a good thing).

#23

I totally agree with Glenn: Put the outer leaf mass on the outer face of the building, and gain back the space inside the room. Building the inner leaf around the support columns is the way to go. You gain back quite a bit of room volume and floor area like that, both of which are gold in small studios. And doing the inner-leaf "inside out" is an extra bonus for space, especially for the ceiling.

By the way, how much isolation are you aiming for? I mean in terms of decibels: How many dB do you want for your TL? Based on your designs so far, it seems you need very high isolation, but what is the actual number?

One other thing: When you have multiple layers of drywall to build up the mass, I prefer to make the first layer (on the studs) MDF or structural plywood, for two main reasons: sheer strength, and nailing surface. The wood is much stronger in sheer than drywall (sheer refers the forces acting along the plane of the wall, trying to collapse it sideways). Drywall has almost no sheer strength: it is brittle and fragile. Both MDF and plywood have very good sheer strength. And the "nailing surface" bonus refers to the fact that, if you only have drywall as your sheathing, then you have to go hunting for the studs to attach anything to the wall, which isn't easy if you have 3 layers of drywall between you and the studs! If your base layer is wood, then you can attach things pretty much anywhere, knowing that your nails or screws are always going to hit a solid surface that can hold the fastener and support some weight. This is also a good thing for careless workmanship: A nail or screw through drywall that misses the stud, is basically a potential hole through the sheathing into the cavity. But if there is MDF or plywood behind, then stray fasteners go into something solid at least.

So I'd suggest replacing the first layer with thick MDF or plywood (whichever is cheaper where you live), then putting your final two layers of drywall on top of that. And always stagger the joints! So that the joints between sheets on the second layer do not line up with joints in the first layer. Ditto for the third layer.

- Stuart -

#24

Greetings Andrew,

And always stagger the joints! So that the joints between sheets on the second layer do not line up with joints in the first layer. Ditto for the third layer.

If building codes allow, you can alternate layers with vertical and horizontal mounting of the drywall. This guarantees staggered joints (if not a trip to the orthopedist). Here in the US, horizontal mounting of drywall is usually only allowed in non-commercial construction in many areas.

All the best,

Paul

#25

Soundman2020 wrote:Source of the postBoth MDF and plywood have very good sheer strength.

I would add OSB to that list as its shear strength is very good, too.

#26

Starlight wrote:Source of the post I would add OSB to that list as its shear strength is very good, too.

Yes! I knew I was forgetting something. OSB is better than MDF in that sense.

- Stuart -

#27

Loving this forum and the preparedness of people to spend time, share knowledge and challenge thinking. I really appreciate the time and effort you guys bring.

Looking at your replies it dawned on me how easily you can make decisions in the past which become "fixed" when considering alternatives when circumstances change – I can see that this is what I've done with the outer wall.

Stuart
Re isolation requirements, it might have been a good idea on my part to re-state my objectives at this point where I was drilling down on wall alternatives :oops:

.

Isolation wise, I expect inside measurements up to 115dB. My nearest neighbour’s house is 25-30m from my building and I’d like to be at 40dB by the time I hit his back wall. My inside measurements are based off my own band (drums, bass, guitars and vocals) using my omni and REW software in the garage of my previous home.

Using 4db per doubling of distance, after 16m I will have peeled off another 16dB – so I need my isolation to hit 59dB @ 1m (115-40-16) – make it 60dB. I’m aiming for 70dB and expecting something to upset the applecart.

On the 3 leaf comment – my sketchup shot may have confused matters – the current external cladding looks solid in the shot but it is actually galvanized iron per the pic

which I can’t seem to draw in sketchup – at less than 0.5mm thick and with air flowing freely behind it I’d been told to ignore it as a leaf. Was it that part that led your comment?

I appreciate the advice on the use of ply and/or OSB (thanks Starlight). I ignored it for simplification purposes in my posts (just showing gyprock) but my engineer has specified periodic ply bracing on the first layer.

Glenn
I’m keen to follow this “mass on the outside” approach through – this current focus started from me wanting to get rid of wasted space - so I’m all ears.

I know Hardie products well – they originally came out of Australia. At one stage I was considering using their cement board as my cladding - and am now doing so again :lol:

. I spent some time today measuring things up and mapping out how this could work. The challenge will lie, not in moving mass to the outside per se but in maintaining continuity of mass between the wall and how my damp proofing works. The only way to explain that clearly will be through drawings and some pics. I’ll mock this up as soon as I can.

Andrew

#28

no worries. i think you'll find creating the vapour barriers and moisture barriers as easy as before, perhaps even easier :-)

on the isolation, with the 2x4 replacing the 2x6 (although if you're building a ceiling on the interior walls - best to leave them at 2x6 unless your span and weight calculations indicate a 2x4 wall will suffice), the air gap between mass layers in my example will still be 75mm more than before even with the saving in floor space... as a note, on the mass layer inside, spanning the column area, you'd actually use ladder bridging between the frames inset to the depth of the main drywall layers so you don't extend much beyond the spanning drywall. the goal there is minimize surface disruptions in the control room and this will help with building in the acoustic treatments where symmetry will be critical.

#29

SoWhat wrote:Source of the post Greetings Andrew,

And always stagger the joints! So that the joints between sheets on the second layer do not line up with joints in the first layer. Ditto for the third layer.

If building codes allow, you can alternate layers with vertical and horizontal mounting of the drywall. This guarantees staggered joints (if not a trip to the orthopedist). Here in the US, horizontal mounting of drywall is usually only allowed in non-commercial construction in many areas.

Thanks for chipping in Paul
At one stage I was showing staggered joins and corners in my sketchup drawings but started leaving out that detail when I was changing things around and trying to punch out drawings quickly.
It is my intention to stagger the joins on corners and do the alternating vertical - horizontal hanging. Interestingly in Oz the manufacturer recommends a vertical layer 1 - vertical layer 2 (staggered by a stud width) and horizontal inside - for a 3 layered structure. Based on Stuart's advice I'll only now be using 2 layers of the drywall/gyprock with another of MDF/OSB/Ply so it will be layer 1 - MDF/OSB/Ply - layer 2 and 3 - gyprock.
Andrew

#30

OK – so I’ve played around with drawings and taken some pics and measurements. My wife keeps asking me why I keep standing at looking at the structure rather than working! :lol:

To follow through the “mass on the outside” approach, I took Glenn’s diagram and made some modifications.

: Mass outside - components

: Mass outside - from above

The first modification is to move the outer frame outside the mullion column we’ve been focusing on rather than butting up against it – the reason for that becomes clear when I include the column at the end of the wall – the frame needs to butt up against the end wall column to allow the cladding to sit in front of the column in the corner. I’d lost track of this in focusing on just the isolation around the mullion column. :oops:

The second modification is to put part of the mass on the outside of the frame (1 layer of hardie board – 8.5mm and one layer of 9mm ply) but the rest is in the gaps between the framing (2 x 13mm drywall/gyprock) – I’ve seen this done on a couple of other builds. The reason for only part of the mass sitting outside the frame is to keep the cladding inside the edge of the roof line.
The inner wall is per Glenn’s diagram – noting that I’ve included a layer of mdf/ply/OSB to replace one layer of drywall.

Unless I’ve misinterpreted something – it all hangs together EXCEPT for the weak point at the base.

: Weak point

The damp course and weatherproofing has not been designed or implemented to the strict standards for isolation because I thought my isolation would begin from inside the outer frame.
You can see in this pic below that there is air space between the base plate and the DPC – the 10mm packer sizes it at this point - there are other packers but they are in the shadow under the timber.

: Gap between DSP and Base plate

: DSP fixing inside FYI

This is due to variability in the slab. This means that for the majority of the perimeter the only surface between the outside world and the inside of the outer wall is 0.3mm of aluminium – the DPC. (What I was going to do in my original design was to lay down some extra base plates inside the current one with a DPC and plenty of caulk underneath. The outer leaf was to sit on this. The bottom 90 x 45 would be planed to get close to the slab profile so that the gap underneath stayed manageable for the caulking/sealant underneath and the top would be level.)

So – how to solve the weak point?

Each of these options relies on my calculations that the surface density of treated pine when measured through the 90mm dimension is equal to or greater that my 3 layered wall.

Option 1. Remove all the nails holding the DPC to the base plate and lift the base plate off. Remove the packers. Cut a piece of 90mm treated pine so that it sits under the base plate (call it the fill), caulk heavily the contact between the DPC and the fill, then drop the fill and base plate back on to the dynabolts and re-tighten. Then re-attach the DPC with nails on the inside. I then have continuous mass from slab to the leaves - albeit with the DPC and zincalume sill as part of that.

Option 2. Use the solution I was going to use in my original design (image below) - lay down some extra base plates inside the existing base plate with a DPC underneath and plenty of caulk.

: Option 2

The bottom 90 x 45 would be planed to get close to the slab profile so that the gap stayed manageable for the caulking/sealant underneath and the top would be level. The question is whether this placement of mass has continuity with the rest of the mass - I'd have thought it does through the base plate of the frame.

Option 3. Move to a hybrid structure depicted below where I bring the outer wall inside the frame and have it sit on the 2 layers of 90 x45 as described in Option 2 above.

: Hybrid - option #3

This gets me a continuous mass; brings me to the same position in the room as Glenn’s design; and gives me an air gap of 200mm – my target. I have included a shot of the cladding rather than try to do it in sketchup - while it could be considered a third leaf is has very low mass (.42mm thick) and air flows freely behind it

QUESTION: - which is the best option - or is there something better?

Thanks in advance – I know this post is long and I’m chewing up people’s time here but it’s appreciated – I also live in hope that the exchanges might be of value to others

Andrew

Soundman2020 - Studio Design Forum