Garage home studio - walls

Hi I've looked through this forum and find all the comment really useful, although equally scary! I'm a lifelong musician looking to turn most of my garage into a relatively soundproofed room where I can record vocals, guitars, maybe even drums, and also mix. Through reading and asking questions, I feel I have enough knowledge to have a go (with a builder I'm using), but I wanted to clarify one thing. My garage is timber walled on three sides and breeze block on the other. The floor is concrete (to which we're adding more concrete to level it) and my nearest neighbour is 15' away. As per the attached (rough, apologies) diagram, I'm intending to use around 3/4 of my garage space for my studio. I'm planning to build a room with in room using a timber frame, insulating with rock wool, having an air gap, and fixing drywall. My builder is first planning to insulate and drywall the existing garage outer walls and roof (a pavilion style that goes about 12 foot from the ground - see photo). Then make the inner room. Should the inner room consist of a double framed wall - i.e. two separate frames each containing insulation, with a gap between, with two layers of drywall joined with green glue on each outer wall? Or should the inner room have a single frame only, with the two layers of drywall on the inside of this? And fix the double layer of drywall, insulation to the existing garage walls? Hope this make sense. Also - my builder has says he intends to use "Sound Board 'A'" by which I presume he means specialist acoustic board. If I'm having a two-leaf wall system, with two layers of board on inner and outer wall, is it sufficient to use normal drywall rather than acoustic board - as it's a lot cheaper? Appreciate your feedback.

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things! :)

The floor is concrete (to which we're adding more concrete to level it)

Instead of concrete, I'd suggest adding self-leveling cement. It's a lot easier to get a flat, level, smooth surface using a product that is specifically designed to do exactly that.

I'm planning to build a room with in room using a timber frame, insulating with rock wool, having an air gap, and fixing drywall. My builder is first planning to insulate and drywall the existing garage outer walls and roof (a pavilion style that goes about 12 foot from the ground - see photo). Then make the inner room.

You seem to be misunderstanding the concept of "room in a room". More accurately, what you need to do is to create a fully decoupled 2-leaf MSM system. The two leaves are: 1) The "outer leaf", which is your existing garage structure, and 2) The actual "inner leaf", which is a simple wood frame with drywall on ONE side only. That's it. There are no more rooms, walls, frames or anything else involved. Since you plan to use only part of your garage (not the entire thing), then you'll have to build a partition across the garage to section off the part you won't be using, thus completing the "outer-leaf" around the part you will be using. If you add drywall to the existing garage framing and then build your studio, you will have created the dreaded "three-leaf system", which will ALWAYS give you WORSE isolation for the low frequencies than the equivalent 2 leaf would have, all other factors being equal. Never build a 3-leaf wall if you can possibly avoid it, nor a 4-leaf, 5-leaf or any other number of leaves. Only ever build 2-leaf, unless there's some really valid overriding reason to not do that.

Should the inner room consist of a double framed wall - i.e. two separate frames each containing insulation, with a gap between, with two layers of drywall joined with green glue on each outer wall?

No. The inner-leaf is a single stud frame with sheathing on just ONE side of that framing. The sheathing might consist of several layers, if you need high isolation, but they all go on top of each other, on the same single side of the frame.

Or should the inner room have a single frame only, with the two layers of drywall on the inside of this? And fix the double layer of drywall, insulation to the existing garage walls?

Yes to the forst part of that question, no to the second part. The existing stud frame should stay exactly as it is: if you put drywall on those studs, then you will create a 3-leaf system. If you do not have enough mass in your existing outer-leaf, then you might need to "beef it up" by adding drywall up tightly against it, in between the studs, but not ON the studs. When you do the math to figure out the isolation of your wall, then you can decide if you need to do that or not. But if you do need more mass there, then it all has to be in one "bunch", all together, pressed up against the existing sheathing, as one single leaf with no air gaps in between.

Also - my builder has says he intends to use "Sound Board 'A'" by which I presume he means specialist acoustic board. If I'm having a two-leaf wall system, with two layers of board on inner and outer wall, is it sufficient to use normal drywall rather than acoustic board - as it's a lot cheaper?

Think of it this way: sound waves are not snobbish, and can't read price tags anyway, so they really don't care how much you pay for each kilogram of your mass: All they care about, is the mass itself. Price is meaningless to them. The equations for calculating your isolation also have no place to insert the price... :) All the equations use is "mass". Period. End of story. So get the lowest cost mass that will do the job. It's that simple. Yes, there's a lot of companies out there that make wonderful claims about how well their products isolate sound (or even worse, how well they "soundproof"... as if that was even a technical word that acousticians use...), but in reality, there is no product that can beat the laws of physics. There's no magical ingredient that a drywall manufacturer can add to the mix to make his kilograms more effective than anyone else's kilograms: Pixie dust doesn't work, and unicorns seem to be in short supply... so all that we have is mass. be vary wary of claims about products that fly in the face of science. The way walls isolate is well understood, the calculations are simple, and there's only room for three parameters in those equations: how much mass you have in the wall, how deep the air gap is in the wall, and how much "damping" (insulation) you have in the air gap. That's it. It's a simple Mass-Spring-Mass system, where the drywall on each side of the air gap is the two "masses", and the air in between is the "spring", which is damped by the insulation. A very well understood system. In other words, compare the surface density (kilograms per square meter) of the various building products that are available in your area, such as ordinary drywall, fire-rated drywall, MDF, OSB, plywood, fiber-cement board, etc., and see which one has the lowest cost per kg. That's the one you want. - Stuart - - Stuart -

Thanks Stuart. I appreciate your response. (By the way I've updated my profile also :-)) I have amended the diagram (again apologies for its' rough and ready-ness) and would ask the following please. Two of the exterior garage walls are made of featherboard timber (quite thin) on studs. The front is two sets of timber double doors with thicker wooden posts to their sides and centre. I have attempted to show this more accurately, attached. If, as you helpfully suggest, I partition the area of the garage I wish to use for my studio, I imagine I will have to partition in front of one and a half sets of the front double doors as shown also. Would it not be best then to instead extend this partition to make the outer leaf (shown in blue) - i.e. a frame with two layers of drywall on the outside of this with rockwool underneath, then the air gap; followed by the inner leaf (in red) with the same make up but with the drywall on the inner side? (All both walls and ceiling). And leave the current garage exterior walls and doors untouched? I'm not sure I'm following what you suggested... If I just add insulation only flat against the inside of the existing garage walls with no drywall there (the double doors would be an issue as I was aiming to have one of these - shown - as opening) .. and then build a single frame for the inner room with drywall on the inside only, am I NOT then getting the two leafs of drywall & insulation as shown in Rod Gervais's STC 63 diagram? Would it work if I did what I suggested above (aiming for the STC 63 set up with a frame within a frame - my blue and red boxes on my diagram) and left the existing garage structure alone completely? Sorry (again) if I'm unclear or ignorant (or both). I very much appreciate your advice. Thanks John

I'm not sure if those were windows or doors in your drawing for your room in a room, but here's how I would do it. Sorry if I messed anything up. I drew this up as quickly as possible. The pink is insulation. The stuff that looks like OSB is OSB. The white is drywall. The wood looking stuff is wood. And the concrete is concrete. I used a tan color to represent your existing doors. And I didn't draw any sheathing, but this should give you the general idea. Basically, seal off your doors using a ton of mass. Between every layer of material, use Green Glue compound. Seal everything with sealant. The inner leaf is all inside-out except the concrete wall (the one on the bottom of my picture) as I figure it's probably best to leave a gap there for the MSM equation to work as well as to provide space between the outer wall and your vapour barrier. For scale reference, the inner walls are 2x4's. The outer is 2x6 and the wall sealing up/beefing up the garage door is 2x6. I left you dimensions (rough, based off of your initial diagram) to show roughly how big of space you'll have. Not how thin your room is (not even 6 1/2 feet wide!) You really should consider using the entire space as I'm not sure what good 4' of hallway is going to do you. However, acoustically speaking, that 4' will make or break your room! Greg

By the way I've updated my profile also

:thu: Start from the right hand side of your diagram, outside the walls, and move your way inwards, counting the leaves as you go: Breezeblock = leaf #1, blue line " leaf #2, red line = leaf #3. :) The same is true for the doors at the top (which do count as a leaf) and also the wall at the bottom. They are all 3-leaf walls. This is the concept you need to emulate: The outer wall around everything in that image, is equivalent to your garage wall, and is the outer leaf (yours is a bit different, since one side is breeze block and he other three are just siding on studs, but the same idea applies). But since you are only going to use a part of that space, not all of it, you need to partition off that area. You can see the L-shaped isolation wall that was added here to do that, across the far corner, completing the other two sides of the "outer leaf" around that isolated area. Then the single "inner-leaf" was built inside it. This is just to illustrate the concept, of course: you'd need to adapt it to fit your scenario, but the concept is there. In your case, you will need to build the isolation wall sufficiently far away from the double doors that they aren't an issue. In other words, far enough away that the resonant frequency is way below the bottom of the audible spectrum. (Isolation walls are resonant systems, and need to be tuned. The equations for tuning them are very simple). Assume that your doors would be in the bottom right wall of this image, and you'll get the right perspective. Your garage doors, of course, will have to be bolted in place and sealed up. They won't be usable any more. Posting photos of the actual garage, several views, from the inside and the outside, would help us to understand things better. - Stuart -

Thanks Gregwor and Stuart. Much appreciated. Stuart, as requested, I've attached several photos. I lay awake last night thinking about all this. Not sure it helped! In your diagram, am I not getting three layers with the current garage exterior wall, the partition, then the inner room layer? It would really help me if you could describe exactly how each layer should be constructed. As for the ceiling height, because the main horizontal support beams are only 6' from the floor, I intend to build my inner room frame higher than these, with a new flat ceiling say 8' from the floor mounted on the new frame, so that they will be within the inner room. I appreciate this is less than ideal as they will touch the outer layer, but I don't have the budget to do anything else. And my plan is to insulate them and caulk round where they meet the new walls. Thank you so much. John

In your diagram, am I not getting three layers with the current garage exterior wall, the partition, then the inner room layer?

The only spot it would be a three leaf design would be with the existing garage doors. Since you have actual wooden doors, it's possible for you to beef them up, make them rigid and seal the heck out of them. Most other people have think crappy metal garage doors and the way I drew it for you would be how you deal with those.

As for the ceiling height, because the main horizontal support beams are only 6' from the floor, I intend to build my inner room frame higher than these, with a new flat ceiling say 8' from the floor mounted on the new frame, so that they will be within the inner room. I appreciate this is less than ideal as they will touch the outer layer, but I don't have the budget to do anything else. And my plan is to insulate them and caulk round where they meet the new walls.

This is a beautiful building! Sadly, without a major overhaul, I can't see how you're going to make it work as a true room in a room. Maybe Stuart can point you in a better direction, but clips and hat might be your only option :-S Greg

Thanks Gregwor. It is indeed a beautiful building and we're lucky to have it (moved here five months ago). Re the ceiling, I totally appreciate I'm going to end up with a somewhat flawed studio space. But I'm currently trying to make music in a small untreated attic up a ladder! I know this won't be perfect but I do hope it will get me another step along and be a big improvement. (Lord, I hope so given the money we're about to spend on it !) I understand what you're saying about the garage doors. I didn't want to seal them up just in case it's a problem when we come to sell (not for a while given how stressful buying and selling houses is in the UK!). I appreciate your input very much indeed. John

Re the ceiling, I totally appreciate I'm going to end up with a somewhat flawed studio space. But I'm currently trying to make music in a small untreated attic up a ladder! I know this won't be perfect but I do hope it will get me another step along and be a big improvement.

I wouldn't say it's going to be flawed. You're smart enough to have come on the forum before building. If you had built without checking here first, THEN it would have been flawed. Having any space is better than no space. I'd love to see some pictures of the attic space just for fun! The garage will be a huge improvement from your attic space, I'm sure!

(Lord, I hope so given the money we're about to spend on it !)

With some studying and 3D modelling, you'll know exactly how your room will perform BEFORE you start building it. You won't have to hope it works.

I understand what you're saying about the garage doors. I didn't want to seal them up just in case it's a problem when we come to sell (not for a while given how stressful buying and selling houses is in the UK!).

I've been in the middle of a move for a year and a half, so I feel your pain! Having said that, you will have to do some extensive building in your garage, so inevitably it will be a hassle when you sell. Greg

Thanks again Gregwor. I feel your pain re moving ! I've attached a photo of my attic as you were interested :-) Also I have a question regarding the ceiling of my new inner room. Because it's a pavilion roof, and I'm using only part of the garage, when you look longwise down the new room towards my proposed mixing position, the ceiling on the right side will slope to follow the slope of the outer roof. On the left hand side, the builder's plan was to make it 90 degrees. The room will be used for both mixing and recording (not ideal I totally appreciate). But from a mixing perspective I understand that symmetry is good. So I feel I should tell him to slope the ceiling on the right side in the same way as the left. In my very impressive diagram, Option 1 shows the builder's current plan. Option 2 shows what I think will be better. The black lines are the current garage outer boundaries. Blue is a proposed new internal partition wall. Red shows my inner room. The black line that's highlighted yellow will have increased mass so it will be my second (outer) leaf. The partition wall (blue) will be the outer leaf on that side. The ceiling across the width of the new room will be sloped at both ends, following the existing roof slope. I think I'll post this question as a new post as well, but I'd be interested to know what you think. Thanks John

I've attached a photo of my attic as you were interested :-)

That space looks cozy! Just needs some treatment and for you to rip out the rug!!

But from a mixing perspective I understand that symmetry is good. So I feel I should tell him to slope the ceiling on the right side in the same way as the left.

Correct.

Blue is a proposed new internal partition wall.

Other than hanging some shovels or whatever on the hallway that will be left in your garage, what is the purpose of the hallway? I feel like it's such a small space, it's silly to go through the hassle of leaving the hallway. You could have a way better recording space (that is symmetrical) if you use the entire garage for your studio.

Red shows my inner room.

I know it may just be terminology here, but I thought we decided it is basically impossible to effectively build a fully decoupled inner leaf MSM room. Or are you still going to try and design it so it works? Again, I thought you were just going to use clips and hat instead?

The black line that's highlighted yellow will have increased mass so it will be my second (outer) leaf. The partition wall (blue) will be the outer leaf on that side.

If you desperately need that hallway, then yes, this is cool! Again, I'd use the whole space and find a wall somewhere else to hang my gardening tools or pedal bike.

I think I'll post this question as a new post as well, but I'd be interested to know what you think.

Try to keep all posts related to your build on this thread. It is impossible for members (including myself who is actively following your build) to jump around thread to thread trying to follow questions and answers pertaining to your design. It is okay to make a new thread if it is a generic question that hasn't been answered before. The cool thing about the search feature is that if anyone typed "pavilion roof", it would show this thread. Then, they could read about your entire design and hopefully learn something! Greg

Hi Gregwor Glad you like my attic - if not my rug ! Sadly, after talking it through with my wife, it is what it is, so I will have to make do with the partitioned space in the garage.

Gregwor wrote:

I know it may just be terminology here, but I thought we decided it is basically impossible to effectively build a fully decoupled inner leaf MSM room. Or are you still going to try and design it so it works? Again, I thought you were just going to use clips and hat instead?

Not sure what you mean by clips and hat. Can you elaborate? I've attached what looks to be the final plan, metaphorical warts and all. Once again, your views are appreciated. If I could do any part of this better within the parameters I've got? And yes, I take your point about keeping all the elements in one thread. Makes sense. Thanks John

Not sure what you mean by clips and hat. Can you elaborate?

I've attached what looks to be the final plan, metaphorical warts and all. Once again, your views are appreciated. If I could do any part of this better within the parameters I've got?

Your air gap and MSM looking diagram implies that you've figured out a way to do a true room in a room? I personally can't wrap my head around how you'll pull it off with the buttresses and angled roof. Also, your diagram states "compacted insulation". Insulation should never be compressed. The only way I can make sense of how you may pull this off is using the RSIC clips and hat like I posted above. Greg

Cheers Greg I have instructed my builder to use resilient bars - I've read this is a similar option to the clips? Regarding the compacted insulation - I did think that, as you wrote, insulation shouldn't be compacted as that will negate its dampening role. My builder suggested it to add mass to the existing exterior garage walls and roof - fix heavy duty insulation slabs pressed into damp proof membrane on the walls (or the felt on the roof) then use resilient bars to fix the double layer fire board over the top of this. While aiming to minimise any gaps. And then fix rockwool insulation with pins to this board on the inside, which would be the start of the air gap between my outer leaf and inner room wall. Would it be better to add mass to the outer boundaries with, say, plywood and fit the fire board to that, rather than trying to achieve more mass with insulation slabs? I appreciate your time and patience with me on this. John

Insulation is not mass. The density of insulation is about one twentieth that of drywall, so you would need to have it TWENTY TIMES thicker, just to get the SAME mass. In addition, the purpose of insulation is not even to add mass to the wall! The purpose of insulation is to damp the acoustic resonances going on inside the wall, as well as to change the way air deals with heat from adiabatic to isothermal, and in addition to slow down the speed of sound, and increase the acoustic depth of the gap. THOSE are the reasons why you put insulation in the wall, not to add mass. The insulation MUST be teh correct density for the task, in order to accomplish the above. If it is too dense, it will have very poor low-frequency damping characteristics, and if it is not dense enough then it won't have enough Gas Flow Resistivity to do the job. Use ONLY the correct TYPE of insulation, and the correct DENSITY. Do not, ever, compress it, as that destroys the very properties you bought it for! You really should read the book "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics). You do need to understand WHAT you are doing and WHY you are doing it, or you will make mistakes along the way. This book will help you understand. Resilient channel is not as good as the combination of isolation clips + hat channel, and neither of those is as good as a fully-decoupled inner leaf. But as Greg said, if you want to keep your framing the way it is, then you don't have many options. It's going to be a royal pain to get the drywall on the various angles of the ceiling and walls to line up and seal: you will have to work very, very VERY carefully to make that happen. - Stuart -

Thanks Stuart. I must say I am still confused. I understand what you're saying about using insulation for sound dampening, but I still thought I was going to achieve an almost fully decoupled inner room. My plan is to double board the existing roof and walls, and using insulation here was just an added element here. Then a totally separate inner frame which will not touch the beefed up garage walls and roof. (I know the main beams will go from inner to outer but that's something I'm going to have to risk. The inner wall will be framed round them and caulked where it meets. And I will see if I need to put sound board round them afterwards if needed. I know it's a long way from ideal, but I can't afford the work to take them down and put new higher ones in.) So if I've added mass to my outer walls and roof (double layer board green glued together, insulation outside that).. THEN I have my air gap (2 inches minimum)... THEN I have my inner room made from double layer board green glued together, mounted using clips, with dampening insulation on the outside of that, which doesn't touch the outer apart from the beams.. am I not getting good enough? I know "good enough" isn't ideal. Is your criticism of this whole plan based on the beams touching the outer structure? Thanks again. John

but I still thought I was going to achieve an almost fully decoupled inner room.

The only way you'll get "an almost fully decoupled inner room" is if your inner leaf is ONLY making contact through your concrete floor slab. If there is ANY elements of the outer leaf penetrating or even slightly touching the inner leaf, then it's game over. You might as well have not built your inner leaf. It's like playing the old board game called "Operation" where you try not to touch the guys body. But even a slight graze of your tool completes the circuit and the buzzer goes off.

My plan is to double board the existing roof and walls, and using insulation here was just an added element here.

If you do build a room in a room, you will need insulation between your inner and outer leaf. NO void space allowed!

Then a totally separate inner frame which will not touch the beefed up garage walls and roof.

Okay, with this design, it is "almost fully decoupled" and would yield the best results. However, the way your building is assembled, there are buttresses/gussets that stick out which would mean to avoid them, you'd have to build on the inner dimension of them which would make your room tiny. OR, see next point:

(I know the main beams will go from inner to outer but that's something I'm going to have to risk.

These buttresses/gussets will stick through your inner leaf and yield the entire room in a room concept useless. With some fancy planning, you might be able to design your inner leaf walls and ceiling such that you can avoid having these touch your inner leaf system and box around them to maintain your inner leaf mass and seal. There needs to be no risk involved. Either do a true MSM design, or don't.

The inner wall will be framed round them and caulked where it meets

Your entire outer leaf needs to be caulked. Then the inner leaf needs to be caulked. Two different "rooms", air tight. Neither of them should ever "meet" except at the concrete floor slab. Period.

And I will see if I need to put sound board round them afterwards if needed. I know it's a long way from ideal, but I can't afford the work to take them down and put new higher ones in.)

Don't build this on "I will see if I need" or "afterwards if needed". Build it with confidence. SketchUp a detailed plan and we will make sure your design will work before you lift up your hammer. Don't stress, we'll make sure you save money and have awesome results. I think you need to start 3D modelling this and see where problems will arise. From there, you will see where your plan will fail or succeed.

So if I've added mass to my outer walls and roof (double layer board green glued together, insulation outside that)..

Double layer board everything, yes. "insulation outside that" -- you mean "inside" right? Yes, you need insulation for your exterior wall, for sure.

THEN I have my air gap (2 inches minimum)...

No void. The insulation should entirely fill your wall space. This is the "spring" part of the Mass Spring Mass equation.

THEN I have my inner room made from double layer board green glued together,

If you do a true MSM design, yes, you would make your inner "leaf" (we call it leaf here, not room per say) frame. Then yes, you would have two layers of drywall with GG between them. Note: GG is just the name of the brand. It doesn't actually glue the boards together. It does the opposite actually. It's just like a snot. You still need to screw the drywall to the framing members. That's the end of your build process. See notes for the next point:

mounted using clips,

The only time you use clips would be if you do NOT build a MSM system. What I mean is, if you didn't frame an inner leaf, you would put clips on your outer leaf studs and joists, then fix drywall to them.

with dampening insulation on the outside of that,

There's more to treating your room than putting insulation on your walls, but yes, if you want to start your treatment stage with a dead room, and then bring it back to life according to your measurements, sure. This is typically the case when rooms are built inside out. If they aren't built inside out, it often makes sense to add insulation as your measurements determine. In your build description above, you're implying that you will build your walls conventionally, not inside out.

which doesn't touch the outer apart from the beams.. am I not getting good enough?

Not sure what you mean by having your treatment insulation not touch "the outer apart from the beams".

I know "good enough" isn't ideal. Is your criticism of this whole plan based on the beams touching the outer structure?

Yes. To repeat what I said above, if you have any part of your outer leaf (in your case your "beams") touching or sticking through, exposed to your inner leaf, it literally voids the purpose of the inner leaf all together. If this is the case, you're better off using clips + hat on your existing framing. It won't offer the amazing isolation that a fully de-coupled inner leaf would (especially at the low frequencies), but it is still decent, especially at higher frequencies. The clips are pretty expensive, but this method would save you quite a bit of space as well. To address a comment you made 2 posts back:

then use resilient bars to fix the double layer fire board over the top of this

Resilient bar is not the same as isolation clips + hat channel. Resilient bar makes a direct connection to the framing. Some is better than others, but with improved isolation comes the trade off of strength. The more holes in the bar, the more isolation it has. But, the more holes the bar has, the weaker it is. That's why isolation clips + hat channel is great. It is strong and the connection to the frame is through a rubber. There is also less chance of shorting out drywall screws to the framing when using clips and hat compared to resilient. I hope we are getting you closer to a usable plan here! Greg

1) Then a totally separate inner frame which will not touch the beefed up garage walls and roof. 2) ... the main beams will go from inner to outer ...

Those two statements are incompatible. It seems you are still not grasping the concept that a "leaf" is an entirely complete, "envelope" or "shell" that is absolute sealed air-tight, is not penetrated by anything, and has no mechanical connection at all with anything else: it stands alone, all by itself. There is no conceivable way that you can have a sealed shell with no connections to anything, and also have huge. massive beams penetrating through it. Think it through, and you'll see that there no way you can do that. EITHER you have a decoupled two-leaf system, OR you have beams from the outer-leaf that penetrate into the inner leaf. You can't have both.

but that's something I'm going to have to risk.

It won't be a risk at all! The result is absolutely predictable, and well-understood: If you have any solid mechanical connection at all between your inner-leaf and outer-leaf, even a single nail, then you have no isolation. If you don't believe me, then borrow an old-fashioned tuning fork from an old-fashioned musician, and do the following test: tap it on something solid, and hold it out in front of you at arms length: Can you hear it? Nope. At best, a very, very soft, distant, muted tone. Now tap it again, and put the base of the shaft down on the top of the desk or table in front of you, at arms length. Can you hear it now? You bet! Loud and clear. That tiny area at the bottom end of the shaft, is way more than plenty to create a very excellent acoustic connection. So imagine what half a dozen massive beams would do...

The inner wall will be framed round them and caulked where it meets.

And what will be the durometer rating of the caulk that you use? On which shore scale? How will you ensure that there is enough deflection in the caulk to cause it to isolate? What frequency will you tune it to? How will you ensure that it decouples? Caulk is meant for sealing, not for decoupling. Getting two objects to decouple is nowhere near as simple as just making a gap and filling it with caulk.... More likely than not, the caulk will couple them, not isolate them. The only time it would isolate is if you manage to get the durometer of the caulk just right, and force it into the gap just right, so that it has a static deflection of around 20% when it has cured.... I have no idea how you would even go about trying to accomplish that...

And I will see if I need to put sound board round them afterwards if needed.

HOw would you manage to do that, if your room is already built? You would need to cut large holes in your drywall so you can add the framing that you would need around the beams to support the "soundboard", and without any of that touching the beams, then somehow seal it all up again, air-tight, with the correct insulation in the air gap... Here's an equation that you should be using by now: If you don't recognize that, or don't know how to use it, then there's a big problem here. There's a simplified version, which assumes constant air paramaters: Fc=c[(m1+m2)/(m1m2d)]^.5 Where: c=constant (60 for empty cavity, 43 for cavity filled with insulation) m1=mass (surface density) of first leaf (kg/m^2) m2 mass (surface density) of second leaf (kg/m^2) d=depth of cavity (m) That's a lot simpler to understand. Once again, if you don't know what that equation does, then there's a problem.

So if I've added mass to my outer walls and roof (double layer board green glued together, insulation outside that).. THEN I have my air gap (2 inches minimum)... THEN I have my inner room made from double layer board green glued together, mounted using clips, with dampening insulation on the outside of that, which doesn't touch the outer apart from the beams.. am I not getting good enough?

Firstly, Green Glue is not adhesive, and you cannot use ot to "glue boards together". That's not what the product does, and attempting to use it as glue would be disastrous. Better go take a look at their website, to find out what the product is, what it does, and how to use it. But that's beside the point for your plan. Next, a 2" air gap is way too small: you need at least a 4" air gap, but your rafters appear to be 2x10s, at least, so I don't see how you could get just a 2" air gap in any case.... But that's also beside the point for your plan. The real problem with your plan, is this:

which doesn't touch the outer apart from the beams..

"apart from the beams". If even the tip of a tuning fork is enough to totally and completely couple the leaves, then how well do you think a 4x10 beam will do the job?

Is your criticism of this whole plan based on the beams touching the outer structure?

The beams don't just happen to "touch" the outer structure: they ARE the outer structure! Everything visible in your photos at present IS the outer leaf. All of the parts are in physical contact with each other, very firmly attached mechanically, and creating a wonderfully solid acoustically homogeneous single unit. Here's a test you can do: Go place your ear up against one of those vertical posts, and get someone else to tap on other vertical post with a small hammer, on the opposite side of the room: Do you hear the sound in the post? Yup, you sure do! Now look at the surface area of one of those posts. Let's say, for argument's sake, that those are 4" faces, 6 feet high. So there's a surface area of about 288 square inches on the face of each post. The surface area of a typical 8" speaker cone is about 50 square inches. So each of your posts has a surface area about 6 times larger than that of a speaker cone.... I think you are starting to appreciate the problem! Instead of looking at the posts, look at those beams spanning across your room: How much surface area do you think is in each beam, considering all four faces? For argument's sake, let's call it 2,000 square inches, to make the math easy. That's about the same as 40 speaker cones... OK, so a wood beam is nowhere near as efficient as a speaker cone, but I'd hazard a guess and say that it's a lot more than 1/40th efficient! So now so you see the dilemma? It does not matter how well you manage to seal and decouple those beams where they pass through the inner-leaf: simply because the ARE the outer leaf, you now have the outer-leaf INSIDE THE ROOM! And with a massive huge surface area, it will be able to both transmit all outside sounds into the room, as well as pick up all inside sounds and transmit them to the outside world... The problem is that your phrase ""apart from the beams" = "Zero isolation". As Greg pointed out: if any part of your outer leaf penetrates into your inner room, or even touches the inner leaf, then you don't have isolation, and you wasted a lot of money, time, and effort on building it.

and using insulation here was just an added element here.

You seem to have missed the point here too! Using insulation is not an "added element"! It is a basic, fundamental part of the isolation system! As I mentioned, insulation accomplishes many important tasks at once, including acoustic damping of resonances, changing the way air deals with heat, lowering the speed of sound, and others. If you do NOT put insulation in your wall, then you trash your isolation. The interior or your wall becomes an undamped resonant cavity... Insulation is not an optional add-on: it is an integral part of the MSM system. Take a look at the equation above, and you'll notice that the constant jumps from 43 to 60 if you don't put insulation in your wall. That's a HUGE jump! nearly 40% That's how much your f0 jumps up the scale, if you leave it out.... It seems that you are assuming a lot of things that are not correct, and no taking into account the things that you need to take into account. Any studio build starts (or should start!) with one very basic, simple number: "how much isolation you need", in decibels. If you don't know that, then everything you plan on doing is just wild speculation, and pure guesswork. Right now, neither we nor you have any idea how much isolation you need. All we know is that you need more than you are getting right now, but we don't even know how much that is! Your very first course of action, before you carry on with any of your plans, is simply to define how much isolation you need, in decibels. Get yourself a decent hand-held sound level meter, set it to "C" weighting and "Slow" response, and do a series of measurements to determine how much isolation you need, and set that number as the most basic parameter for your design. If you don't know that, then you don't know anything! There's nothing at all to go on. So do that first: get the meter, do the tests, and let us know your conclusion. - Stuart -

Thanks again Stuart and Greg Your advice has been very welcome indeed. How can I say this - but I've had a major rethink on the eve of the job starting. We have a large garden and I have decided to abandon the garage conversion idea and instead ask my builder (who I know is good and who I trust based on his previous work for us) to build a new structure from scratch. He's being incredibly accommodating and flexible considering he was due to start today, and is running with the change. So, we're looking at building a concrete base and then making something new. The available area is 6m x 4m. Again not huge but more than I would have had in the garage. I know that a brick built structure would be preferable, but it sounds that budget-wise, timber is more affordable for me. The last studio my band recorded in was a timber building, so I know it's doable. This will have block and brick up to damp level on top of a concrete base. Then timber. I fully appreciate I need to do a lot more reading and research, but my questions right now are: With those dimensions, would you recommend just a single room still? There would be enough space for a control room and a small recording room I believe. What would be the concept if timber is used for the bulk of the build? What should the roof/ceiling be made of? As it'll be a timber build, that will make concrete not an option. I've already done the research re planning permission and it will not be needed. I'm advised by my builder that building regs will (i.e. inspection). I live in a quiet lane, with no through traffic. Outside noise is minimal. The new location in my garden is away from other driveways even so there will be no car noise at all. I will as suggested get a meter and look into how much noise reduction I need to aim for. But for now, even your initial thoughts would be appreciated. And thank you again for the time you've spent on my garage idea. John

We have a large garden and I have decided to abandon the garage conversion idea and instead ask my builder (who I know is good and who I trust based on his previous work for us) to build a new structure from scratch.

That's probably a very smart move!

considering he was due to start today,

:shock: Ummmm... This is probably not a good time for you to find out, but just DESIGNING a stud fully usually takes a couple of months, and that's assuming that you already have a good working knowledge of both acoustics and also building design. I would really, really, really suggest that you put the entire build on hold for six months, until you can get it properly designed in full detail. If necessary, maybe pay your contractor something for his trouble so far, and let him know that he'll be re-hired once the new plans are finalized.

So, we're looking at building a concrete base and then making something new.

Your best bet is a monolithic slab on grade. Relatively fast and easy to pour, and an excellent base for a studio.

The available area is 6m x 4m. Again not huge but more than I would have had in the garage.

So 24m2 for the footprint of the slab? That's decent. Allowing about 30cm all around for the walls, that leaves you with an interior area of about 5.4 x 3.4, which is roughly 18m2. That's fine for a control room. With careful selection of materials and good design, there could be a bit more space than that, especially if it turns out that you don't need huge amounts of isolation.

I know that a brick built structure would be preferable, but it sounds that budget-wise, timber is more affordable for me. The last studio my band recorded in was a timber building, so I know it's doable.

That's fine. You can get excellent isolation and excellent acoustics with wood-framed construction on a monolithic slab. Here's an example: viewtopic.php?f=2&t=21368

This will have block and brick up to damp level on top of a concrete base.

That's an unnecessarily slow and expensive way of building a foundation. Unless the land slopes very steeply, the fastest, best, simplest, least expensive, least complicated foundation is a monolithic concrete slab-on-grade. It combines the footers and slab into a single pour, which can be done in a day. Of course, it takes time BEFORE that to dig the trenches and place the form work, but that's the same time you would have needed to dig the trenches for your proposed brick foundation.

I fully appreciate I need to do a lot more reading and research,

Yup! Realistically, that time will be about six months before you are ready to pick up a shove and move the first load of dirt to start the foundations...

With those dimensions, would you recommend just a single room still? There would be enough space for a control room and a small recording room I believe.

While it might be POSSIBLE to physically fit in a control room and a vocal booth, I wouldn't recommend it with only 18m2 to play with. The minimum recommended size for a control room is 20m2, according to specs such as ITU BS.1116-3, and EBU Tech-3276, among others. That's about as small as you can go and still get good acoustic response with simple treatment. It is possible to go to a smaller size, yes, but the smaller it is, the more complicated it gets to treat it and still get decent acoustics. And the smaller it is, the worse it will be from the point of view of overall frequency response, time-domain response, and specifically modal response. I'mnot sure if you have seen Martin's thread, but if not take a quick look: viewtopic.php?f=10&t=21539 That room is about 14m2, and it is giving us significant problem in getting the treatment right. Your room will be just a bit bigger than that, assuming you do not try to split it. If you DO try to split it in two, then it will be much smaller, and much more complicated. If you could go up to maybe 7m c 5m footprint, then yes, it would be possible to fit in both a control room and also a small vocal booth. That's the case with Kirk's studio, currently under construction: viewtopic.php?f=1&t=18270&start=15

What would be the concept if timber is used for the bulk of the build?

Still the same concept: fully decoupled 2-leaf MSM construction. In other words, you build one stud frame on the edge of the foundation slab, and put weather-proof sheathing on the outside of that frame (no sheathing on the inner face of the framing!), then you build a second stud frame about an inch away from that, and put sheathing on just ONE side of that framing as well. Fill the entire cavity with suitable insulation.

What should the roof/ceiling be made of? As it'll be a timber build, that will make concrete not an option.

Actually, you COULD do a concrete roof a timber framed walls if you really wanted to, but it would be complex and takes up too much space for the larger-sized framing. It's better to go with wood framing all around. So, you would build some type of roof that rests on the outer-leaf walls, and you would have two options in how to do that: 1) Build it as a sealed roof that needs no ventilation under the deck, and thus allows you to put the mass directly on the roof. Or 2) Build it as a typical ventilated roof, where air flows under the roof deck to keep it cool in summer and prevent condensation in winter, which implies that the roof cannot be the outer-leaf of your MSM system, so you will need to have a "middle leaf" ceiling of some type, below the roof, to complete the sealed envelope of the outer-leaf. If you take a close look at the corner control room threas, you'll see that's exactly how we did it for his studio. There's a typical vented roof up there, then a vaulted "middle-leaf" ceiling under that, which creates the top of the actual outer-leaf shell. That's the reason for the raised-tie roof trusses: to gain extra height under the exterior roof, for the "middle-leaf" ceiling, so that the final inner-leaf ceiling can still be nice and high. One option for using your garage would have been to modify your existing roof trusses to make them into raised-tie or collar-tie, but that's not so easy to do for your shape of roof. Possible, but not simple. So in both of these cases, once you have completed the outer-leaf shell of the building, fully sealed, air-tight, and with consistent mass (surface density) all around, then you can build your inner-leaf ceiling below that. The inner-leaf ceiling sits on top of the inner-leaf walls, and the most efficient design is the "inside-out" method, where you build a sturdy "backbone" frame work, then raise several "modules" in between the members of the frame. Once again, the corner control room studio is a good example of that: you can see how it was built from the photos on his thread.

I've already done the research re planning permission and it will not be needed. I'm advised by my builder that building regs will (i.e. inspection).

So you are going to do this under "permitted development" rules? IF so, be careful with that! There are restrictions on the maximum height you can have for the roof. That's what Kirk ran into: Even though he went with a flat "bloc-and-beam" roof, there still would not have been enough height to fit in the HVAC system and also still get good acoustic height for his studio. Which is why we decided to dig down a bit laying the foundation below ground level, with some steps down. That allows him to have plenty of room height (which is critical for good acoustics), and still not exceed the "permitted development" regulations. I'd suggest that you consider doing this in your case too! That does mean that you can't have timber-framed walls below ground level, though. You could do yours the same as Kirk did up to ground level, then timber framing above that, or you could just do the whole thing the way he did.

I live in a quiet lane, with no through traffic. Outside noise is minimal. The new location in my garden is away from other driveways even so there will be no car noise at all.

So there is nothing in Cheshire that could trash your recording sessions? No thunder, rain, hail, or wind? No aircraft or helicopters flying over? No sirens from ambulances / police / fire engines? No trains? No cars arriving / leaving / driving past? No dogs barking outside? And nothing in the nearby houses either, such as water running in pipes, fans, pumps and other motors, people walking on floors, doors closing, people talking, vacuum cleaners, washing machine, radio, TV, furnace.... There's hundreds of possible sounds that could destroy a good recording, if they get into the mics in your control room. Are you CERTAIN that your room will not get any of that? :)

I will as suggested get a meter and look into how much noise reduction I need to aim for.

A while back I wrote a post about how to test a room acoustically, to decide on treatment, and you need a sound level meter to do that. So part of that thread describes what to look for when buying a sound level meter: viewtopic.php?f=3&t=21122 . You can ignore the rest for now (you'll need it a year from now, when your room is completely built, and you are about to start treating it...), but do take a close look at the part about meters.

But for now, even your initial thoughts would be appreciated.

The best advise I can give you at this point is: slow down! Put the construction on hold for at least six months, perhaps as much as a year, and take the time to firstly learn all the basics of acoustics, then to learn all the basics of construction and construction design, then to learn how to use SketchUp, then to actually design your place, in complete detail. Once the design is finished, in all aspects and complete detail, only then can you start thinking about calling your contractor again, and ordering materials and tools. So please just use this same thread to document your design process as you work through it, and then your actual build. - Stuart -

Thanks Stuart. I appreciate your latest advice. And yes ideally I would wait and do more preparation, but for various compelling reasons which I won't go into here, that's not an option. Work starts tomorrow and I hope I've picked up enough from your (and Greg's) input to make a good job of it. I do hope you won't abandon me, and help me as best you can in these circumstances!

That's an unnecessarily slow and expensive way of building a foundation. Unless the land slopes very steeply, the fastest, best, simplest, least expensive, least complicated foundation is a monolithic concrete slab-on-grade. It combines the footers and slab into a single pour, which can be done in a day. Of course, it takes time BEFORE that to dig the trenches and place the form work, but that's the same time you would have needed to dig the trenches for your proposed brick foundation.

There is a slope close (but not too close) to the build. And my builder already knows the ground as he excavated it to build a patio and a deck. So a monolithic slab is not an option he tells me.

Still the same concept: fully decoupled 2-leaf MSM construction. In other words, you build one stud frame on the edge of the foundation slab, and put weather-proof sheathing on the outside of that frame (no sheathing on the inner face of the framing!), then you build a second stud frame about an inch away from that, and put sheathing on just ONE side of that framing as well. Fill the entire cavity with suitable insulation.

Thanks for this summary. From this I read that we're overdoing it. From the outside of the building, the current plan is : Pine cladding fixed directly onto OSB board fixed to Timber framing Between the batons: Rockwool RW3 100mm insulation (density 60 kg/m3) Small air gap Rockwool RW3 100mm insulation Timber frame Double thickness fire board (with green glue between) fixed directly to frame Do I need all of this? The OSB board for instance? If this is still not giving me MSM with full decoupling, I must be infuriating you. Please count to ten.. again.. and tell me in the same format as above what I should do?

Actually, you COULD do a concrete roof a timber framed walls if you really wanted to, but it would be complex and takes up too much space for the larger-sized framing. It's better to go with wood framing all around. So, you would build some type of roof that rests on the outer-leaf walls, and you would have two options in how to do that: 1) Build it as a sealed roof that needs no ventilation under the deck, and thus allows you to put the mass directly on the roof. Or 2) Build it as a typical ventilated roof, where air flows under the roof deck to keep it cool in summer and prevent condensation in winter, which implies that the roof cannot be the outer-leaf of your MSM system, so you will need to have a "middle leaf" ceiling of some type, below the roof, to complete the sealed envelope of the outer-leaf. If you take a close look at the corner control room thread, you'll see that's exactly how we did it for his studio. There's a typical vented roof up there, then a vaulted "middle-leaf" ceiling under that, which creates the top of the actual outer-leaf shell. That's the reason for the raised-tie roof trusses: to gain extra height under the exterior roof, for the "middle-leaf" ceiling, so that the final inner-leaf ceiling can still be nice and high. One option for using your garage would have been to modify your existing roof trusses to make them into raised-tie or collar-tie, but that's not so easy to do for your shape of roof. Possible, but not simple.

My builder tells me he's planning a 'warm roof' which I assume is the same as a sealed roof. Like the walls, from the outside he's planning weather resistant covering, membrane, OSB board, the Rockwool RW3 insulation, timber frame.. air gap, Rockwool RW3 100mm insulation, timber frame, double thickness fire board (with green glue between) fixed directly to frame (not using resilient clips as I believe it's decoupled inner room). Above the inner leaf will be acoustic venting ducts that lead down to vents in the inner ceiling for air in and out (if need be with silencer boxes mounted under the inner ceiling). So it's the same question as per my walls above. But also, will a sealed roof like this be OK? Or do I need to do the middle leaf to address a possible condensation issue?

So you are going to do this under "permitted development" rules? IF so, be careful with that! There are restrictions on the maximum height you can have for the roof.

I believe I have checked all the regulations. Because the building will not be within 2m of the boundary, I can go up to 3m - see attached snip from the local government website.

So there is nothing in Cheshire that could trash your recording sessions? No thunder, rain, hail, or wind? No aircraft or helicopters flying over? No sirens from ambulances / police / fire engines? No trains? No cars arriving / leaving / driving past? No dogs barking outside? And nothing in the nearby houses either, such as water running in pipes, fans, pumps and other motors, people walking on floors, doors closing, people talking, vacuum cleaners, washing machine, radio, TV, furnace.... There's hundreds of possible sounds that could destroy a good recording, if they get into the mics in your control room. Are you CERTAIN that your room will not get any of that? :)

I fully appreciate what you are saying but it is indeed a very quiet environment. But I believe what I am doing will give me the isolation I need. Finally, I did look at the threads you suggested. Some very impressive work indeed. I am honestly not aspiring to that level at this point in my life. Maybe I will one day. I will have to do my learning in the place I'm having built. Stuart, I know it's not what you like hearing, and I totally realise you have my best interests firmly in mind, but this is happening and I'd rather put out to sea in this craft with you as a virtual mate. Thank you again. John

I'm strapped for time, but I will say this (if you're starting tomorrow): DIG DOWN BELOW GRADE!!!! Your silencer boxes and HVAC take up a TON of room. Your ceiling height will be very very short if you don't go down some. Try to gain even a few feet. The more, the better though. Seriously, trust me on this one. You NEED the height! Also, I understand there is some "compelling reasons" you have to start the build now. I won't say that's fine, but okay, you must start. I get it. Stop as soon as you're allowed to stop though. If that means getting the shell up and then you can break, do it. You literally cannot build something this complex without a 3D plan and a bunch of calculations. We care, we don't want you to fail. Also, if you can stretch those dimensions at all, even a quarter of a meter, do it. I look forward to your progress pics tomorrow night from the build start tomorrow morning! I hope *fingers crossed* that I see a deep hole being dug. . . Greg

And yes ideally I would wait and do more preparation, but for various compelling reasons which I won't go into here, that's not an option

I really hate to be harsh, but sometimes a rude "wake-up call" is what you need, so here it is: If it is not an option to stop building now, then it is not an option for you to have a successful studio. Period. Stop. End of story. It really is that simple. You CANNOT successfully build a studio without proper planning. It WILL NOT WORK. That's about as categorical and in-your-face as I can make it. So the choice is yours: Start building tomorrow and fail. Or be sensible, stop building, plan properly, and succeed. We have seen this happen time and time again on the forum: People absolutely convinced that they MUST build RIGHT NOW, and that their extreme urgency will somehow invalidate the laws of physics, allowing them to bypass the fixed rules of nature that everyone else must live by. Because it is life-or-death for them, the Universe realizes this, and will allow sound to NOT follow the normal rules, but only for their specific situation, just because they are in a hurry.... Sound will bow down to them, because their situation is so important.... Not gonna happen! Sound waves will behave exactly as they always do, for your studio, just like everyone else's. In every single case where we have seen this on the forum, not one has succeeded. None. Zero. Zilch. I very much doubt your case will be the first... In every single case where this route has been followed, where we have warned people to stop, wait, design, then carry on, and they have ignored our advice, believing that they know better, and their situation is "different", not one has ever produced a successful studio. In fact, not one has even produces a studio at all! Let that sink in for a minute. Why would your case be any different? The ONLY times that there has been success, is when people have heeded our advice, stopped, planned properly, and built it right. In some cases, they even had to tear down stuff they had built wrongly already, then start again. Such as this one: viewtopic.php?f=2&t=17363 (read the first few posts, carefully....)

I do hope you won't abandon me, and help me as best you can in these circumstances!

I'll try, but I really don't hold out much hope of being able to help someone who has made a conscious decision to fail.

And my builder already knows the ground as he excavated it to build a patio and a deck. So a monolithic slab is not an option he tells me.

Really? That sounds very strange! The experts normally recommend monolithic slabs precisely FOR difficult ground... I'm wondering if your builder maybe has a vested interest in going with the long, slow, expensive process, that will put a LOT of extra cash in his pocket (a couple of thousand pounds extra, at least, probably...) rather than the fast, efficient, low cost process? I wonder .... Hmmmm..... It makes you think, doesn't it? Fact: Your builder is NOT qualified to make this decision. A soils engineer or structural engineer is the ONLY guy who can tell you the right way to do this. Period. Do NOT make the mistake of trusting the guy who stands to make a stack of money, when making major, key decisions like this! Trust the qualified, certified export engineer, who has no vested interest at all, and actually does know what he is doing. Before you do anything, hire one, tomorrow morning. Get him in, and get his report. Tell him you'd like a monolithic slab, and ask if there is any good reason why that would not be good for your situation. Ask him to explain, clearly, what the pros and cons are of the various types of foundation. There's only one problem here: he'll want to know what total load you are going to put on your foundations, but you don't have a clue about that, because you have not planned a single thing about it! You have no idea at all what your dead load and live load will be: So how in hell can your "builder" tell you what dimensions, materials, and techniques you will need for doing the foundation? How can he even give you a cost estimate, when nobody yet knows how much weight the foundations have to support? This makes no sense at all.... Does your builder even know how to do a monolithic slab? What specific structural reason does he give you for his suggestion? Not just "Well, gee, umm... I think... errr... I don't like doing it that way", but an actual, structurally valid reason.

Thanks for this summary. From this I read that we're overdoing it.

Why do you think that is overdoing it? Isn't that exactly what I said in my post?

Pine cladding fixed directly onto OSB board fixed to Timber framing Between the batons: Rockwool RW3 100mm insulation (density 60 kg/m3) Small air gap Rockwool RW3 100mm insulation Timber frame Double thickness fire board (with green glue between) fixed directly to frame

In what way is that different from what I said? Also, did you use this equation yet? " Fc=c[(m1+m2)/(m1m2d)]^.5 " I gave it to you yesterday, and mentioned that if you do not understand it, or do not know what it means, or have not yet used it, then there is a SERIOUS problem here! It is one of the most basic, simple, KEY equations that you MUST use on your walls, if you hope to avoid failure. "Failure" can take two forms here: 1) you finish the place and the isolation is so lousy that it is not usable as a studio. 2) You finish the place and have much more isolation than you need, which is nice, but it also cost you much more than you should have paid, so the only guy who wins is the builder.... again.... Learn what that equation means. USE IT! Then base your build on the results you get. If not, then there's no point me trying to help you any further.

My builder tells me he's planning a 'warm roof' which I assume is the same as a sealed roof.

"Assuming" is a very, very bad way to design a studio. Starting a build without even having the complete plans in hand, either electronic or on paper, is a plain stupid way of building a studio! Do you have the complete plans in hand? Sorry to be so harsh again, but if there's one thing that I'm known for on the forum, is calling it like I see it. No beating about the bush. No pulling punches. No PC crap. Just laying it out in front of you, in all it's ugly glory. IF you start building a studio, and you do not have the plans in place, that's stupid. I have no other way of describing it. Show me the detailed plans for your "warm roof", exactly as it will be built in your specific case, with all the dimensions, and then I can tell you if it is what you need, or not.

My builder tells me he's planning a 'warm roof' which I assume is the same as a sealed roof. Like the walls, from the outside he's planning weather resistant covering, membrane, OSB board, the Rockwool RW3 insulation, timber frame.. air gap, Rockwool RW3 100mm insulation, timber frame, double thickness fire board (with green glue between) fixed directly to frame

What the dimensions for the lumber? What span? What is the truss design? What live load and dead load did you use for the loading calculations? What deflection are you considering for the joists? What decking will be used? What is the slope of the roof? What is the nailing schedule? What is the membrane? What is the final finish surface of the roof? How much will it weigh? What is the surface density? What is the MSM f0 frequency in combination with the inner-leaf ceiling? If you cannot answer those questions directly from the plans you have in your hand right now, then it would be foolhardy for you to proceed. Not knowing all of that is sure sign that there is no planning going on here, and that's a certain indicator of failure. Guaranteed. Let's take this piece by piece: "weather resistant covering" - What type? How thick? What mass? What surface density? How is it attached? "membrane" - What type? How thick? What mass? What surface density? "OSB board" - How thick? What surface density? How is it attached? How are the joints between boards sealed? "Rockwool RW3 insulation" - How thick? Why? Why not semi-rigid fiberglass? Or fluffy fiberglass? Or cellulose? Or something else? How will it be held in place? "timber frame" - What dimensions? What span? What load is on that (live and dead)? Wheat deflection? "air gap" - How big? Why do you want empty air in your cavity, when I already spent a lto of time explaining that your cavity should be completely filled for maximum isolation? Did you not understand the difference between the constant being 43 or 60 in the equation? "Rockwool RW3 100mm insulation" - Why? "timber frame" - Dimensions? Span? Load? Deflection? "double thickness fire board" - What thickness "fire board"? What is "fire board"? Surface density? Attachment? Seals? "with green glue between"- Why? What coverage pattern? Etc. So many questions... and I'm betting there are very few answers...

(not using resilient clips as I believe it's decoupled inner room)

You just "believe" that it is decoupled? You don't KNOW this for a fact? Yet you plan to start building tomorrow? :roll:

Above the inner leaf will be acoustic venting ducts that lead down to vents in the inner ceiling for air in and out (if need be with silencer boxes mounted under the inner ceiling).

Where is the AHU? What is the heating/cooling/dehumidifying capacity of that unit? What sensible heat load did you consider in your calculations when you decided on that unit? What latent heat load? What occupancy? What flow rate did you calculate you need for your room? What will the flow velocity be at the registers? How much make-up air will you be adding? How much stale air will you be dumping? What size duct work is the correct size for this situation? Will that be rigid or flexible? Lined or not lined? What will the static pressure drop of your system be? Can the AHU handle that static pressure load? How will you prevent the pipe bundle from flanking between leaves? Where will the heat pump go? Where will the condensate drain go? If you did not understand all of those questions immediately, without googling them, and if you don't have all the answers in your plans already, then you have no business building this place yet: it will fail, since it will not be ventilated correctly. The simple, and rather silly, explanation that your builder gave you of " venting ducts that lead down to vents in the inner ceiling for air in and out" shows that he does not actually have a clue about studio HVAC. What on earth is an "acoustic venting duct"? I've never heard of one of those! I've been designing HVAC systems for studios for many, nany years, and I have never come across that term ever before. Because it's somthing your builder invented himself, on the spur of the moment, since he doesn't actually have a clue.

(if need be with silencer boxes mounted under the inner ceiling)

You are kidding, right? Do you have ANY idea how BIG such boxes are? Clearly not. I certainly would not want one of those hanging from the ceiling in my studio! Take a close look at this image: it shows the dimensions for the HVAC duct system for a small control room that I designed for a customer a few years back. The room is very similar in size to your room, so you WILL need something like this: That is a "bird's eye view" from above the control room ceiling, looking down onto the inner-leaf ceiling, with the outer-leaf removed: all of that HVAC system goes in the space between the inner-leaf ceiling and the roof (or middle-leaf ceiling, as the case may be). Do you REALLY want all of that hanging from your ceiling, inside the room? (This is probably the point where you and your builder will come up with a whole slew of reasons why you think you don't need an HVAC system for your room, but I can tell you in advance, before you even mention them, that I've heard them all before, and not one of them is valid: you DO need an HVAC system for your studio, if you plan on staying alive and healthy in there. There is no argument here. HVAC is not a luxury for a studio: it is a basic requirement. It is every bit as necessary as having a roof on top and walls around you. So please don't even wast your time trying to tell me why YOUR case is different, and the universe will also suspend the biological laws that govern your metabolism and how your respiratory tract works, just because you are in a hurry.... :) )

But also, will a sealed roof like this be OK?

I have no idea, until you show me the detailed plans. I have no idea what your builder means be "sealed roof" or "warm roof". Different meanings to different people in different building codes... A quick check on Google found this "definition": "A warm roof construction has many benefits over a traditional ‘cold roof’, essentially it is a ‘breathable roof construction’, which allows moisture to escape which in turn prevents damp and any associated decay problems. " If it is breathable, and allows moisture to escape, then it is NOT sealed, so it is NO use for your situation, unless you also add in a middle-leaf.

Or do I need to do the middle leaf to address a possible condensation issue?

Based on the above definition, it certainly seems that way! On the other hand, since your builder doesn't seem to know what he's talking about with foundations or HVAC, it is enturely possible that he's misusing the term "warm roof" as well, and to him it means something totally different. I can't tell what he has in mind until you show me the actual final plans for your specific "warm roof". Show me those, and I might be able to say. But I'm not talking about generic plans for other warm roofs: I'm talking about the specific, actual, real plans for your specific studio, drawn in complete detail, and approved by your local authorities. Show me those plans, and I can tell you if that will work, or not, acoustically.

I believe I have checked all the regulations.

Are you certain? The most recent version I have is 978-1-4098-5046-5, dated April last year. IS that what you have? That's what I used the last time I designed a studio for a customer in the UK. I'm assuming you are presenting this as a Class E situation? You say the ground slopes slightly? Did you notice what point you have to measure your 2.5m, 3m, or 4m height from? Did you notice that, regardless of the height of the roof peak, your eaves cannot be higher than 2.5m? No, I didn't think you noticed that. Did you realize the implications of this limitation? No, I figured you didn't realize that either: it places a limit of 2.5 m on your outer-leaf wall height (since that is where you MUST measure your eave height), which implies an even lower height for your final inner leaf ceiling. Depending on span and construction, and allowing 40cm for the silencers, your final inner-leaf ceiling will be around 2m, maybe lower. Explain to me how you hope to get usable control-room acoustics for a ceiling that low... That's a little under 6'6".... (I hope you are not too tall, and don't get claustrophobic...) You mean you did not know this already? That your assumptions and lack of understanding would lead to a room with an unworkable low ceiling height? You would have soon figured that out, if you would have planned properly. Here it is, in black and white. Page 44: So no matter how high your roof can go, your walls CANNOT exceed 2.5m at the eaves. And that places a severely low limit in the inner-leaf ceiling. :roll:

I can go up to 3m

... assuming you do a shed roof, that's possible, yes. And for a gable roof, it could be 4m! But as paragraph (f) clearly states, your walls can be no higher than 2.5m at the eaves. THAT is the problem, not what you ASSUMED was the problem.

see attached snip from the local government website.

I'm well aware of what permitted development regulations for the UK state: I have designed several studios for customers, under these. One of them is Kirby's place, that I linked you too. And the above is the exact reason he decided to bight the bullet, and dig deep. His "eave height" is exactly 2.5m, but the internal outer-leaf shell height is 3.5m (11'5", roughly), and the inner-leaf ceiling height of his control room and iso booth, (with complete HVAC above) is 2.8 m (about 9'2"). Very decent, and very usable, acoustically. The final visual ceiling height in the control room, with all acoustic treatment in place, is 2.66m (not counting the cloud, of course). That's about 8'6" in imperial.. Higher even than the standard UK ceiling height, of 2.4m...

But I believe what I am doing will give me the isolation I need.

And fifteen years ago my kids believed in Santa Clause... but then they grew up, learned about reality, and now they no longer believe in that.... :) In other words, what you BELIEVE and what is REAL can be two very different things. The only way to tell if you will have the isolation you need, is to do the math. Just believing it to be enough will not make it so, any more than a small child believing in Santa actually makes him exist. Believing and hoping and assuming, and guessing are really, really terrible ways to design a studio...

Finally, I did look at the threads you suggested. Some very impressive work indeed.

Take a close look at Kirk's thread: That is exactly what you need, and was built under Permitted Development, Class E. It's not far-fetched, "out there", or unreasonable: it is realistic. His will have a bathroom, kitchenette, isolation booth, control room, and entrance lobby. All within a 33.5m2 footprint. You could do the same. Or you could go smaller, and skip the extra rooms, leaving just the control room. Which is nearly 15m2 floor area, in Kirk's case, and could be about the same in your case.

I am honestly not aspiring to that level at this point in my life.

Then I don't understand what you are aspiring for! If you are NOT looking for a workable, usable, realistic control room on a 25m2 footprint with good isolation and good acoustics, built under Class E permitted development rules, then I must have entirely misunderstood your thread! That's what Kirk's thread is about.

Stuart, I know it's not what you like hearing, and I totally realise you have my best interests firmly in mind, but this is happening and I'd rather put out to sea in this craft with you as a virtual mate.

I'm not going out to sea on a boat that I suspect will sink! I'll happily watch from shore, and shout encouragement every now and then, if you want, but I do hope you know how to swim, because your boat ain't gonna float... - Stuart - PS:

DIG DOWN BELOW GRADE!!!!

YES!

Your silencer boxes and HVAC take up a TON of room.

YES!

Your ceiling height will be very very short if you don't go down some.

YES!

You NEED the height!

YES!

Also, I understand there is some "compelling reasons" you have to start the build now. I won't say that's fine

Neither will I! In fact, I'd say that unless the "compelling reasons" is a guy standing next to you with a gun against your head, telling you he will pull the trigger unless you start tomorrow... then there's no reason at all to actually start tomorrow. It's foolish. This is like he said he wants to go on vacation, and is leaving tomorrow: You ask here he is going, and he says "No idea". How are you getting there? "No idea". Plane? Train? Car? Bus? Bicycle? Roller-skates? "No idea". How long will it take? "No idea". What clothes did you pack? "No idea". How much will it cost? "No idea." What will you eat? "No idea". Do you have any idea at all where you are going? "On vacation! And I really REALLY have to leave tomorrow... even though I don't have a clue about where I'm going or what I'm doing".... :shock: That's what I'm reading above.

You literally cannot build something this complex without a 3D plan and a bunch of calculations.

YES! Very, very true.

I hope *fingers crossed* that I see a deep hole being dug. . .

I'd differ slightly here: I would MUCH rather see nothing at all happen tomorrow, except that the entire thing gets put on hold, and common sense takes over.... But I'm not expecting to see that either....

Well, three days later, and no response, so I guess that's yet another "I know better than you guys, and I'll do it my way and it will be fantastic!" response. Please do keep updating the thread with photos of the build, so we can see how you do it, and how it works out for you, even if you don't want our advice any more. - Stuart -

OK I'm back. Ready for some more haranguing yes, but I know I'm getting good advice as well, so here goes.. I haven't stopped the job. BUT I have done a lot of thinking and talking with my builder and the plan has changed. I'm going to have concrete block exterior walls now instead of a timber outer. The interior decoupled room within a room will be a timber frame with double layer acoustic board as before (walls and ceiling). I've asked him to dig down as suggested here to give me more interior height. I've properly looked at the planning and building regs as advised here and now understand what I can do. I'd appreciate help on the the exterior roof. My budget definitely won't stretch to a concrete roof. Should I tile it and have acoustic board above the rafters (or will OSB suffice). Then there'll be my gap - within insulation - before the inner ceiling of double acoustic board as above. Will this be sufficient mass? How can I beef it up if needed? Also, on the exterior block walls, my builder is talking about putting batons on the outside of the block, and putting timber cladding on them. Will the gap between the block and the cladding matter? Should I insulate that? OK. I've donned a second thicker skin and am holding my breath. John