Does this count as a 'leaf'

Ok - thanks to this lovely forum I have now had the chance to look at lots of different people's solutions and designs for ventilation that I can do my best to emulate...they clearly vary in terms of size...the number of baffles....and then more sophisticated things to do with air entry/exit opening sizes etc... But I still have a couple of fairly basic questions... 1. Looking at the pic below (which is a relatively small build) - I am still finding it hard to see how, having created lets say 5 layers of plasterboard in two leaves...with not a single air gap - to mimimise sound transfer from inside the inner room - to outside the outer room....if I then build two air ducts (albeit with a couple of twists and turns for the air) that are 6" or so across - then surely I am going to massively undermine my sound isolation?? Or am I missing an obvious bit of physics here?? 2. I haven't managed to work out what people are doing to make sure that the ventilation system doesn't effecitvely become a 'contact' between the inner and outer rooms. Stuart was kind enough to reply to a PM of mine re electricals that said On the electrical cable: Yes, it does have to touch both, but it isn't really a problem. Use PVC conduit for that cable, and angle it vertically or horizontally over a couple of feet between the two leaves (on other words, where it comes through one leaf, put a 90° curve so it runs parallel to the drywall, run it a couple of fee then put another 90° curve so it can go through the other leaf. Then cut out a section in the middle, an inch or so long, and wrap that gap with a trip of soft flexible rubber, to de-couple the conduit from both leaves. The wiring itself won't flank much. When you have it wired, stuff a small piece of insulation into each end of the conduit, then put a db of caulk over that, to seal it. The key to good isolation is to seal EVERYTHING! Both leaves must be totally air tight. Is there something equivalent I should be doing with the ventilation ducts? I am assuming that these silencer boxes will be located between my inner and outer rooms...and physically attached to the inside of the outer wall? The fan could be inside too - but I imagine it will be easier...and smarter from a maintenance persepctive, to locate the fan on the outside of the outer wall...in an adjacent room - where I can get at it if it fails! But at the point where the duct (solid or flexible) meets the inner room wall, it will have to be fixed in place? 3. Just an aside - just in case there are any Aussies reading this fab forum - do you know a good place to get the lining duct for ventilation boxes that is mentioned widely on this site - is it a plumbing supplier? And what about those backing rods used when beefing up walls - any suggestions on suppliers down under? Thank you once again P

Soundman2020 wrote:

You still attempting to make this build in an elevated wood structure Peter?

No, he's building it in his basement, on a slab, but with a wood framed floor above him.

Ok, you say basement, but peter has mentioned once, a rehearsal room on an elevated wooden floor and second a brick house...I have not seen the word basement. So peter...could you clarify for me at least since each type of structure has its own known issues and methods to overcome and some known "live with its", what type of structure(where is the room located) is it you are actually trying to do this build inside of?

Hi and thanks for keeping an eye on the thread. Yes it is definitely NOT an elevated structure....it is the lowest level of a 2.5 level house built on a hill (there's a picture in an earlier post). The music room sits on the concrete slab. The main living area is directly above (it's a timber framed, brick veneer construction) The sleeping area is above and back...you can crawl over the retaining wall at the back of the music room, up the hill (the house is on piers at the back) - to the area under the bedrooms. P

If you have settled on this thread to be the main one, then maybe you could let us have some pictures of all these things you discuss, you know what they say...a picture speaks a thousand words.

Sure - all the pictures are on this thread - here's the main one again....it says it all - well most of it! Thanks again. P

In addition to my recent questions (about 5 posts above this one - the one with the pic of a ventilation box)...that I'd love some help on please when someone has a moment... I have one other quick question (that impacts what I do with some cornicing I have ready to take back to the shop!)...; On some threads I have seen mention of techniques - gaps etc being used to make sure that the walls don't touch the floor...and more significantly for me right now - making sure that the walls don't touch the ceilling. The rest of my downstairs area has a plaster cornice that joins the wall to the ceilling - it's a cosmetic thing that saves a builder time doing square edges! Now I was going to continue those cornices into the music room - but that's not practical if the walls and ceilling are not supposed to touch....NB my build is a room within a room so these walls and ceilling are not touching the outer leaf in any way at all. Thanks again. P

peter1908 wrote:

Sure - all the pictures are on this thread - here's the main one again....it says it all - well most of it! Thanks again. P

That does not say it all :) A real picture of the real room...that would say more.

I have seen mention of techniques - gaps etc being used to make sure that the walls don't touch the floor...

I'm not sure what you mean there: The walls kind of HAVE to touch the floor! :shock: :) Or are you talking about floating the floor? In other words, building the walls on one foundation, and the floor on another foundation with some form of tuned spring system to keep it floating? That can be done, but the expense is enormous, and it is not easy to do. Very few studios need to go to such extremes.

making sure that the walls don't touch the ceilling

Well, the walls CAN touch the ceiling, provided that they only touch THEIR OWN ceiling. In other words, the outer-leaf wall framing supports the outer leaf ceiling framing, and the inner-leaf wall framing supports the inner-leaf ceiling framing, with no connections between outer-leaf and inner-leaf. That's the concept of "room-in-a-room": you build a complete room, all four walls plus the ceiling, totally within and separate from the outer room. Yes, if really want to maximize every last decibel of isolation, then it's a good idea to leave a small gap around the actual inner-leaf ceiling drywall itself, where it would otherwise touch the inner-leaf wall drywall, and seal that gap with caulk, to help reduce flanking through that path, but the actual ceiling framing normally rests on the actual wall framing anyway, so this isn't going to buy you a huge amount of extra isolation. That said, every little bit helps!

The rest of my downstairs area has a plaster cornice that joins the wall to the ceilling - it's a cosmetic thing that saves a builder time doing square edges! Now I was going to continue those cornices into the music room - but that's not practical if the walls and ceilling are not supposed to touch

You can still do cornices if you want to, even if you do leave a caulked gap around the edge of the ceiling drywall: Just attach the cornice to the wall ONLY, leave a small gap above (a few mm), where it would normally touch the ceiling. For example, put a thin separator, such as strips of cardboard, wood or plastic shim, or something similar, between the cornice and the ceiling while you are attaching it, to create the gap, then take out the separators once the cornice is in firmly place. Voila! Cornice with an air gap! You won't notice the gap from below, unless you look carefully. - Stuart -

Thanks Stuart. - no I'm not after a floating floor - I just read references to laying a strip along the floor when putting on the bottom sheet to keep the sheet from touching the floor...and then caulking afterwards - and the reason I asked the cornice question is because I'm not that good at it - and a bit of filler top and bottom usually improves the look of my work! All the best Peter

I wonder if I could repost this as it is now back on the previous page and I'd really appreciate any thoughts! .....thanks to this lovely forum I have now had the chance to look at lots of different people's solutions and designs for ventilation that I can do my best to emulate...they clearly vary in terms of size...the number of baffles....and then more sophisticated things to do with air entry/exit opening sizes etc... But I still have a couple of fairly basic questions... 1. Looking at the pic below (which is a relatively small build) - I am still finding it hard to see how, having created lets say 5 layers of plasterboard in two leaves...with not a single air gap - to mimimise sound transfer from inside the inner room - to outside the outer room....if I then build two air ducts (albeit with a couple of twists and turns for the air) that are 6" or so across - then surely I am going to massively undermine my sound isolation?? Or am I missing an obvious bit of physics here?? 2. I haven't managed to work out what people are doing to make sure that the ventilation system doesn't effecitvely become a 'contact' between the inner and outer rooms. Stuart was kind enough to reply to a PM of mine re electricals that said On the electrical cable: Yes, it does have to touch both, but it isn't really a problem. Use PVC conduit for that cable, and angle it vertically or horizontally over a couple of feet between the two leaves (on other words, where it comes through one leaf, put a 90° curve so it runs parallel to the drywall, run it a couple of fee then put another 90° curve so it can go through the other leaf. Then cut out a section in the middle, an inch or so long, and wrap that gap with a trip of soft flexible rubber, to de-couple the conduit from both leaves. The wiring itself won't flank much. When you have it wired, stuff a small piece of insulation into each end of the conduit, then put a db of caulk over that, to seal it. The key to good isolation is to seal EVERYTHING! Both leaves must be totally air tight. Is there something equivalent I should be doing with the ventilation ducts? I am assuming that these silencer boxes will be located between my inner and outer rooms...and physically attached to the inside of the outer wall? The fan could be inside too - but I imagine it will be easier...and smarter from a maintenance persepctive, to locate the fan on the outside of the outer wall...in an adjacent room - where I can get at it if it fails! But at the point where the duct (solid or flexible) meets the inner room wall, it will have to be fixed in place? 3. Just an aside - just in case there are any Aussies reading this fab forum - do you know a good place to get the lining duct for ventilation boxes that is mentioned widely on this site - is it a plumbing supplier? And what about those backing rods used when beefing up walls - any suggestions on suppliers down under? Thank you once again

1. Looking at the pic below (which is a relatively small build) - I am still finding it hard to see how, having created lets say 5 layers of plasterboard in two leaves...with not a single air gap - to mimimise sound transfer from inside the inner room - to outside the outer room....if I then build two air ducts (albeit with a couple of twists and turns for the air) that are 6" or so across - then surely I am going to massively undermine my sound isolation?? Or am I missing an obvious bit of physics here??

There are several things going on in a silencer that all help, but maybe the easiest way to think of it is like this: sound waves like to travel in more-or-less straight lines: air can move around corners. So the sound waves coming in the entry port immediately run into a damped barrier, right in front of them. That attenuates them a bit, but they do reflect somewhat, and partly "bounce" around the corner.... where they hit another damped barrier. Etc. Repeat, many times over. OK, so that's rather simplified, but it helps to give you a mental picture. There are also things going on, like like impedance mismatch due to the sudden changes in air volume and speed, energy lost in diffraction around the barrier edges, long path through the absorption due the glancing angels of incidence on the side walls, etc. The overall result is quite effective. Ever noticed how the entrance passage to modern movie houses starts with a door followed by a right angle turn, and the passage is lined with carpet over absorption? Same principle. Listen as you go in, next time, to how effective just a single 90° turn is.... :)

I am assuming that these silencer boxes will be located between my inner and outer rooms...and physically attached to the inside of the outer wall? The fan could be inside too - but I imagine it will be easier...and smarter from a maintenance persepctive, to locate the fan on the outside of the outer wall...in an adjacent room - where I can get at it if it fails! But at the point where the duct (solid or flexible) meets the inner room wall, it will have to be fixed in place?

You can put them anywhere they will fit! But the best place is to keep them outside of the isolation walls, if possible. Just like normal HVAC ducts, they might need cleaning / maintenance eventually, so it would be good to have them in accessible locations, in case you need to open them up. For example, if a piece of duct liner comes loose and blocks the air flow you don't want to have to destroy your MSM walls to get to it! Depending on your design, there are many options for positioning. And yes, you use the same approach as for the electrical conduit: decouple the ducts where they pass through the walls, with flexible couplings. Regarding the fans: Get ones that are really, really quite, and move a large volume of air at low speed, not a small volume at high speed. - Stuart -

Ya know what Pete, we can talk about this forever...and many of us here do. But the main thing that you as the GENERAL CONTRACTOR of this build has to do is to get passed the myths and into the facts. You came here with the well known 3 leaf, the scariest thing in acoustics according to Google, that could be imagined, but you have no basic construction experience and obviously no experience outside of that field that leans towards acoustics as it applies to a structure. Granted Stuart is far better in want or ability of typing accurate answers, and me I would want that the poster takes some time to learn what is the most difficult thing they are about to do in their life...which is to learn seven trades and the craft they do...and then to pile on top of that the acoustic design of a room...and I would try to point them in that direction. This is not a crash course and based on what I am seeing, it is the same thing we have seen for years where we try to get you up to speed because you (being any poster from any country over many years) does not want to get educated...they just want to DO:) Stuart thinks you are in a basement, I thought you were in an elevated wooded structure, but we find that you are in a coupled brick structure...this matters. We need more information then you think. So you have to get passed whatever Internet crap you think you know, and recognize that you know nothing and we cannot help you until you stop bringing junk into our life and look at this exactly like it is as if you are building a very complicated structure that you have no idea about how to go about it. Simple as that :)

Thanks Stuart. That's great. (Brien - not sure how I've offended you in my use of this forum. I am simply trying to make sure that, having built a room with pretty mediocre soundproofing first time...that I do a better job second time round. Sure it's not going to be the best sound room in the world...but I'm pretty confident that it's going to be at least twice as good as what's there right now (and about to be torn down)....and I am grateful...particularly to Stuart for that. Perhaps, if you are tired of newbies coming on and going through what is to you, a very basic learning curve, it might be a good idea to have a separate newbies section...in that way, good folk like Stuart who are happy (thank you STUART!) to repeat themselves :) can keep a watchful eye on us less experienced folk, and people like you, who are more interested in helping people rather further down the track with their 7 trades/ acoustic design experience etc, won't need to read the 70th/71st etc post on why a sound baffle works in the first place! The true magic and value of a forum is that it DOES fast track people like me, because, like having a teacher in a class room, it points you towards the questions you should be asking as well as helping you answer them. So the best thing is to structure the forum so that both the moderators and non-associated partipants all derive value (and even pleasure) from the experience!)

You have not offended me Peter...you are confusing me...big difference. I work day after day in the construction industry and we have meetings and prints and upgrades and cost negotiations and all manner of things with the various trades. I recognise that Stuart makes it easy for you guys, he is good at that, and you get your answers to easy and complex questions. This is not my strong suit. My strong suit is to help people (off-line) to understand the intrinsic details and the potential overwhelming possibilities that pretty much any type of project we are involved in can and will bring. And I do this by keeping them focused. If the questions get too far down stream, then I refocus to the here and now...past what is not a concern yet...like the three leaf issue. Fact is you cannot throw a dead cat in your house with out hitting a three leaf...so they exist you just were not aware of it. I understand the A.D.D. that comes with the Internet...the want for immediate gratification with the least possible work involved. I do not subscribe to this, and I want people to work to understand why it is, what it is, and how it is this project will get completed. You as a project builder will have hundreds of questions about all the trades techniques involved and how do you get them either up to speed or select someone that knows what to do in this environment. Stuart, how long ago was it that you did not know the difference between sheetrock and gypsum board? Not that long ago was it.... But he worked and now he has a celebrity status here at JohnSayers forum. So, it can be done Peter, and in the end, you are going to get an education like you never have before...but you have to be focused, and I think you lack it currently, and you have to get educated, ditto. Outside of that, I usually let Stuart and Glenn handle all this stuff...it cuts into my video poker time :)

(Thanks Brien....) Hi again..... I guess this is the key post now...as I am well and truly commited to the revised structure of a room within a room, so please..if you have time, have a look at my pictures and questions. If ANYTHING needs clarification, please do ask! The next step is beefing up my outer leaf... So here we have the stripped room. (A horrible job at the best of times - but oh so much worse when you only finished building it 2 weeks ago!) (Please see picture 'stripped room 4 walls') Wall 4 - the brick, single layer outer wall Wall 1 - the wall that's got retaining wall (and soil behind it) to about half way..and then some brick pillars that have a big beam across the top (that supports the joists). At this stage you can see voids - cupboards-to-be - that I created in the space above the retaining wall. More on these later. Wall 2 - the standard room-to-room structure - a single set of framing with gyprock on each side (near side now removed of course!) Wall 3 - like wall 2 - this has the door on it...and a window...more on that later too. (Please ignore all insulating material - mostly wrecked in the strip out!) From the conversations we've had thus far, I am pretty clear on what to do with walls 2 and 3. I'll pull out the insulation and fill the gaps between the framing with 16mm plasterboard to 'beef it up'. I'm also pretty clear what to do with the ceiling - basically as per walls 2 and 3 with a soffit around the heating duct. And electrics will be kept really simple - one power cable in..isolated...nothing through the ceiling etc. And air silencers as discussed.... But I have serious questions about beefing up walls 4 and 1. Starting with 4 (see picture 'wall 4 detail') - this single brick veneer wall has two areas where the brick depth is doubled - once at each end. My builder originally just framed across this so there is effectively a one-brick-deep gap between his timber framing and the wall. Am I right to think that I should just pull out this frame and add plasterboard directly to the wall - building it up between the two double-brick-thickness areas. I doubt I'll get all the way - even with three layers of plasterboard - but I'll certainly add mass! The bricks are the hollow ones....pretty lightweight.) Or do I also need to add plasterboard in front of the double thickness bricks to maximise isolation? (This means the wall will not end up with a single plane of plasterboard...and going in front of those double bricks with plasterboard will also reduce space in the room a little....but if I need to do it...so be it! (I've seen mention of cement/render on brick..is this better than plasterboard for this outer leaf..is this better?) Then wall 1 - the hardest of them. (see picture 'wall 1 detail). This wall has a 12" deep plus retaining wall of concrete blocks and solid mud behind it up to a height of 1m 19 off the ground. Above this retaining wall, from left to right are... The brick wall at the side of the house (between me and the neighbours) - wall 4 More concrete (part of the slab - the house is on a steep hill) and void A above it This is currently separated from Void B/C by a timber partition created by me as storage - NB void B and C are one large space - broken only by the brick pillar at the front - pillar supports beam supporting joists) Then another brick pillar and the Void D - which I have paritioned off as storage space accessed from the next door room. Then we're at wall 2. Two issues on this wall....do I attach plasterboard to the front of the concrete wall (I don't imagine I can improve on its 'mass' much!! - but maybe there's a consideration about having a solid sheet top to bottom) And assuming the advice from the next para is just to block off the voids above....do I 'beef' between the brick or over it? (....I obviously need all my plasterboard beefing on this wall to be one solid mass!! The front of those brick pillars are on the same plane as the concrete retaining wall....(or do I brick up the gaps and render over everything..the possibilities are many I think!) Second issue on this wall - before I was thinking of rooms within rooms...I created the B/C void to put speakers in - thinking of having my keyboards set up on wall 1 - the B/C void giving me a chance to 'bury' my speakers and not lose space in the room. However, now that I am building a room within a room it is MUCH too hard to think of getting my speakers in there - even if I could build it - the speakers are just too big. So - should I keep things simple and close it ALL off.......NB If I close it off altogether I assume I will have to open it at the back to avoid the triple leaf effect - which is a shame to lose the storage space...but sound isolation is the most important thing! I COULD use the space for my air silencers...or if someone were to tell me that a 'box in the wall' (just in void C) off my sound room will improve the acoustics I could just create storage space in there by 'hanging' a box in space in that void off the room in the room. (Forgive the mention of speakers and keyboards - the trombone is still the focus - but I do want my composing stuff down there too!) Finally - going back to wall 3 - the original room had a window with two layers of glass bricks...I assume I should just take these out and plasterboard over....the light was pretty meagre..and sound isolation is the main aim! I do have a thought on the entry point too - reading all this stuff about sound travelling in straight lines and people staggering their plasterboard corners etc - I thought I'd build my inner and outer room doors slightly offset from one another....so the verticals don't overlap...and then perhaps a small step on the inner door...what do you think? Sorry once again it's such a long post. Your help and guidance would be greatly appreciated! P PS A couple of new measurements. Wall 4 (from the double brick part on the ends of the wall) - to the nearside of the framing on wall 2 - 2460mm Wall 1 (from the concrete wall) to nearside of framing on wall 3 - 2050mm Height floor (no flooring) to joist 2570mm

Hi again... I'm wondering if that last post had too much in it to respond to... So, just looking at wall - four - a single brick veneer wall...to beef it up do I a) affix plasterboard, b) render or c) build a second layer of bricks (the ones that are there are the hollow ones - if I build a second layer - I'll use heavier/ solid ones if I can! And looking at wall - one - to beef it up - do I just fill the gaps between the brick piers (above the retaining wall) with more bricks - or do I plasterboard over the voids (and over the bricks and.... over the retaining wall)? Thanks so much Peter

The first thing that I immediately notice is the reduced head room...it is already so low that any reduction can not be helpful musically speaking. A few other observations based on basic building design. A typical brick wall has brick ties that connect the wood framing to the brick creating a path for vibration to ride on. This is a coupled wall assembly. Block works the same way. So can you answer that question Peter? Does the existing framing have a hard connection tied into the brick and/or block? If it does not then I would submit to you that beefing up a brick or concrete wall that seems to be already damped by the exterior earth wouldn't be my point of focus. Also you mentioned concrete block and if painting it would make it an improved barrier. If it is (the concrete block) is part of the interior thermal envelope, then yes, painting it can reduce some of the ability of this porous material to become more solid. If it is part of the exterior thermal environment, then IF it is to be included as part of a mass/spring/mass framing (room-in-a-room) then no I would not do it. As it stands or looks at this moment in time, if you have framing that is not connected in any way to the exterior brick and block, then you have a fully decoupled wall framing. Now the issue is the low ceiling that is certainly coupled to the interior. In this instance you would want to mass up the upper floor area as much as required, insulate and use RC to make the decoupling. In any event, you do not want to tear out framing if you have defined that it is connected to the exterior brick...OR supports the overhead ceiling...this would not be a good thing for you.

Thanks so much for getting back to me...I thought I'd respond to your comments in turn... With one over-rider.... that framing you see in the pictures is only 2 months old and plays NO part in the structure of the original house... the joists that support my house (that run front to back) are supported by a beam on top of the brick pillars you can see above the retaining wall...and on another beam across the front of the house...

xSpace wrote:

The first thing that I immediately notice is the reduced head room...it is already so low that any reduction can not be helpful musically speaking..

Indeed at 2570 to the joists I'm not going to be able to make a 2.4m ceiling work - for this reason I AM going to do away with that air duct so that there's no soffit extending down any lower than the current joists...by my calculation this means if I have a 5 mm gap, plus 135mm joists (on the room within the room) with three layers of 16mm plasterboard (48mm) gives me 188mm off the 2570...plus 10mm for the floor - I get a ceiling height of 2372....which is 28mm below the standard...(or within it - depending on how the room is classified - as a 2.1 or a 2.4!). The only way I can get to the 2.4m standard is to use smaller joists on my inner room (and have more of them...) - the span is only going to be 1.6/1.7m...so the usual 90mm framing is probably enough to support my ceiling..plus lots of 90mm will give me plenty of timber to screw my plasterboard to. (I know I can also interleave the inner room joists - but this means cutting into the blocks between the joists and I am a little nervous of doing this!)

xSpace wrote:

A few other observations based on basic building design. A typical brick wall has brick ties that connect the wood framing to the brick creating a path for vibration to ride on. This is a coupled wall assembly. Block works the same way. So can you answer that question Peter? Does the existing framing have a hard connection tied into the brick and/or block? If it does not then I would submit to you that beefing up a brick or concrete wall that seems to be already damped by the exterior earth wouldn't be my point of focus...

The way that the timber framing has been done (NB this framing you can see was only built a few weeks ago and is NOT part of the structure of the house) is as follows - it TOUCHES - but is not screwed to the brick wall of wall 4. And it TOUCHES but is not screwed to the retaining wall/ brick pillars at the back on wall 1. It is nailed to the joists at wall 1 and wall 4. (And it is screwed to the floor - I am sure - though I cannot see the screws I presume they are under the vertical timbers.) By my understanding this means that it IS coupled...which is what I assumed when I pulled down all the plasterboard. Hence my plan to just rip it out on walls 4 and 1. But this is a crucial bit for me - what I have on wall 4 is a single brick veneer wall that sits on my slab. And what I have on wall 1 is a concrete retaining wall (to 1.2m) sitting on the slab..and then some brick piers going up from there (with VOIDS in between) that support beams/joists above (NB NONE OF THE TIMBER WORK THAT SUPPORTS MY HOUSE, OTHER THAN THE JOISTS IS VISIBLE IN THE MUSIC ROOM). I would really appreciate your thoughts on: a) whether I will get benefit by doubling of the brick mass on the external wall (wall 4) - or by increasing its mass by rendering.....(or whether I should just make it air tight and move on!!) and b) whether filling the voids between the brick pillars on the retaining wall...with bricks - as opposed to covering the whole area with plasterboard - is the way to go! NB both these walls will be OUTER leaves in my final room-within-room structure.

xSpace wrote:

Also you mentioned concrete block and if painting it would make it an improved barrier. If it is (the concrete block) is part of the interior thermal envelope, then yes, painting it can reduce some of the ability of this porous material to become more solid. If it is part of the exterior thermal environment, then IF it is to be included as part of a mass/spring/mass framing (room-in-a-room) then no I would not do it....

Thanks for this - but I'm not sure about the painting thing..that may have been someone else...I was actually wondering if RENDERING was a better alternative to a second layer of bricks on wall 1....see above....

xSpace wrote:

As it stands or looks at this moment in time, if you have framing that is not connected in any way to the exterior brick and block, then you have a fully decoupled wall framing.....

The fact that it is touching the brick (wall 4) and the concrete blocks/brick pillars (wall 1) I presume means that it is in fact 'coupled'??? Even if there are no screws connecting them???

xSpace wrote:

Now the issue is the low ceiling that is certainly coupled to the interior. In this instance you would want to mass up the upper floor area as much as required, insulate and use RC to make the decoupling......

That's the plan - except I'm going for a room within a room rather than decoupling with RC as I am more confident that I can make it work!

xSpace wrote:

In any event, you do not want to tear out framing if you have defined that it is connected to the exterior brick...OR supports the overhead ceiling...this would not be a good thing for you.

Are you saying this because you are concerned about me impacting the structure of the house?? I imagine you are - hence my stressing that none of this framing formed part of the fabric of the house as it was only put in very recently as part of this reno. So I am quite happy to pull down the framing that was put up for walls 4 and 1... indeed I imagine I will be able to reuse it in my inner room. PLUS...in actual fact, the framing for wall 3 - which IS nailed to the joists and IS new...and IS staying in place as the outer leaf in my new build...is in fact creating a support for my main house joists that was NOT there before...which is what gives me the confidence that I can indeed add this 'beefing' mass in between the main house joists without straining the structure as the joists now have their span cut almost in half. Thanks again for taking the time to help me....I'd be VERY grateful for your specific thoughts on my questions in red. Best Peter

by my calculation this means if I have a 5 mm gap, plus 135mm joists (on the room within the room) with three layers of 16mm plasterboard (48mm) gives me 188mm off the 2570...plus 10mm for the floor - I get a ceiling height of 2372....which is 28mm below the standard...(or within it - depending on how the room is classified - as a 2.1 or a 2.4!). The only way I can get to the 2.4m standard is to use smaller joists on my inner room (and have more of them...) -

... Or you could build your ceiling "inside out", and lose less height, since all your treatment (or most of it) could then go in between the joists... :) Or you could interleave the new joists between the old, thus losing only a 5 or 6 cm... :) Lots of ways of skinning a cat!

so the usual 90mm framing is probably enough to support my ceiling..

"probably" ain't very smart! :) "Probably" won't pay your medical and insurance bills if something breaks! :) What is smart is to find out for sure, by checking span tables, checking your local building code, and best of all, getting a structural engineer involved.

(I know I can also interleave the inner room joists - but this means cutting into the blocks between the joists and I am a little nervous of doing this!)

You don't necessarily have to cut them: you might be able to replace them with diagonal cross bracing. A lot of work, but it might be worthwhile to gain those extra few cm, if height is an issue. But once again, don't go cutting or replacing anything without getting the opinion of a qualified structural engineer. That's my $0.02, but you should listen to Brien here: he's the construction guy around here! - Stuart -

"I would really appreciate your thoughts on: a) whether I will get benefit by doubling of the brick mass on the external wall (wall 4) - or by increasing its mass by rendering.....(or whether I should just make it air tight and move on!!) and b) whether filling the voids between the brick pillars on the retaining wall...with bricks - as opposed to covering the whole area with plasterboard - is the way to go!" I would render it...anything that will reduce the flow of air or penetration of moisture, do that. Here is the overall view from where I seat. In theory, a mass/spring/mass wants to have the same amount of contiguous mass on the exterior leaf all the way around. Ditto on the interior side. Granted the exterior can be of a different material since it is assumed it will be of an exterior assembly grade...so it is what it is. So your current situation presents some issues that may not be worth trying to achieve in this goal. The weakest link in your isolation is the overhead floor...it is not even close to the exterior bricks ability to isolate sound. So I have to wonder aloud here, two things. Was this a purpose built room that failed in the goal of isolation, and if yes is the answer, are we still moving too fast? But that's just me...it is after all your time and your money. But beyond that, close up the brick walls ability for air to penetrate it, render it, caulk it, etc. If you are certain for a fact that this framing is in no way part of the original structure and that it can be removed safely with no failure to the structure, then remove it with care, as you will want to use it again. You final goal in the extraction of the interior wooden framed walls is to get them off of the brick, break that connection no matter how small it might be. Then you want to move the framing away from the brick, get an air gap between the brick and the framing. Forget ratios...they are not in your future.:) The only thing that you can do at this point is to not frame up anything that has a multiple of the other dimensions. Like that 6 foot tall ceiling, if you make a wall 12 feet, then you have just violated the recording space since whatever modes the 6 foot tall ceiling will produce, the 12 foot long wall will only re-enforce. Don't forget to get some air in that place via HVAC. A larger room might be more forgiving, but a small room will >require< that you can breath as a human...and it will want more air since the volume is compromised so you are directly breathing in what you just breathed out.

Thank you Brien - that's REALLY helpful. I'll render wall 4 - the brick wall. And fear not! There is a ventilation system planned... May I ask - just on that wall 1 - where I have brick pillars on the retaining wall - with big gaps in between - would you plasterboard between these/over these...or brick up the gaps and render over the top?I presume there's no need to touch the retaining wall as it has solid earth behind it! Yes - this room was an attempt by my builder at building me a practice room - but the fact that everything was coupled - including the ceiling meant that noise transfer was just too great. And because of how it was done - the three leaf effect required a strip/rebuild..not just an 'add more'. And as you say - the worst place was directly overhead - in our living room. Alas the builder was not a sound expert and just put up extra plasterboard..and I was too focused on building bedrooms for the baby etc to do my research! I have now reorganised everything so that I can make the space we need before the baby is born late Feb....and finish the music room at whatever pace is necessary! (Thank you for the comment on internal dimensions too - noted!) And thanks to you too Stuart - I have asked an engineer to confirm the spacings I need between my bearers on the inner room to support 3 layers of 16mm plasterboard! LATE NEWS - I have my answer from the engineer: 90*45 mgp10 rafters (ceiling joists) at 450 centres carrying 40kg/m2 can span 2600mm - so I can use 90x 45s (the Aussie 'equivalent' to a 2x4) for the bearers and I'll keep my 2.4 head room....yeay! Though I might put the centres at 300 so a) Ive got more to screw to and b) if I need a 4th layer of plasterboard, I have the carrying power above!!

peter1908 wrote:

May I ask - just on that wall 1 - where I have brick pillars on the retaining wall - with big gaps in between - would you plasterboard between these/over these...or brick up the gaps and render over the top?I presume there's no need to touch the retaining wall as it has solid earth behind it!

I would backer rod the joint and use a high quality caulk aimed at concrete or weather-proofing brick or morter or concrete. But I would have to see the joint first.

peter1908 wrote:

Yes - this room was an attempt by my builder at building me a practice room - but the fact that everything was coupled - including the ceiling meant that noise transfer was just too great. And because of how it was done - the three leaf effect required a strip/rebuild..not just an 'add more'.

A three leaf requires multiple air spaces...like two air spaces to be a 3 leaf. It takes a mass/an air space/ a mass/ an air space/ and a final air space mass with no hard connection between any of the air spaces or the mass...or then it becomes a couple assembly

peter1908 wrote:

And as you say - the worst place was directly overhead - in our living room. Alas the builder was not a sound expert and just put up extra plasterboard.

Well, adding mass directly to the underside of the upper floor assembly is part of the project. And will always be the weakest link so you have to treat it like a wall assembly that just happens to be over your head horizontally.

peter1908 wrote:

LATE NEWS - I have my answer from the engineer: 90*45 mgp10 rafters (ceiling joists)

A 2X4 for such a small span could have been resolved right here, had I known what the span, the outside dimensions of the wall to wall assemblies would be, were. What did that engineer cost you? But the layout is 406mm centers not 460mm and reducing it will gain you nothing.

Hi Brien - and thank you. Here's a pic of one of the voids I'm talking about - I'm assuming that I should brick them up as all your comments thus far have indicated that brick is a pretty good sound insulator. It may be a bit tricky in a couple of places - but if I get as good a fill as I can with the bricks and then fill any gaps/joins with a good caulk/ backing rods, I presume that would be better than just using plasterboard? (And don't worry about that engineer advice - it was free! So I'm very glad you're happy with the numbers too!) All the best. P

Instead of bricking the voids up, why not use them as deep bass traps, or absorbers? Perhaps they need a lining of drywall inside ans on the ceiling to realize this.

Thanks Brien - You suggested not just bricking OVER the voids but on using the space as bass absorbers... And then mentioned using drywall etc. Can I just check this.... You are suggesting essentially creating a 'box' in the wall of the outer leaf (with plasterboard) And then this will mean having a smaller 'box' in the wall of the inner leaf that 'hangs' in that outer leaf box. Pls see my picture... If I have this correct....may I ask a) what kind of size the box in the wall of the inner leaf should be... b) Whether I should create one or two (assuming there is room for two at the size you suggest c) whether the 'box' in the outer wall should be made of brick wall/ drywall ceiling (to leverage brick's superior ability to stop sound travelling into the house) or all drywall. Remembering my principal goal is to practise the trombone down there without the sound carrying into the house/ over to the neighbours! Thanks again Brien. Your guidance is very much appreciated! P