Hi again, Lucie. OK, I have a bit more time now, so here goes:
I have Leigh's plans but I was hoping I could post them up here to check we're on the right path and to ask a few questions about the materials and where best to source them if that's ok?
Sure it's OK! That's what the forum is all about!
:)
It's not the biggest studio space compared to those I've seen on here, just 20' x 12' (external measurement) but it's solidly built with the thickest width of timbre the company could supply (44mm).
That's pretty thick, and should make a decent outer-leaf for the isolation. I don't know how much research you've done so far, but the basic plan for heavy isolating (which is what you need for drums) is to build a "room inside a room", which means pretty much what it says: There need to be two sets of surfaces around the studio (called "leaves" in technical parlance), with a gap between them. So your existing solid wood building will be your "outer leaf", then you only need to build the "inner leaf" to complete the isolation shell. The inner leaf is normally built with stud framing and drywall on only one side of the framing, and some form of fibrous insulation in the gap between the two.
The AMOUNT of isolation you will get depends basically on two things: how much mass you have in each leaf, and how big the gap is between them. In other words, heavy, thick, dense materials are better at isolating than thin light-weight materials, and a big gap is better than a small gap.
Leigh's plans already show this type of construction, so clearly he did some good research on this already. But there are also some things on his plans that are not needed, so I'll go over those for you, and try to explain why, and there are also some misconceptions in his notes.
Firstly, take a look at the sixth image you posted, showing the detail of the wall and floor construction. There are several errors here. Firstly, you do not need the resilient bar. The purpose of resilient bar is to decouple the drywall (I think you call it "plasterboard" in the UK) from the studs for people who are NOT building a second stud frame. For example, if you had a wall with drywall on both sides, you could take off the drywall from one side, but resilient bars across the studs, and put the drywall back on again: The drywall is now "decoupled" from the studs, meaning that any vibration in the drywall will be absorbed by the resilient bar, and will not get through to the drywall on the other side. In your case, you are already decoupling the entire wall by building a separate frame, so you don't need to decouple it again with resilient bar. decoupling twice is unnecessary, gains you nothing, and wastes both money and space (not to mention time). So you can leave that out, and save yourself some money there.
Next, there's a not on that same diagram that says "Fix layer 1 to the resilient bar. Fix layers 2 and 3 with Green Glue". There's a major misunderstanding there: You cannot fix drywall with Green Glue, because it isn't really glue at all! That's just a nifty trade name for the product, but it is NOT meant to be adhesive, and cannot be used to stick layers of drywall together. That would be dangerous: sooner or later the drywall would come "unstuck" and fall off, possibly injuring someone.
Green Glue is an acoustic damping product that goes between the layers of drywall to increase isolation. Technically, it is a visco-elastic polymer, which means that it never dries hard and stays soft and rubbery forever. It works as "constrained layer damping", which is a fancy term that means it helps to improve isolation for some types of sound. So yes, it is useful and you can use it, but no, do NOT true to use it as glue! That's not what it is for (despite the name). So you still need to attach each layer as it goes up, with nails, directly into the studs (no resilient channel). You'll need progressively longer nails for each additional layer, as the nails need to penetrate deeply into the studs, so take that into account. The first layer can use normal drywall nails, but they need to be 15mm longer for the second layer, and another 15mm longer than that for the third layer.
Next, same diagram: There's a note there saying that Leigh planned to use different thicknesses of drywall, a "sandwich" of 19mm, 15mm and 12mm layers. That's a myth. Some places on the internet talk about how you can use different thicknesses and different materials to improve internal refraction inside the wall, and change the angles, speeds and other things of the sound waves as they go through the wall, thus increasing isolation. While there is some truth to this, the simple fact remains that "mass rules". Mass is more important. The effect you get from these sandwiches of materials is not very large, and it's better to simply make all three layers as thick as possible, thus increasing the total mass, and really improving the isolation. And if you are already using Green Glue in there, then you already have this effect from the Green Glue itself, so there would be very little additional benefit (if any) from making the middle layer of drywall thinner. Don't do that: just use three layers of 15mm drywall, or if you have the budget (and plenty of strong workers!) then go with 3 layers of 19mm. But that's probably overkill for what you need anyway. Three layers of 15mm is already more than you need, plenty massive, and will give you serious isolation, if done right.
Leigh also asks some questions on that same diagram: One is about the density of the mineral wool insulation that goes in the wall cavity. The answer is: roughly 50 kg/m3. Do not use mineral wool that is very much denser or very much lighter than this. This is the optimal density for best isolation. So try to find something that has density close to this, and you'll be fine. However, if you decide to switch to fiberglass insulation instead, then the optimal density for that is about 30 kg/m3. Each type of insulation has its own characteristics, so be careful with substituting.
Another question is about the depth of the gap between the inner and outer leaf: At least 10 cm, never less, and more if you can afford to lose the space in the room. HOWEVER! There's another misconception evident on that diagram: the term "air gap" refers to the total distance between the existing timber wall and the first layer of plasterboard (drywall) that you put on the studs. In other words, it
includes the insulation! When you think about it, insulation is mostly air anyway, so putting insulation in the cavity does not take out air gap: the air gap is the entire depth of the cavity, regardless of whether or not it is filled with insulation.
So, assuming that you will use 40x90 mm studs (also called "2x4's" generally), to get that 10cm air gap, then you'd only need to leave a space of about 10mm between the studs and the existing wall, since the studs themselves provide 90mm of depth. You can leave MORE space if you want, and that will certainly help with isolation, but to get the minimum 10cm gap, you only need a 1 cm distance between the timber wall and the stud frame.
It looks like Leigh was expecting to leave a larger gap, perhaps aiming for greater isolation, so you can leave whatever size gap you feel will still leave you with a decent amount of space in the finished room. Maybe a total air gap depth of 15cm would be good, which means that you'd need to leave 6cm between the wall and the stud frame.
Leigh also asks about how much mineral wool he needs to put in the cavity: He mentions 75mm, and that's OK, but here it's a case of "more is better". If your budget permits, then you could fill almost the entire cavity with mineral wool, and once again that will improve the total isolation.
Still on the same diagram, there's a light blue rectangle under the layers or drywall, marked "Isolating strip: size? make?". The normal way of doing that is simply with the same type of acoustic sealant that you'll be using by the truckload anyway: As your workers put up each layer of drywall, tell them to place a thin shim on the floor to support the drywall while they nail it, then once it is nailed take out the shim and fill the gap with a piece of backer rod and a bead of acoustic sealant. Repeat the same procedure for each layer of drywall, so you will have a total of size seals under there: one piece of backer rod and one bead of sealant for each sheet of drywall.
(If you can't get good acoustic sealant, then you can substitute a good quality bathroom caulk, but get one that stays flexible and rubbery, and never goes hard!)
(If you can't get backer rod, then don't worry about it too much: just use the sealant or caulk.)
On the same diagram, the floor design is a totally different issue that needs addressing, since what he has there is not a good plan, but I'm running out of time again tonight, so I'll go into that in another post tomorrow.
OK, on to your specific questions:
1. Is 3" x 2" wood ok for the stud walls?
Probably not. I'd go with 2x4's, which are probably 40x90 in the UK, I think. The reason here is that this is a HUGE amount of mass that you'll be putting on those studs. Each square meter of your walls will weigh about 40 kilograms, so the studs need to be pretty sturdy to take that heavy load. You also need to get a structural engineer in to check the floor system of that shed, and make sure that it can take the load! We are talking about putting a load of thousands of kilograms in there, so this is important. Only a qualified engineer can tell you if the building you have can take the load.
2. If we use 3" x 2" wood that means we'd be looking at 75mm thick Rockwool Slabs. Is that thick enough?
Actually, that isn't correct! Wood doesn't really measure what it says it does. This is confusing, but 2x4 studs are not really 2 inches by 4 inches at all! In reality they are only 1-1/2" x 3-1/2". So you can't get 75mm of rockwool into a stud space built with 2x3's, since the actual depth is not 3 inches: it is only 2-1/2", which is just 63.5mm! This is very confusing, but it's related to the way wood contracts when it dries. They really do cut them as 2" by 4" at the sawmill, but as the wood dries, it loses a lot of water, and shrinks down to a smaller size.
But anyway, I'd go with 2x4's for the wall studs, and at least that for the ceiling joists, maybe even larger.
3. There seem to be several different sizes and densities of Rockwool Slab, which one should we go for and what supplier would people in the UK recommend (as I know we'll be needing quite a lot of both the wood and the Rockwool Slabs, I'm worried in case I order the wrong thing!)?
Not sure about suppliers in the UK, but density of around 50kg/m3 is what you need, give or take a bit. Rockwool is a trade name for a specific brand. The generic term is "mineral wool".
4. What width should the air gap be between the stud wall and the shed wall (ideally we need the smallest size possible as space is a bit of an issue)?
Also covered above: the air gap should be 4 inches or 10 cm minimum. The term refers to the distance across the complete cavity, from surface to surface, including the insulation fill (Rockwool), and NOT just the unfilled part. So if you use three layers of 15mm drywall on 2x4 studs, then the total amount of space taken up by that wall will be: 90mm for the studs, 10mm for the extra gap (to get a total of 100mm), and 45mm for the drywall (3 x 15) = 145mm, or roughly 6 inches. There will be at least 75mm of Rockwool in that cavity, and hopefully all 100mm will be filled. Just make sure that you do not over-fill the cavity: Don't force it in! Put in just enough to fill it comfortably, without pushing and shoving or compressing it to make it fit.
5. Aside from the 3 layers of plasterboard fixed onto the inside of the stud wall, should we put another layer of plasterboard on the side of the stud wall that faces the air gap?
Not necessary, no, but you can if you want. With 44 mm timber, you already have good mass there. Just make very, very certain that the timber is very well sealed! There can be no gaps at all in that wall. If it looks like there are gaps there, then seal all of them by forcing abundant acoustic sealant deep into the gap. If there are a LOT of gaps, then yes, add the extra layer of drywall, if you can afford it. You could also use OSB or plywood, instead of drywall. And no matter what you use, seal it! Sealing is incredibly important.
if so, how should this be fixed (with resilient bars again?)
definitely not! You should NEVER leave a small air gap, such as you'd get from using resilient bar directly over a wall surface. That would create a really lousy isolation system. Just put the drywall directly up against the timber, use Green Glue in between if you can afford to, and screws it in place exactly as though you were attaching it to studs.
and should "acoustic membrane" be used as well (I'm not entirely sure what acoustic membrane is at this stage or how it's applied but I'm about to look it up! :oops: )
Another myth! Technically, that's called Mass Loaded Vinyl ("MLV"), and is a thick rubbery layer that is very heavy. Yes, it does work to help isolate sound, but it is extremely expensive! Sounds waves don't care how much you pay for your mass; they can't read price tags, and all they do is react to the amount of mass in the wall. So get the cheapest mass that will do the job! There's nothing magical about MLV: It's just mass in a different form. Yes, it is limp mass, and does have some limited uses in acoustics, but it makes no sense to sandwich inside a wall: that's just a huge waste of money. Forget MLV: you don't need it. Just use relatively cheap mass, such as drywall, plywood, OSB and MDF. kg for kg, they are much cheaper than MLV.
6. In the Cut Away design, the plasterboard rests on an "Isolating Strip". What size and make should we get and where would be the best place to buy it from?
Answered above: build that up as you go, with backer rod and acoustic sealant under each layer of drywall. And not just under it! Also above it, where it joins the new ceiling, and where it meets the other new walls.
7. There also seems to be a sizable gap between the plasterboard and the flooring; Leigh mentions using some sort of liquid sealant to fill it; is this right and if so, what should we use?
No, I would not do the floor like that at all. Big waste of money, not good isolation, waste of room height (which you don't have much of!). But no time to go into that tonight: that's a whole book full, all on its own!
8. Vinyl matting is mentioned as needing to be used in making up the flooring (above and below the wooden frame stuffed with Rockwool). If this is right, what should we go for?
same answer as above: That's not the right way to do the floor.
9. As the Top Down diagram shows, Leigh was thinking about partitioning off the Drum/Vocal section from the main area (I know he wanted to create one big booth that could be used for either purpose, as well as for mic'ing up guitar amps. However I do know that at one stage he was considering putting in a further partition to separate the Drum section from the Vocal section as well...this isn't on the diagram though and I don't know if you'd recommend it? To be honest, I'm not sure we'd have the space to do it!). How should we connect this main partition to the main stud wall? Should it be isolated from the main stud wall somehow?
To be very honest, I don't think you have enough space in there to do that. It would be better to just set up the drums in the rear of the one single room, and use gobos to get some limited separation of instruments. There simply isn't enough space for that. I mean, you COULD fit the walls in there, but you'd end up with to very tiny, very lousy sounding rooms, instead of one spacious, decent sounding room. sound needs space, volume, area to sound good. ITU and EBU recommendations are for a minimum room volume of 43 cubic meters. Any less than that, and the acoustic properties start falling off, fast. You can just barely make that with one room in your shed, and in fact you probably won't even reach that, by the time you have all the isolation in place. But if you tried to have two rooms, you'd have less than half of that in each. Waaaaay less.
10. I know Leigh wanted to keep the apex roof if possible. Will it be ok making up more wood frames filled with Rockwool and fixing them onto and between the main roof supports?
Not really. The "room in a room" concept applies to the ceiling as well! In other words, you need to build a new ceiling in the exact same manner as the new walls. That new ceiling must rest ONLY on the new walls, and CANNOT touch any part of the existing structure. It has to be totally separate. That's why the concept is called "room in a room". Rooms have walls and ceilings too! Isolation is an "all or nothing" proposition. All four walls, and the ceiling, have to be done to the same level. Same procedure for the ceiling: 2x4 framing (gabled if you want), with three layers of drywall, sealed and caulked.
11. Leigh was worried about the double doors being a big problem.
They are! And a big problem, too. But as I said, I'm out of time again tonight (and wearing out my keyboard, too!), so I'll cover that another day, along with your floor. But basically our best option here if you want natural light is two sets of sliding glass doors, of the right type, and with thick laminate glass in them. The only trouble with those things is price: They are NOT cheap! They'll do what you want, but you'll blow your entire budget just on those...
I know I'm probably biting off far more than I can chew but if we're on the right track it would be great to know and to get any advice we can on the build before I start ordering materials (which ideally would be good to start doing this week if possible)
Starting this week seems more than just a little optimistic!!!!! You don't even have a workable plan yet: maybe you should re-think that schedule slightly....
:)
I'll be passing on all info to our builder and electrician so, fingers crossed, between us we'll be able to figure it all out.
I'm sure we can figure it out, but there's more to this than Leigh had in his notes, and some major parts are missing. Namely: HVAC. That stands for Heating, Ventilation and Air Conditioning. In order to be fully isolated, the room will be built as two totally sealed air-tight shells. That's the "room in a room" thing again. each "room" is sealed, hermetically. Even the doors will have multiple rubber seals on them. So you MUST have a system for getting fresh air into the room, and getting stale air out of it. That's the "V" part of HVAC. But moving air in and out means that you have to cut holes in your perfect air-tight seals! So clearly there's an issue here: you need isolated ducts, in-line silencers, and very quite fans to move the air through the ducts. It can be done fairly simply, but it's something that isn't even on your list, and is critically important: Leigh won't be able to work in there for very long at all with no air to breathe!
The room will also be surrounded by a very thick layer of thermal insulation, both in the wall cavity and also in the room treatment: so heat ain't goin' nowhere! What's in stays in, and what’s outside stays outside. So you also need a way to cool that place, especially in summer. That's the "AC" part of HVAC. The air conditioner also does something else that is very important: it controls humidity. Hugely important, in fact. Musical instruments, microphones, equipment, and people are all sensitive to humidity. It has to be kept under control. And finally, if you live in a very cold climate, you might even need the "H" part of HVAC: heating. That can probably be handled by the same air conditioning unit: some do both.
You also need to consider how to isolate the electrical system: Your electrician can't simply go around punching holes in your triple-super-sealed-hermetic-acoustic-isolation-walls that cost you a fortune to build, to put in plugs, lights and switches! There can be NO holes! Everything must be surface mounted within the room. No penetrations at all through the wall. That's another key challenge.
So, anyway, the good news is that you are totally on the right basic track with what Leigh has on the diagrams, but with some caveats. Some are small, but some are big. But the other good news is that they can all be fixed.
:)
Hopefully tomorrow I'll be able to add some more, but this should help a bit in the meantime.
- Stuart -