Studio at the end of the garden

[Creative24seven]

I'm converting an outbuilding with brick external walls into a studio. It’s a cool old building but I’m slightly contracted by Victorian Architecture. I think we’ve got a plan together but a few things are still confusing me, Can anyone help with these brainaches?


1) Basically, I wanted to do a room inside a room but unfortunately i don't have the height to put in new ceiling joists resting on the new studs. So from what I can tell, I'm left with just decoupling the ceiling as best as possible with Clips and furring Channels. Question is, should I attach the new studs (via the top plates) to the existing ceiling joists or will that defeat the decoupling process completely? Could I maybe use another furring channel running parallel to the new joist (between the stud and ceiling joists) to attach it to the ceiling? Would that help?

Is there any benefit in also using clips and furring channel on the wall to decouple the drywall from the stud? I know the wall’s already de-coupled as such but maybe not to enough of an extent if it’s contact to the building at the top? (The floor is a concrete slab btw so from what I've read the bottom of the stud isn't such an issue.

2) The plan for the new internal walls is - Air gap from brick wall (9" Solid wall) / Wooden Stud / Insulation / Vapour Barrier / Drywall / GG / Drywall. From what i've read Green Glue is the better alternative to say Techsound or similar MLV? Is that a fair assumption? I’m not good with test data etc…


Thanks in advance!

[Soundman2020]

Hi there "Creative24seven", and Welcome!!

but unfortunately i don't have the height to put in new ceiling joists resting on the new studs.

How much height do you have? Without knowing the dimensions of the room, or the purpose, it's hard to give you good advice!

I'm left with just decoupling the ceiling as best as possible with Clips and furring Channels.

How much isolation do you need? Clips and channel MIGHT give you enough isolation... or it might not. It's important to start your studio design by first deciding how many decibels of isolation you need. Then based on that, you can look at methods and materials that will get that much.

should I attach the new studs (via the top plates) to the existing ceiling joists or will that defeat the decoupling process completely?

Yes, that will indeed greatly reduce your isolation. If you don't have a ceiling frame providing the structural integrity for your wall tops, then you will need isolated sway braces at the wall tops to provide that support without damaging your isolation too much.

Could I maybe use another furring channel running parallel to the new joist (between the stud and ceiling joists) to attach it to the ceiling? Would that help?

Not really, no. A solid connection is a solid connection: It doesn't matter much which direction it runs, it will still flank.

Is there any benefit in also using clips and furring channel on the wall to decouple the drywall from the stud?

Once again, without knowing what your goals are in terms of isolation, it's hard to say if that will be "enough", or not. "Enough" for what purpose?

From what i've read Green Glue is the better alternative to say Techsound or similar MLV? Is that a fair assumption? I’m not good with test data etc…

Green Glue and MLV are entirely different products, for different purposes, and they work on different acoustic principles. You might of might not need Green Glue, but it's VERY unlikely that you'll need MLV. MLV does have some uses in acoustics, but not many, and isolating walls isn't one of them. It works for that, yes, but it's extremely expensive. There are far cheaper ways of isolating.

If you provide more info about your studio plans, the current building, the design, your goals, along with diagrams and photos, we'd be able to help you better.


- Stuart -

[Creative24seven]

thanks for taking the time to reply Stuart.

There’s 2.4m between floor and bottom of current joists. I had originally thought of putting new joists next to current ones but say 1” lower but there’s a lot of pipes etc in there so don’t think that would work.

I'm left with just decoupling the ceiling as best as possible with Clips and furring Channels.

How much isolation do you need? Clips and channel MIGHT give you enough isolation... or it might not. It's important to start your studio design by first deciding how many decibels of isolation you need. Then based on that, you can look at methods and materials that will get that much.

This is quite hard to quantify without just saying ‘as much as possible’. I don’t monitor loudly and rarely record anything more than guitar vocal or strings but ould be nice to not worry about turning up occasionally. I have neighbours close by so don’t want to disturb them or be disturbed.

should I attach the new studs (via the top plates) to the existing ceiling joists or will that defeat the decoupling process completely?

Yes, that will indeed greatly reduce your isolation. If you don't have a ceiling frame providing the structural integrity for your wall tops, then you will need isolated sway braces at the wall tops to provide that support without damaging your isolation too much.

A hard connection to the joists does sound like a bad idea.

Could I maybe use another furring channel running parallel to the new joist (between the stud and ceiling joists) to attach it to the ceiling? Would that help?

Not really, no. A solid connection is a solid connection: It doesn't matter much which direction it runs, it will still flank.

If I screw the top of the stud wall to a resilient channel which is isolated via rubber (genie clip and channel) then am I making a hard connection? The drywall is being connected to the ceiling in this way so I thought this might be a good wall of stabilising the stud. I saw in rod gervais’ book, he had suggested connecting a top plate to an rc2 channel. (Figure 12.10?)

Is there any benefit in also using clips and furring channel on the wall to decouple the drywall from the stud?

Once again, without knowing what your goals are in terms of isolation, it's hard to say if that will be "enough", or not. "Enough" for what purpose?

If I can work out a way of avoiding a hard connection of stud to structure then from what I gather, this would probably be un-necessary.

From what i've read Green Glue is the better alternative to say Techsound or similar MLV? Is that a fair assumption? I’m not good with test data etc…

Green Glue and MLV are entirely different products, for different purposes, and they work on different acoustic principles. You might of might not need Green Glue, but it's VERY unlikely that you'll need MLV. MLV does have some uses in acoustics, but not many, and isolating walls isn't one of them. It works for that, yes, but it's extremely expensive. There are far cheaper ways of isolating.

I have limited space where wall thickness is concerned so just want to make sure I’m being as effective as possible within the little room I have. In a system with two layers of board on the inside face of the wall ( which is all I have space for - constrained by fitting a door way to stairs) and something sandwiched in between I was just wondering whether gg or MLV would be more effective. Presume going for one of those options would be more effective than not using either? I think Rod gervais suggested that two layers of board with green glue in between had a similar effect to four layers of drywall.

Thanks. Chris.

[Soundman2020]

There’s 2.4m between floor and bottom of current joists. I had originally thought of putting new joists next to current ones but say 1” lower but there’s a lot of pipes etc in there so don’t think that would work.

You should probably consider doing an "inside out" ceiling: where the drywall goes on top of the new joists, not under them. That maximizes the acoustic height of the ceiling. It's a commonly used technique for small rooms.

This is quite hard to quantify without just saying ‘as much as possible’.

It's actually not that hard to do: All you need is a simple hand-held sound level meter, and a method for making noise.... such as a pair of studio monitors, which I assume you already have. Set up the speakers inside the location where you plan to have the studio, play typical bass-heavy music at a level of around 100 dBC inside the room (wear ear protection), then go measure at several points outside the building, with your meter set to "C" weighting and "slow" response. Make careful notes of where you make each measurement, and note down the actual reading you saw on the meter. Then go turn off the music and take new measurements at each of those same locations, to get just the ambient sound level of your neighborhood. Then take a third set of readings ar a really quiet time of day, when there's no traffic and no noise: maybe 3:00 AM or something like that. That's all the information you need. Now you know how loud you are, how much isolation you are getting at present, and how quiet you have to be. Do the math, and you'll figure out how much isolation you need!

The problem with ‘as much as possible’ is that it isn't a number! There are equations and tables and graphs and charts that deal with isolation, and show you what type of construction you need to build to get specific levels, but all of those reference real decibel levels. There's no way to plug in ‘as much as possible’ to an equation! If you really do wand as much acoustic isolation as it is physically possible to achieve, then that would be something like Galaxy Studios got, which is a little over 100 dB of isolation. That's arguably the best there is. It took them five years to build that, and it cost millions of dollars, as well as requiring the work of one of the worlds leading acousticians, to do things that had not really been done before.... But I'm guessing that isn't really what you mean by ‘as much as possible’....

I don’t monitor loudly and rarely record anything more than guitar vocal or strings but ould be nice to not worry about turning up occasionally. I have neighbours close by so don’t want to disturb them or be disturbed.

OK, but that's only going in one direction; what about the other direction? What sounds are there outside that could trash your recording or mixing sessions? Thunder, rain, hail, or wind. Aircraft or helicopters flying over. Sirens from ambulances / police / fire engines. Nearby trains. Cars arriving / leaving / driving past. Dogs barking outside. Lawnmowers. Loud radios/TVs. Also things inside the building itself, such as water running in pipes, fans, pumps and other motors, people walking on floors, doors closing, people talking, vacuum cleaners, washing machine,phones ringing, furnace.... There's hundreds of possible sounds that could destroy a good recording, or just annoy you as you try to concentrate. Isolation is a two-way street: You need to be thinking about sounds going in both directions, and set your goal to deal with the loudest one. The "loudest one" might well be your music going out, but it also might be something out there that you don't want to let in...

If I screw the top of the stud wall to a resilient channel which is isolated via rubber (genie clip and channel) then am I making a hard connection?

That depends on how you do it! All types of resilient mounts, including rubber, foams, springs, and even just air itself, have a a characteristic called a "spring constant". That tells you how "stiff" the spring is, or how "springy" it is, if you prefer to think of it that way. The spring constant is different for every material. The spring constant also defines how that material can be used to isolate. There's only a small range of possible loads you can put on any specific material where it will actual work to isolate. Normally, you can compress the material somewhere in the range 10% to 20% and ti will work fine. But if you compress it too much then it "bottoms out" and does not isolate. Also, if you don't compress it enough then it "tops out" and does not isolate. Think about the suspension system in your car: It works great for normal driving, but if you load up your car full of bags of cement, rocks, and bricks, you'll completely flatten out the suspension, and the ride will be terrible. By the same token, if you put that same load of cement, rocks and bricks, along with your entire car, on top of suspension spring meant for a huge mining transporter truck, it won't be enough to even compress the spring at all!

If the "spring" in your isolation system is not compressed by just the right amount, then it does not isolate, and you wasted a lot of time, money, and effort. Not only that, but it could actually make matters WORSE by being tuned to the WRONG frequency... in which case not only does it fail to isolate, but rather it can actually amplify the sound...

So you have to make sure that you put the right load on any given type of resilient device, including resilient channel and Genie clips. Those are all designed for very specific load conditions, and if you don't load them correctly, the way they were designed, then you don't get isolation, and could indeed end up with amplification. The reason is very simple: the "spring" together with whatever you attach it to, creates a "Mass-Spring" system, or a "Mass-Spring-Mass" system, which is tuned to one specific resonant frequency. At that frequency, the system does not isolate at all, and instead amplifies. So you have to tune it carefully such that the resonant frequency is below the lowest frequency that you want to isolate. In fact, it has to be about one octave lower, or even lower still. If you get it wrong, then the resonant frequency is within the range that you did want to isolate, ... wellll.... let's just say that it will do the opposite of what you hoped for...

The drywall is being connected to the ceiling in this way so I thought this might be a good wall of stabilising the stud.

How would you go about calculating that? You'd need to know the elastic modulus and Young's modulus for the type of rubber used in that device, then work your way through the math to make sure you load it correctly to get the resonant frequency at least 1.414 times lower than the lowest isolation frequency...

without knowing what your goals are in terms of isolation, it's hard to say if that will be "enough", or not. "Enough" for what purpose?

If I can work out a way of avoiding a hard connection of stud to structure then from what I gather, this would probably be un-necessary.

I'm not sure why you don't want to tell us: We really can't do anything at all if you keep all your dimensions, goals and other details under wraps. That's sort of like going to a doctor, asking him to make you better, but then not telling him what your symptoms are!

and something sandwiched in between I was just wondering whether gg or MLV would be more effective.

You are not comparing like to like: What you are saying there is similar to asking: "I was wondering weather a fish is better, or a bicycle." IF you are hungry, then probably a fish is more useful. If you need to go somewhere, then probably the bicycle is more useful. Green Glue and MLV are two different products that do totally different things.

I have limited space where wall thickness is concerned so just want to make sure I’m being as effective as possible within the little room I have.

Then go for high density materials! What matters most for isolation, is mass: how heavy the material is. High density materials put more mass in a thinner material. For example, the density of plywood is about 550 kg/m3, the density of drywall is about 670 kg/m3, the density of MDF is about 750 kg/m3, and he density of fiber-cement board is about 1550 kg/m3. So if you use fiber-cement board, it can be just one third the thickness of plywood, or one half the thickness of drywall, and still have the same surface mass (surface density). If you want to go to extremes, then the density of steel plate is about 7850 kg/m3, and the density of lead sheeting is about 12,500 kg/m3, so for every place where you would have needed two layers of 16mm drywall for a total of 32mm, you could get the same mass with just 3mm of steel or a bit more than 1.5mm of lead. If you need to save space, then use higher density materials to get the same result. On other other hand, if space is not a concern and what you really need is extreme isolation, then use Green Glue or another constrained layer damping compound. Use each product for the purpose that it was designed, and in the manner that makes the most difference. Putting Green Glue between two layers of drywall is a good idea if you need low frequency isolation improvement, but it would be useless to put Green Glue between two layers of lead, or between a layer of MDF and a brick wall, for example. You can only use materials in the manner that makes sense.

I think Rod gervais suggested that two layers of board with green glue in between had a similar effect to four layers of drywall.

Right. But one layer of steel plate 5mm thick beats them all, as does one layer of brick.

Designing the isolation system for a studio is all about understanding the theory, setting the parameters correctly, then choosing the materials and methods that will get you to the goal you want.

- Stuart -