Ground-up studio build in Perth

[Birdsteeth]

Things are finally starting to progress with the basic outside structure pretty much complete now that the floor slab has been poured. The next steps are:
- Rendering the inside of the brickwork
- All of the joists are coming down as they're not being used at all. The builder said the joists and the hangers are fine to come down as they're not structural
- Getting some scaffolding in and caulking all of the seams in the plywood
- After caulking is done, I'll be 'plugging' in between the rafters on the underside of the plywood with 16mm gyprock and GreenGlue to beef up the ceiling, which is my 1st leaf.
- There is a gap where the pitch of the roof passes over the top of the wall plate. My plan is to plug up all of these gaps with wood that is cut along the top edge the same angle as the roof pitch. Of course, after all this 'plugging' is done I'll be caulking every edge and seam to ensure it's all air-tight.
I'm starting to realise what a mammoth job this all is and I have nothing but huge respect for everyone that's done it before me... everyone on this forum must be nuts!! Every time I go down to my build it's like I see $20 notes flying away before my eyes and my $40k fit-out budget gets skinnier and skinnier.. Ah well, at least there's now some solid progress happening.

Sam.

[stevev]

lookin' good there Sam

- Getting some scaffolding in and caulking all of the seams in the plywood

good idea.

After caulking is done, I'll be 'plugging' in between the rafters on the underside of the plywood with 16mm gyprock and GreenGlue to beef up the ceiling, which is my 1st leaf.

another good idea. Out of curiosity, what thickness is the ply on the roof?

There is a gap where the pitch of the roof passes over the top of the wall plate. My plan is to plug up all of these gaps with wood that is cut along the top edge the same angle as the roof pitch. Of course, after all this 'plugging' is done I'll be caulking every edge and seam to ensure it's all air-tight.

and another good idea. By this point you're probably gathering that buying sealant (caulking) by the box full is the way to go what sealant are you using by the way?

I'm starting to realise what a mammoth job this all is and I have nothing but huge respect for everyone that's done it before me... everyone on this forum must be nuts!! Every time I go down to my build it's like I see $20 notes flying away before my eyes and my $40k fit-out budget gets skinnier and skinnier.. Ah well, at least there's now some solid progress happening.

yep, it's a pretty mad undertaking building your own studio, that's for sure. I have a background in construction and I reckon i underestimated the difficulty of my build by about 60%, and budget by about 30%!! That's not meant to put you off, but just to let you know we've all been there I think you'll be pretty close with 40K for fitout....and mate, at the end of it, when you're sitting in the sweet spot of your control room with a big grin on your face....that's when it'll all be well and truly worth it.

[Birdsteeth]

G'day Steve,

I'm just about to order my GreenGlue, I've got about 150 liters of the compound and 2 boxes of the sealant quoted up. The company I'm getting it from, Robert at Foam Sealants, has been helpful in looking at my drawings and suggesting quantities. Although, looking at it now and planning to do the roof seams, I might need more sealant.

The ply in the ceiling is 13mm marine ply... the whole first shipment got stolen from outside our build a couple of months ago; I reckon there was $4000 worth of ply there. We went down this morning and checked the house build and discovered that 3 toilets and 2 hand basins had been lifted from the house as well! The building company pay for it, still it's a major pain in the arse with delays etc plus I hate dishonest scumbags.

My building supervisor has been great and he's allowing me to get in and start work on the room before handover, so the rendering should start next week. I've taken most of November off work to focus solely on the studio for a month, hopefully I'll get a fair chunk of it knocked off by then.

Cheers mate,

Sam.

[stevev]

The company I'm getting it from, Robert at Foam Sealants, has been helpful in looking at my drawings and suggesting quantities. Although, looking at it now and planning to do the roof seams, I might need more sealant.

yep, same place I got mine from and Rob was really helpful. I think I ended up going through 3 boxes plus a couple of extra tubes. I think I originally ordered 2 cases of sealant and shipping for the third case and extras was $30 or $40 so I shoud've over ordered in the first place

We went down this morning and checked the house build and discovered that 3 toilets and 2 hand basins had been lifted from the house as well! The building company pay for it, still it's a major pain in the arse with delays etc plus I hate dishonest scumbags.

gives you the shits doesn't it glad it's not coming out of your pocket though!!

My building supervisor has been great and he's allowing me to get in and start work on the room before handover, so the rendering should start next week. I've taken most of November off work to focus solely on the studio for a month, hopefully I'll get a fair chunk of it knocked off by then.

good on ya'! looking forward to seeing progress as it goes along. Just for a bit of scientific experimentation: have a good listen to the reverb of the space before you start rendering, and then have a listen once you finish. I was actually quite amazed at the difference it made in my build so i'd be interested to see if you have the same experience.

[Birdsteeth]

Rendering has begun! It's rough as guts but I'm not planning on turning pro anytime soon, plus no one's going to see it after the walls go up. I reckon there's another 2 day work just on this, next step is to beef up the bottom of the ply (green glue should be here any day now along with my plasterboard) and plug between the rafters. Once this is all done, we should be in the new house and my framing can start.

On another note, the builders have seriously over ordered insulation. I grabbed about 20 bags of it from the garage before anyone could take it away, I paid for it somewhere along the line I guess. Now to try and hang onto it until I can start the walls, hopefully some prick doesn't lift it!

[stevev]

Rendering has begun! It's rough as guts but I'm not planning on turning pro anytime soon, plus no one's going to see it after the walls go up.

looking good there mate, and reminds me of exactly what my build looked like at this point If there's any holes or gaps, you can run over the top of the render with a damp-ish sponge once it's semi cured, which will seal it right up.

On another note, the builders have seriously over ordered insulation. I grabbed about 20 bags of it from the garage before anyone could take it away, I paid for it somewhere along the line I guess. Now to try and hang onto it until I can start the walls, hopefully some prick doesn't lift it!

you're going to need to figure out what density that insulation is if it's going to be of any use to you acoustically. If it's fibreglass, which it certainly looks like, then it'll need to be around 30kg/ cubic meter to have the right gas flow resistivity for cavity damping. Unfortuantely, from the pics i'm going to peg it as the standard 10-12kg/cubic meter variety. sorry to say, but if it is then it's of no use to you for cavity damping

[Birdsteeth]

Ahh, bugger.. It's R4.1, I can't find any information on the density anywhere. How would I figure that out I wonder?

[stevev]

is there a brand somewhere on the packaging? if so then get in contact with them, if not then i'd say it's not likely to be havier than 10kg/m as you'd stick your name all over it if you were going to the trouble of making heavy fibreglass insulation. Your builder might have some contact details.

The only other way I can think of is the real-world method: weigh one or two of the batts and then break out the calculator to work out your cubic meter. Not as accurate as weighing a full meter of the stuff but it'll probably give you a reasonable enough idea of whether it's usable. A pair of digital kitchen scales would probably do the trick

[Birdsteeth]

Okay, update time!

We moved into the house about a month ago and work has started in earnest on the studio. I have taken 4 weeks off work to try and 'break the back' of the build. First I dropped all the joists the builders put up which I can reuse in the ceiling I'm building. At the moment all my time and effort has been taken up by cutting 16mm gyprock to GreenGlue and screw in between the rafters to beef up the plywood in the roof. It's been slow, crappy work... I was hoping to get it done in a week but it'll probably be two (hopefully).

My air-conditioners have arrived, I got a 5kw and a 3 1/2kw Daikin Ururu system and I have my air-con guy lined up to start as soon as the walls are up. My sister-in-law electrician is booked in tomorrow to come and start running cable with me, so there's definitely progress happening; it's just not real exciting currently. It'll all be worth it though when I get the isolation I'm after.

Sam.

[Birdsteeth]

Oh and Steve, the insulation I've got I was thinking of putting it in the air gap between the brick wall and the gyprock. I seem to remember reading in Rod Gervias' book about just using normal batts for that while I'll get denser Rockwool for the inside-out walls underneath the material. Does that sound right?

[stevev]

Oh and Steve, the insulation I've got I was thinking of putting it in the air gap between the brick wall and the gyprock. I seem to remember reading in Rod Gervias' book about just using normal batts for that while I'll get denser Rockwool for the inside-out walls underneath the material. Does that sound right?

hmmmm, can you point me to where it says that in Rod's book? I haven't read it for quite a while!

As far as isolation goes, you'll definitely want the right weight insulation in the wall cavity. (between the bricks and gyprock). That's the 'spring' in MSM. much like a shock absorber in a vehicle, too light and it bounces all over the place and does nothing, too heavy and you feel every single bump in the road.

I don't fully understand the science behind gas-flow-resistivity, but the numbers add up to insulation weight needing to be 30kg/cubic meter for fibreglass and 50kg/cubic meter for rockwool....give or take...

I used bradford soundscreen at 24kg/m as it was the closest to 30kg/m and the most cost effective. After that the only closest I could find was Flethcher FI32......Cost almost doubled

I used the FI32 for the control room 'acoustic treatment under the fabric' as it's as good as it gets for that purpose in australia (Fletcher FI 48 is also excellent)


Everything is looking great there mate, and your attention to detail is spot on It's some seriously boring work with the gyprock, but we've all been there. You'll grow to love that panel lifter as the build progresses

...and a sister-in-law sparky......WIN keep the progress reports coming.

[Birdsteeth]

Thanks Steve, I've been re-reading Rod's book and I think I must've invented that.. I could've swore I saw that you could just use any insulation Anyway, would this be suitable: http://www.ais-group.com.au/multi-purpose-slab300 These guys are in Perth and I read on another forum that it wasn't too expensive. Sorry for all the insulation questions, I don't know why I'm such an insulation dunce!

[Soundman2020]

Fibrous insulation (such as fiberglass wool, and mineral wool) are porous absorbers, as are open-cell foams, most fabrics, and many other similar materials that are made up of a maze of interconnected pieces of soft, resilient material with air spaces between them, all the way through. The defining characteristic for how a porous absorber behaves acoustically, is something called "gas flow resistivity" or GFR, which has the unlikely units of "mks Rayls/m" or also "kPa*s/m²". Basically, that describes how the material resists the flow of gas as it passes through.

So why is that important?


Two things happen when sound strikes a porous absorber. First, there's a sudden change in impedance as it hits the surface, so part of the wave is reflected back, and part carries on (plus part could be refracted too, and even diffracted, but let's leave those aside for now!). That initial impedance change varies according to the porosity of the material: less porous (lower density) means less impedance, means that the wave is less reflected. Lower porosity (higher density) means that more of the wave is reflected. And since this is impedance, the effect varies with frequency. So some portion of the sound spectrum is reflected right at the surface, and some portion carries on into the material. (To confuse matters even more, this also depends on the angle that the sound strikes the surface...).

GFR doesn't tell you much about the part that bounces back, but it does tell you a lot about the part that didn't.

The part of the sound that is carries on into the absorber, runs into resistance as it moves forward, because there are numerous "barriers" (fibers) in its path. GFR measures this, as the relationship between pressure and flow. In other words: what amount of gas pressure causes what amount of gas flow. Since sound waves are basically made of of air pressure "vibrations", and air is made up of a bunch of gasses, this makes perfect sense. (After all, the way we measure sound intensity is by measuring how much the air pressure changes as sound waves go by, and we do this with an SPL meter: Sound Pressure Meter. The reading on the meter shows dB SPL)

In essence, a sound wave is just gas moving backwards and forwards through the maze of fibers inside the insulation material. Each wave is a pressure change that causes gas to flow, and the GFR number just tells you about how that works inside the material: what amount of sound pressure causes what amount of air to flow, and how that differs from the way it would be if there were no insulation, only air. Bigger numbers mean that the materials resits the flow of gas (= passage of sound) more than smaller numbers.

The actual mechanism here is that some of the air molecules bump into some of the fibers, causing the air molecules to slow down or stop, and causing the fiber to move. So the air molecule transfers some of its energy to the fiber, which bends and flexes, and converts that energy into low grade heat. In other words, the fiber changes sound energy into heat energy. By doing that, it slows down the air movement through the material (since energy was lost). So the pressure that should have caused a certain amount of air to flow if there were no fibers, actually causes less air flow because the fibers take some of the energy away, slowing down the flow. That's what we call "resistivity". The fibers "resist" the flow of air. That's the actual mechanism that makes porous absorbers so useful in acoustics.

But a sound wave isn't just air moving in one direction constantly, like wind blowing: rather, it is "vibrations" of air: the pressure is first higher (pushing air forwards) then lower (sucking it back again). So it is possible that on each forward-backward cycle, any given molecule might not move far enough to hit a fiber before it gets sucked back again, and didn't hit any fibers going that way either: for that molecule, there is no resistivity. But the molecule right next to it might hit a fiber each time it goes forwards, then hit nothing as it gets sucked back. And a third molecule might hit different fibers going each way. The number of molecules that hit fibers, or don't hit fibers, depends on two things: how far the molecules move on average for each cycle (which depends directly on the frequency and intensity of the sound wave), and how far apart the fibers are. We have another word for "how far apart the fibers are". We call that "density". More dense insulation has more fibers per cubic inch, and therefore there will be more molecules hitting fibers, on average. So in general, higher density insulation also has higher Gas Flow Resistivity.

But that's not the end of the story! Different types of fiber behave differently, even for the same number per cubic meter or cubic inch. Think microscopically, and imagine a hypothetical material where there are one thousand fibers in one cubic inch: if all of those one thousand fibers are made of very thick solid heavy steel, the vibrating air molecules will just bounce right off at the same speed (but different direction), since they won't be able to cause the steel to move at all, this transferring no energy. So practically no sound is absorbed by the "fibers" in this case. On the other hand, if those one thousand fibers are all made of light soft flexible bouncy rubber, then the molecules that hit them will slow down a lot, transferring a lot of their energy to the fibers.

There's also the issue of how big each fiber is (diameter), and if they are all the same or not. Some materials have many different sizes of fiber with different properties, while others are very consistent.

So there are many factors that affect how a sound wave is absorbed by any particular type of insulation. The GFR is the number that tells you a lot about that.

Unfortunately, most manufacturers don't bother measuring or publishing the GFR numbers for their insulation products, for a simple reason: GFR is not a useful number for talking about thermal isolation, and those guys sell the vast majority of their products for thermal applications. The fact that the same products also work for acoustic absorption is sort of a luck coincidence, but its just a very small fraction of the total market, so it's not worth it for them to measure and publish GFR data. Some do, but very few.

Fortunately, there is a rough (very rough, and not linear) relationship between the density of each type of material, and its gas flow resistivity. It turns out that for fiberglass insulation, the optimum density for MSM applications is about 30 kg/m3, but in the case of mineral wool insulation, the density needs to be about 50 kg/m3 to get the same results.

Please note that this is optimum for the insulation that you put inside your isolation walls: You might well need different densities for other acoustic applications. Maybe a bit less dense for bass traps, and a bit more dense for high frequency absorption. Thickness also matters, as do several other factors.

It's actually a bit more complicated than the above, but that's a useful way of thinking about how it works. Gives you a good "mental picture" of what is going in inside a porous absorber, at the microscopic level.


- Stuart -

[stevev]

I don't fully understand the science behind gas-flow-resistivity,

yeah, see how I said that. Stuart has well and truly explained the science in a way that makes sense to your average studio builder

Could that explanation please be made into a sticky under the title of 'what insulation should I use for my MSM construction?'.

thanks Stuart.

steve

[stevev]

...and regarding

Anyway, would this be suitable: http://www.ais-group.com.au/multi-purpose-slab300 These guys are in Perth and I read on another forum that it wasn't too expensive.

the info I was able to get didn't state a definte density, just a range between 30-200kg/m. That's pretty broad! If the product you're looking at is rockwool and around 50kg/m3 then great

steve