NEW PROJECT - Purpose built outbuilding

[AlunH]

Hello!

This is my first post to this forum, even though I have been following many threads over the years. After reading and re reading the rules, I think it is about time to take the plunge on a project. So here goes. I have tried to break this down and section things off as much as possible, with questions at the end. I have a tendency to ramble so i apologise in advance!


BACKGROUND:
I used to co-own a recording studio (pink house studios), designed and built for me by Peter Keeling of StudioPeople back in 1996 [...] The studio was used predominantly for our own productions and remix work and for other artists for whom we released product on our independent dance music label. Times changed, people stopped buying vinyl and CDs and the work dried up. That was back in 2004, but i kept a small collection of synths and outboard. The old studio by the way, was taken over by Arthur “Artwork” Smith So is still being used and is there if i ever need it for a final mix down.

GOALS:

After many years retraining and carving out an alternative career, I am in now in the fortunate position to build from scratch a purpose built outbuilding “incidental to the enjoyment of the main dwelling house” as the local planning department (Bexley Council, South East London) would describe it. The development will be located approximately 45 metres from the house and any other neighbours. It needs to be multifunctional; providing a small office area, some sofa’s for evening relaxing / dining and as a music writing / sound designing /mixdown for my own private electronic compositions.

I am not looking to get the same levels of isolation or acoustic perfection which I previously enjoyed but I do want a workspace which will have the minimum of room nodes to be able to mix and perhaps master with reasonable results. I am hoping that having a green field site will help with 90% of that battle.

SIZE:
The maximum floor area for the building will be 30m2. Any larger and I will have to have building regulations inspectors involved and costs will start to spiral.
Local planning - Recent changes in legislation allows a domestic property owner to build a “Permitted Development” without planning permission as long as i) it is no higher than 2.5m (max height) if it is nearer than 2m to the property boundary. ii) it is no higher than 4m in the case of a pitched roof with an eaves height no higher than 2.5m or iii) it is no higher than 3m in any other case In real terms this means that if it has a flat or tilted roof it can be no higher than 2.5m to the eaves an no higher than 3m total and must be further than 2m from the boundary. See PLANNING: (below)

BUDGET:
My total budget is about £15,000 I do have a little wiggle room up to to perhaps £18,000 but i’d like to save where i can to buy a mixing desk and control surface.

SITE: The back garden is a rectangle about 50m long and 10m wide. The building will be 45 metres from any other buildings. Soil type (according to the UKSO.org) appears to be freely draining slightly acid loamy soil. There is some clay and I have yet to determine how deep the water table is. The erection will be built in the far corner of our curtilage against the boundary with one of our neighbours and some scrub land which forms part of some local allotments. It will be built in the same place as a 2.5m x 7m shed (2.7m high) which was rotten and I recently dismantled.

PLANNING: We want to position the building in such a way that it benefits from windows to a south west facing aspect from late autumn to early spring but incorporates an overhanging roof to provide shade form the summer sun. This will help the building be more economical to heat and cool and be less impactful on the environment. Given that i am 6” 6’, it will be difficult for me to design a “Permitted Development” which is thermally efficient, allows enough space for sound proofing whilst having high enough ceilings for me to actually stand up. Therefore, I will be looking to apply for planning permission but want to keep the building as low as possible in order to make it more likely to get the permission to build but also so that the building isn’t an eyesore for my neighbours. They are nice people on both sides and we all get on very well.

MONITORS:

NEAR FEILD: I have a pair of Yamaha NS10ms which i plan to use as near field monitors mounted on desk which will house a small control surface for LOGIC PRO X,16 ch mixer, master keyboard and some essential rack kit I/O etc.

MAIN: I Have a pair of Tannoy System 800 and a QUAD 405 which work nicely together and I know quite well. I would like to soffit mount these and perhaps have a slate / rock tiled (slightly diffuse) front wall, perhaps with a central window to look out onto the garden and introduce natural light.

OTHER KIT: I have a couple of old drum machines a Korg M1, Roland JX10, moog SUB37 and some rack synths, samplers, e.q., fx units etc. which will live at the far end. I would like this area to be slightly more ‘live’ to get a better impression of reverb when jamming /sound designing, if possible.

SO FAR:
I have been lurking here on these forums for years and joined up in December ’16. My background is in building engineering services and then taught myself sound engineering by reading books and then attending a btec diploma course in 1994. I understand the basics of building construction, thermal coefficients, sound transfer coefficients, why room ratios matter, how sound travels, measuring sound pressure levels, the basic principles of using mass to absorb sound and how reflections can create cancelations and peaks in certain frequencies dependant on distances. I am aware that small rooms are most challenging at lower frequencies. I have read about not floating a floor unless you have lots of mass and even more money. However, I don’t profess to understand the differences between axial, oblique or tangental modes or how to use the outputs from amroc to help design or alter a room for the better. THAT”S WHERE YOU GUYS COME IN… I HOPE!

I have downloaded and started watching Sketchup “How To” video’s and have access to a decent Wacom tablet. I will be creating the drawings for the build myself and calculating the loads and designs from online resources. Im nearly 50 years old now and have the typical tall person (6’6”) issues of minor back problems. But I can manage operating a compactor plate, power drill, table saw etc. and will probably attempt most of the internal stud wall construction, electrical wiring and HVAC work myself. I have never laid a brick in my life but have repointed a couple of walls to a medium level of satisfaction.

MY INITIAL THOUGHTS ON CONSTRUCTION ARE…..

FOUNDATIONS & EXTERIOR WALLS; Dig (hire a mini digger and driver) 750mm to 1m deep trench for a concrete foundation. Build up to the DPC level (hire a bricklayer) with 100mm thick concrete blocks. In fill with ballast and sand and then tamp down. Lay the DPC then build the walls up in the same 100mm thick concrete block to create the outer walls of the building. The inner floor would then be poured (over a reinforcement grid) onto the DPM. Exterior finish would be 1” battens with painted timber clad to give it a more pleasing wooden shed appearance perhaps something like this.

THE ROOF: (I haven’t decided on warm or cold roof yet) To keep it simple (i don’t know how to design roof trusses) it will likely be a mono pitched (tilted slab) affair made from timber joists infilled with insulation with a roofing deck on top, an EPDM cover or perhaps a living sedum roof if the budget allows. Advice hear would be nice.

INTERNAL WALLS: Will be timber frame 4 x 2 stud infilled with 4 inch insulation slab and a 2 inch (50mm) air gap between the internal and external wall. I was thinking of covering the inside of the internal wall with 2 layers of plasterboard but was unclear whether i should mount that to the stud wall frames using resilient bars. I will (if it is advisable) build the walls to be mounted on rubber pucks direct onto the concrete floor. Once the stud walls are built (but before the plasterboard goes on) I would then build a 4 x 2 frame for the floor (also on pucks) isolated from the walls. I would then lay an OCB floor up to (but not touching) the timber stud walls and then apply the first layer of plasterboard against a perimeter bead of acoustic caulk on the OCB floor. Then lay a second OCB layer on the floor (acoustic caulk bead between it and the plasterboard) and then finish with the final layer plasterboard again laid onto a perimeter bead of caulk on the final OCB floor layer. This way there will be a staggered air seal but no physical connection between the floor raft and the walls. IS THIS METHOD OK?

ACOUSTICS: I am looking to have a rectangular room with ratios from the bolt /louden areas. (1:1.42:162 looks good) Then treat where needed: wide band absorbent cloud above the CLP, Absorbent side wall coverings to eliminate 1st reflections, diffused rear wall, bass traps in corners.

HVAC: I intended to build an inlet and outlet baffle box with a simple fan to introduce fresh and expel stale air. I will also add a cheap(ish) sealed split system around 2.5kw. It rarely gets above 30 degrees C (86F) in the this part of the UK (maybe 5 to 10 days of the year) and only drops below freezing a few times a year.


LAYOUT: I am exploring two different avenues.

1 - Create two separate rooms. One for music, the other as the office /garden room:

ADVANTAGES:

Security: for my synths and other equipment (thieves would need to get into the building and then through two other doors to get into the studio)

Isolation: The wife would like large windows (perhaps bifolds) to open out to the rest of the garden /barbecue area. Having the music room separate from the garden room will reduce costs of double bifold doors and the inherent reflective surface they would introduce.

DISADVANTAGES:
Room Size: With only 30m2 to play with, the music room will be of dimensions which are not ideal. The distance between the CLP and side walls will be too small to use diffusion. Room nodes will be more disruptive and need more treatment to stop the room ringing at many different frequencies.

This option would be a 1:1.42:1.67 music room (2.3m(H) x 3.27m(W) x 3.84m(L) The office /garden room could be the same size or slightly smaller such that the building is a kind of fat L shape.

2 - Have one large multifunctional room

ADVANTAGES:
Acoustics: larger listening space and therefore fewer room nodes. Ability to introduce diffusion on side walls. Potential room size 2.1m (H) x 4.54(W) x 6.22m(L) = 1:2.16:2.96

DISADVANTAGES:

Isolation: No separation between music kit and garden room.
Security: Decreased security /safety for valuable kit.


CONCERNS: I’ve entered the above sets of dimensions into amroc and been very scared by the results. Unless you are able to reduce RT60 down to like 0.2 seconds, these dimensions all look to be really bad! It looks like you need a room the size of wembley stadium before room modes are no longer a problem. Yet I have worked in many small studios 3m x 4m x 5m.. ish, which all sounded fine after a little bit of treatment. Am i getting overly worried about the room mode calculator?

QUESTIONS:

Which layout do i choose? - 1 or two rooms. thoughts on costs, security and acoustics please.

When using room ratios and measurements, should I measure the internal dimensions from face to face or should i go by the internal sides of the heavier outer walls, floors and ceilings?

Which type of roof - warm or cold, pitched, monopitched or flat? This may have a bearing on potential room height.

How high should I go? What is the optimum ceiling height for a small control room.

Is there an ideal room ratio for rooms under 100m3, and should I aim for that?


Regarding Ceiling height - I want the best sound but don’t want to piss off the neighbours or run the risk of not getting planning permission. Anyone with similar suburban UK experience that can share their experiences would be most welcome.



Once I have some answers to the above, I will start to create a Sketchup document of the layout and then add detail for wall sections, Wall to floor sections, wall to ceiling etc. and then perhaps start to look further into details such as spacing and type of rubber pucks to support the inner walls & floors, how do I suspend the ceiling etc.

Please let me know if I have missed any important information or if there are any books which i should order and get my head around during this design stage. Your help and assistance will be very much appreciated.

Best regards,
Alun

[Soundman2020]

Hi there Alun, and Welcome!

Congrats on your project!

It needs to be multifunctional; providing a small office area, some sofa’s for evening relaxing / dining and as a music writing / sound designing /mixdown for my own private electronic compositions. ... The maximum floor area for the building will be 30m2. ... My total budget is about £15,000

The math and reality are not working out too well here, I'm afraid. You want a studio with at least three rooms, it seems: the actual control room, plus the office area, plus the dining area. The dining area cannot be inside the control room, for obvious reasons. I suppose you could combine dining and office, but it seems that 3 rooms would be best. But in only 30m2, that's not much space at all! Specs for control rooms call for a minimum of 20m2 if you want decent acoustics, which only leaves you 10m2 for the dining area and walls.... Then you are saying that you want to build 30m2 on a 15k budget, implying that you plan to spend just £ 500 per square meter. That's about half of the going rate for ground-up builds in the UK, according to the customers that I have designed places for. They tell me they spend around £ 1000 per m2, give or take a couple of hundred. So either you need to shrink your building down to 15m2, or you need to increase your budget.

Soil type (according to the UKSO.org) appears to be freely draining slightly acid loamy soil.

Great! Foundations won't be to complicated then. You can probably get by with a monolith slab on grade over a gravel bed. But don't take my word for it: You'll need to hire a structural engineer to check your design for that, once you complete it, along with the design for the rest of the building structure.

I am not looking to get the same levels of isolation or acoustic perfection which I previously enjoyed but I do want a workspace which will have the minimum of room nodes to be able to mix and perhaps master with reasonable results.

I think you meant to write "modes" not "nodes" there? But you seem to be understanding things backwards: you do not want to minimize the number of modes! You want to maximize them! If you could have a room with several modes for each note on the keyboard, you would have a wonderful room. The problems only happen when you don't have enough modes! When there are large gaps between modes, where some notes have no modes at all, where the few modes that are available are bunched up together at just a couple of notes, THATS when you have problems. Not because of too many modes, but because of too few.


We want to position the building in such a way that it benefits from windows to a south west facing aspect from late autumn to early spring but

incorporates an overhanging roof to provide shade form the summer sun. This will help the building be more economical to heat and cool and be less impactful on the environment

That isn't as much of an issue as you'd think, with a studio. For a typical house, yes, but studios are double-walled, double hermetically sealed, triple insulated, and there's not much you'd gain by trying to use passive heating and cooling. In addition, large windows are a large expense, and you don't have that luxury on your tight budget. In fact, you'll probably have to do it without any windows at all on that budget.

Given that i am 6” 6’, it will be difficult for me to design a “Permitted Development” which is thermally efficient, allows enough space for sound proofing whilst having high enough ceilings for me to actually stand up

I don't understand why! Maybe you can explain? Under Class E (which most back-yard studios in the UK use), your roof peak can be at 4m for a dual-pitched roof, as long as the building is not within 2m of the property boundary. Your eaves have to be less that 2.5m, but that's not a problem.

Why do you think that would be a problem? I'm in the final stages of designing a studio for a customer in the UK right now, and the ceiling height is coming in at 2.6m. That's 8'3", roughly. Higher than a typical house ceiling, by several inches.

Why do you think it will not be possible to get good isolation and decent ceiling height? I don't understand the problem.

Therefore, I will be looking to apply for planning permission

If you apply for planning permission, then you are not limited by size or height, .... until they tell you otherwise! You can present anything reasonable, and you stand a fairly good chance of getting it approved.

I have a pair of Yamaha NS10ms which i plan to use as near field monitors mounted on desk ...

First mistake: Monitors should NEVER by on the desk, or the console meter bridge, or the dog box. Yes, you see that all the time in pictures of studios, but that does not make it acoustically right. I see pictures all the time of people who should know better doing lots of strange things, but that does not make it right either.

The reason is very simple: If you put your speakers on the desk, you will have the following problems: Early-early sound (arriving at your ears before the direct sound), reflections from the desk/console surface, comb filtering from the desk/console surface, a boost in some frequencies in the lower mid range, due to proximity to the desk/console surface, uneven frequency response in the mid range, and a few other fun things too!

I Have a pair of Tannoy System 800 and a QUAD 405 which work nicely together and I know quite well. I would like to soffit mount these

Smart move! That can certainly be done, and will possibly even help to extend the low end a but better than the listed 47 Hz. Or you might want to consider adding a sub to get down into the lows.

and perhaps have a slate / rock tiled (slightly diffuse) front wall,

That's going to be expensive. You might want to reconsider that on your budget, and go with a more conventional soffit mount.

perhaps with a central window to look out onto the garden and introduce natural light.

Not a problem at all, acoustically, but it might be financially.

OTHER KIT: I have a couple of old drum machines a Korg M1, Roland JX10, moog SUB37 and some rack synths, samplers, e.q., fx units etc. which will live at the far end. I would like this area to be slightly more ‘live’ to get a better impression of reverb when jamming /sound designing, if possible.

Nope. Not possible if you want a room that has the necessary neutral acoustics required for a control room. Or rather, it's not possible on a tight budget. You would need to design, build and test variable acoustic devices that you can open/close/slide/flip/rotate/flip/etc. in order to change the acoustic response of the room from "neutral" to "live". It is possible, and I have done that for a few customers, but it's not so cheap. On your budget, it's probably not on the table.

the basic principles of using mass to absorb sound

Your understanding seems to be flawed here. Mass does not absorb sound. Mass reflects sound. You can absorb sound with porous materials, or by using resonance in various ways, but you can0t absorb it with mass.

I don’t profess to understand the differences between axial, oblique or tangental modes or how to use the outputs from amroc to help design or alter a room for the better. THAT”S WHERE YOU GUYS COME IN… I HOPE!

Dig (hire a mini digger and driver) 750mm to 1m deep trench for a concrete foundation. Build up to the DPC level (hire a bricklayer) with 100mm thick concrete blocks. In fill with ballast and sand and then tamp down ... The inner floor would then be poured (over a reinforcement grid) onto the DPM..

Personally, I think it would be easier, cheaper, simpler, and more effective to just do a simple monolithic slab on grade. As far as I know, there's no problem with that in the UK for a small Class E building such as this. It's one single pour, and it's done!

THE ROOF: (I haven’t decided on warm or cold roof yet) To keep it simple (i don’t know how to design roof trusses)

Then maybe you should learn, or hire someone who does?

it will likely be a mono pitched

With a Class E building, that limits your maximum height to 3m at the peak. Not a good idea if you need good headroom.

from timber joists infilled with insulation with a roofing deck on top, an EPDM cover or perhaps a living sedum roof if the budget allows.

If you want a green roof, you are going to need a much larger budget, and a structural engineer. Damp earth weighs around 1300 kg/m3, so a bed just 10cm thick, covering 40m2 (allowing for overhang), is going to weigh roughly 5 tons, plus the structure itself to support it, for a total of maybe 7 or 8 tons. DO you feel comfortable designing the structural support system for a roof that weighs as much as four or five small cars? And with all of that sitting right above your head?

Advice hear would be nice.

If you want good ceiling height, simple construction, and low cost, then just go with a standard gable roof.

INTERNAL WALLS: Will be timber frame 4 x 2 stud infilled with 4 inch insulation slab and a 2 inch (50mm) air gap between the internal and external wall.

Have you checked if that will give you enough isolation at the frequencies where you need it?

I was thinking of covering the inside of the internal wall with 2 layers of plasterboard but was unclear whether i should mount that to the stud wall frames using resilient bars.

Not necessary. Since your inner-leaf wall is already fully decoupled form the outer leaf, then you do not need RC (and that would be a heavy load on your budget anyway!). You would only need RC if your inner-leaf wall is attached to the outer-leaf at some point (apart from the floor).

I will (if it is advisable) build the walls to be mounted on rubber pucks direct onto the concrete floor.

Not necessary, a waste of money, and a bad idea if you don't know how to do the math to ensure that it floats.

I would then build a 4 x 2 frame for the floor (also on pucks) isolated from the walls.

Huh? Why on earth would you do that??? You are already short of head room, so why would you wast 5" or 6" of it unnecessarily? Have you read about how to float a floor successfully? Take a look here: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

You already have a perfectly good floor with your slab on grade. Why wreck that?

I would then lay an OCB floor

I'm not familiar with that type of flooring. Is that something you get in the UK? It must be a very recent thing, as I can't find any references at all for it on Google.

I am looking to have a rectangular room with ratios from the bolt /louden areas. (1:1.42:162 looks good)

I think you mean " 1 : 1.42 : 1.62". If you made "it 1:1.42:162", you'd need to by a few more lots of land to fit it all in!

But yes, that's a decent ratio.

wide band absorbent cloud above the CLP,

CLP??? "Clinical Lab Products"? "Chilean Peso" (I'm somewhat familiar with that one!)?, Certified Linux Professional? Color Laser Printer? Command Line Processor? Communist Labor Party? City of London Police? Chlorine Loading Potential? Customer Loyalty Program? I'm using an acronym finder, but not coming up with anything that seems related to sound or construction materials...

Absorbent side wall coverings to eliminate 1st reflections,

You cannot eliminate first reflections with wall coverings.

... wide band absorbent cloud above the CLP, Absorbent side wall coverings to eliminate 1st reflections, diffused rear wall, bass traps in corners. ...

All of the above combined with the soffit mount, leads me to suspect that you are trying to do an RFZ design here. Is that the case? Or did you have something else in mind?

I intended to build an inlet and outlet baffle box with a simple fan to introduce fresh and expel stale air.

Great, but you seem to be aiming for high isolation with everything you have described so far, which implies that you will need high isolation in your HVAC system too. That in turn implies that you will need four silencer boxes: two on the supply side, and two on the exhaust side. (one on each leaf on each side).

I will also add a cheap(ish) sealed split system around 2.5kw.

That sounds about right (roughly 8,000 BTU/Hr, but you'll need to do the math to be sure. The unit you choose must be able to handle both the sensible heat load and the latent heat load on your hottest, most humid day in summer with full occupancy and all your gear running, and likewise must also be able to handle the coldest day in winter with no occupancy and all your gear off.

1 - Create two separate rooms. One for music, the other as the office /garden room:

Acoustically, this sounds like the best plan to me, but you are short on space and short on budget.

Isolation: The wife would like large windows (perhaps bifolds) to open out to the rest of the garden /barbecue area. Having the music room separate from the garden room will reduce costs of double bifold doors and the inherent reflective surface they would introduce.

I'm not following. Maybe you skipped a sentence or two in there? The explanation does not seem to fit the reasoning.

The distance between the CLP and side walls will be too small to use diffusion.

The entire studio is too small to use diffusion, no matter which way you do it. Sorry. That's off the table in such a small room. You need at least 3m between your head and the surface of the closest diffuser, and that's the MINIMUM. If the low cutoff frequency of the diffuser is low enough that three full wavelengths would be longer than 3m, then you'd need to increase that distance accordingly. So your studio cannot have diffusion at all: it's just too small.

Also, I'm not sure why you would want diffusion in the side walls? That's what you seemed to be suggesting with your comment above... or maybe I just misunderstood it?

Room nodes will be more disruptive and need more treatment to stop the room ringing at many different frequencies

That's does not make sense at all: It's going to be a small room no matter which path you take, so it is going to need a large amount of bass trapping anyway: that goes without saying. There is no need at all to try to treat individual modes separately (and indeed, that isn't even physically possible). Your only option for bass trapping is deep porous absorption in a room that size.

I'm also not sure why you think that modes would necessarily be more disruptive in this case?

This option would be a 1:1.42:1.67 music room (2.3m(H) x 3.27m(W) x 3.84m(L)

I think there's a typo in there some place! That would give you only 12m2 floor area! So there's clearly something wrong there. Barely more than half the minimum size, and only about one third of the total floor area. I suspect that you made an error in the dimensions somewhere.

And why is the ceiling so low? 2.3m? Is there a reason for that? I thought you said you were tall, and needed a high ceiling?

Potential room size 2.1m (H) x 4.54(W) x 6.22m(L) = 1:2.16:2.96

That's a lot better in surface area, but why so long and thin? Also, your ceiling height is almost exactly three times the length (within 5%), so that's not a good ratio at all.

And why did the ceiling go down even lower? If You can build the ceiling at 2.3m for the "two-room" plan, how come it cannot also be 2.3m for the single room plan? 2.1 is unusably low for a studio.

Isolation: No separation between music kit and garden room.

And "dining" is no longer an option, of course. So this does not seem to be a good idea. I'm sure your wife would not be happy about investing all that money, then not being able to use it for entertainment!

I’ve entered the above sets of dimensions into amroc and been very scared by the results.

Right. The ceiling is just too low in both cases.

Unless you are able to reduce RT60 down to like 0.2 seconds, these dimensions all look to be really bad!

I don't understand what you are saying at all: Why would you NOT want a decay time of 200 ms, for a small room like that? What reason could you have for wanting a longer decay time in a control room? You might want to go a little higher, but not much. ITU an EBU specs for that room say 209 ms, while AEC suggests 270. Probably something around 230 to 250 would be a good point to aim for, but certainly not over 300ms. I'm confused as to why you think this is a bad idea.

I'm also not getting what you mean by the comment at all: Changing the decay time of the room as a whole has no effect on the modal spread. The modes will remain in exactly the same relationship. Modes are related ONLY to the dimensions of the room, not to the treatment. The modes will still be there, potentially, regardless of the decay time.

It looks like you need a room the size of wembley stadium before room modes are no longer a problem.

I'm not sure if you've ever been to a game at Wembly Stadium, but I somehow doubt that the acoustics there would make for a good control room!

Yes, in theory, you need a room with dimensions a minimum of 18m in all three axes, but with a good ratio between them, to have no modal issues. Very true. But such a room would be unworkably large (not to mention complicated and expensive to build!), so we have to live with modes. That's the problem with small rooms: they don't have enough modes, and the spread is lousy.

Yet I have worked in many small studios 3m x 4m x 5m.. ish, which all sounded fine after a little bit of treatment.

Well, rooms that size will need more than "just a little bit" of treatment, but yes, they can sound fine. Take a look at the graphs for this room, for example:

http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471

Not a single problematic mode in site! Yet the room is somewhat smaller than Wembly Stadium.... Studio design is all about balance, compromise, treatment, and optimization. As long as you design the entire treatment system correctly, you can get fairly decent response even in smallish rooms.

But not in 12m2!

Am i getting overly worried about the room mode calculator?

Yes. Modes are only one of MANY issues in room design.

Which layout do i choose? - 1 or two rooms

I would go with two rooms, definitely, but with a far more reasonable size of control room!

When using room ratios and measurements, should I measure the internal dimensions from face to face or should i go by the internal sides of the heavier outer walls, floors and ceilings?

The internal walls of the room: The hard, solid, massive walls, floor and ceiling surfaces that you see as you stand inside the completed room, before you put any treatment or furniture in it. That's the dimensions you use to calculate the modal response. If your walls are not designed/built correctly, then there might also be some secondary effects from the outer shell, and lower frequencies of course, but that should not bee an issue if you design/build right.

Which type of roof - warm or cold, pitched, monopitched or flat?

I'm not sure what you mean by "warm or cold" roof: Are you talking about vented vs- unvented? If you do a vented roof deck, then you will need a three-leaf ceiling system. If you go with unvented then you can just do two leaves, but unvented is riskier.

Personally, I would go for a normal gable roof, vented, three-leaf, with higher mass on the middle leaf. That allows you to get good ceiling height, and provides plenty of space to fit in your HVAC system as well.

How high should I go? What is the optimum ceiling height for a small control room.

Certainly higher than 2.1m! And higher than 2.3 as well. I would shoot for 2.5, if possible, or even more.

The specs for control rooms do not define the height: They only define the minimum floor area (20m2), the acceptable range of ratios, and the acceptable decay times relative to a theoretical room with a volume of 100m3. You can find all of those in specs such as BS-1116-3 and TECH.3276. As long as you have enough floor area, and a reasonable ratio, you can go as high as your budget allows.

Is there an ideal room ratio for rooms under 100m3, and should I aim for that?

100 m3 is pretty big! You'd need a ceiling of over 3m to get that in a building whose footprint is only 30m2. And no, there are no ideal ratios for that size, or any other size. There are several bad ratios that you should try to avoid at all costs, and there are some reasonable ones that you should try to get close to, but there is no such thing as an ideal ratio for small rooms. It is physically impossible. But that does not mean that you roll over and die if you can't get a good ratio for your room! It just means that you'll have to work harder treating it and tuning it.

Regarding Ceiling height - I want the best sound but don’t want to piss off the neighbours or run the risk of not getting planning permission. Anyone with similar suburban UK experience that can share their experiences would be most welcome.

see above . . .

Once I have some answers to the above, I will start to create a Sketchup document of the layout and then add detail for wall sections, Wall to floor sections, wall to ceiling etc

Ummmm... With SketchUp, you do not "create wall sections" or "floor sections". You just model the parts of your room in 3 dimensions. That's all. You can then view that model in many ways, including sectional views if you want, but also plan views, elevation views, perspective views, parallel projection views, and even animated walk-throughs. SketchUp is a 3D modelling package, not a CAD system.

and then perhaps start to look further into details such as spacing and type of rubber pucks to support the inner walls & floors...

That's easy! I can help you with that! You will need a total of zero pucks, and they will be spaced infinitely apart... Refer to the link I gave you above for full details. In short. with a concrete slab on grade floor, that's it. You are done. Your floor is finished. You don't need anything else. If you don't like the look of concrete, or want a floor that is warmer to the touch (and visually warmer too), then just lay ordinary laminate flooring over a suitable underlay, and you are done.

how do I suspend the ceiling etc.

That's also easy! You don't suspend the ceiling! As simple as that. You just build it on top of the inner-leaf walls, and you are done. The only special care that you need here is to make sure that the inner-leaf ceiling does not touch the outer leaf in any way at all: there can be no mechanical connection between the inner leaf and outer leaf: not even a single nail. The inner-leaf is built as a complete self-supporting stand-alone structure, that just happens to be located within the outer leaf. That's it. Nothing complicated. As long as you keep them separate, then you do not need resilient channel, suspended ceilings, rubber pucks, or anything else that is exotic / expensive / complicated.

Please let me know if I have missed any important information or if there are any books which i should order and get my head around during this design stage.

I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais.



- Stuart -

[AlunH]

Hello Stuart,

Wow, thanks for the welcome and your swift and energetic response.

I suppose you could combine dining and office, but it seems that 3 rooms would be best. But in only 30m2, that's not much space at all! Specs for control rooms call for a minimum of 20m2 if you want decent acoustics

Ok, so that answers many questions, including some further down the page regarding floor areas. First, it will have to be two rooms. The more i think about this, the more sensible it would be to combine music and office and leave the garden room as an area which has wide openings to the outside. Sliding patio doors or bi-folds etc.

Given our budget, I think we will need to make compromises on the acoustics by having a control room below 20m2. A 1:1.4:1.9 room with your recommended ceiling height would result in 2.5m(H) x 3.5m(W) x 4.75m(L) = 16.625m2

…where the few modes that are available are bunched up together at just a couple of notes, THATS when you have problems. Not because of too many modes,..

Aha, I see. So, we are trying to ensure that the room has modes equally spread so that each frequency in the musical scale is being affected as near to equal as possible. That way we don’t hear too many peaks or troughs at certain frequencies or in certain positions? I think the books you recommended will help.

In fact, you'll probably have to do it without any windows at all on that budget.

Hmmm, Not ideal! I do have a supplier of relatively cheap double glazed units. In the control room I was hoping to have at least one narrow window (middle of soffit wall) with one DG unit in the exterior cement block wall with a fabric frame to another DG unit on the inner leaf. Is this a reasonable suggestion and if so, should they be mounted so they are not parallel?

Why do you think it will not be possible to get good isolation and decent ceiling height? I don't understand the problem.

Well, I was working on the assumption that the internal floor would be at least 125mm above the external ground. Then I was assuming a raised floor on top. (although you have since told me that I can have bare concrete and not need to isolate the control from floor) of 125mm. I was expecting the ceiling (which you say can just be mounted on the internal walls) would drop another 150mm (4” thick frame with a 25mm air gap and two sheets of plasterboard) form the internal roof level… Thats 400mm loss in height in total. Subtracted from a maximum eaves height of 2.5m = 2.1m. If I were to build up to the boundary (2.5m MAX building height for Class E) I would lose another 225-250mm. bringing the floor to ceiling height inside to a measly 1.85m… I am 1.96m I am intrigued how you manage a 2.5m floor to ceiling height inside with a max eaves height of 2.5m and the internal floor not being subterranean ? :/

Hence going for planning permission.

…Monitors should NEVER by on the desk, or the console meter bridge, …

I am aware of the comb filtering from adjacent mixing desks or other flat surfaces which create a reflected path, very similar in length to the direct. But what would you suggest to allow me to use the NS10s and the Tannoys?

.. Or you might want to consider adding a sub to get down into the lows..

I also have a Tannoy TS-10 sub which extends down to 29Hz. I always thought that subs were a bit of a no-no in control rooms but I bow to your superior knowledge. Any suggestions on where this should be sited. I would imagine, in the middle of the front wall but will this depend upon the final rom size, materials etc?

.. perhaps have a slate /rock tiled…. front wall

I was considering just using these split face wall tiles at about £40 m2. For a front wall 2.5m x 3.5m (with a 1.75m2 window) that would only be 7m2 = £280. IT LOOKS SO PERRTY!

to change the acoustic response of the room from "neutral" to "live"

Oh well, that’s not a deal breaker. I am also aware that adding lots of synths or other shiny surfaces are going to have an effect. but I am not that concerned. I can always remove them form the room if it becomes an issue when mixing.

.. Mass does not absorb sound…

My poor, simplistic language. From what I understood, increasing the mass of a resonator would change its resonant frequency. Books will be arriving this week!

just do a simple monolithic slab on grade..

I am searching through all 31 pages of “slab on grade” results to get an idea of how to pour this. All i have found by googling is that the slab should be (for colder climates such as ours) poured over a slab of sealed insulation and DPM to ensure good thermal qualities. However, I read another post on this forum where a slab poured on top of insulation was referred to as a “floating floor” which was not optimal. Do you have any threads you could point me at for the correct way to achieve the right result please?

Quote:
THE ROOF: (I haven’t decided on warm or cold roof yet) To keep it simple (i don’t know how to design roof trusses)
Then maybe you should learn, or hire someone who does?

All of a sudden, I feel the need for an architect.

just go with a standard gable roof

Wife likes Gable roof. Well, that’s that decided then.

OCB Flooring

\

I meant OSB. My Bad.

All of the above combined with the soffit mount, leads me to suspect that you are trying to do an RFZ design here. Is that the case? Or did you have something else in mind?

I though that is the preferred method to get the best possible stereo imaging with minimal amount of comb filtering from early reflections. Could you enlighten me further?

Your only option for bass trapping is deep porous absorption in a room that size.

Could you point me to some detail on construction for this kind of thing. I have seen instructions on making corner traps from rock wool slab enclosed within a simple wooden frame with fabric starched over it. I have also seen wide band absorbers made using a frame covered with MLV and loaded half full with rock wool. The MLV and air inside the frame act as a resonant spring whilst the rock wool acts as an absorber. Which of these would you suggest as the best approach or is it a case of lets deiced on the room dimensions and then work out what is best?

Probably something around 230 to 250 would be a good point to aim for

OK, I see the logic for a more ‘dead’ control room. I will aim for 230ms. I have read that 290 is more comfortable and natural and may be better if i am to combine the music room with the office and use the outer, second room for entertainment only. This makes more sense from a layout /usage perspective. As stated, the music room will not be a professional space as such, I just want to make sure that i do all i can to ensure the room dimensions and acoustics benefit rather than impair its use.

….Well, rooms that size will need more than "just a little bit" of treatment, but yes, they can sound fine. Take a look at the graphs for this room, for example:

l viewtopic.php?f=2&t=20471…. But not in 12m2!

Crikey. That’s flat! OK, so how about 16.625m2? Am I likely to get by with that? Because that’s already a pretty big shed!… and i still have to find space next to it for a garden room that can accommodate a sofa, a pinball machine, a pair of turntables, a 1.8m x 1.8m record shelf and 1500 vinyl LPs! - The bar is definitely going to have to be an outdoor affair... I feel a veranda coming!

If your walls are not designed/built correctly, then there might also be some secondary effects from the outer shell, and lower frequencies of course, but that should not bee an issue if you design/build right.

Would 2x4 timber frame with rock wool slab and double 12mm plasterboard be considered “built right”? Should I brad nail these direct to the concrete? What if i want a wooden /laminate floor? lay floor after walls get built?

Personally, I would go for a normal gable roof, vented, three-leaf, with higher mass on the middle leaf.

I like the idea of the gable roof. Do you have any examples of the this method of constructing the roof. I will do further searches but not found any so far.

That's easy! I can help you with that! You will need a total of zero pucks, and they will be spaced infinitely apart... …In short. with a concrete slab on grade floor, that's it. You are done. Your floor is finished. You don't need anything else. If you don't like the look of concrete, or want a floor that is warmer to the touch (and visually warmer too), then just lay ordinary laminate flooring over a suitable underlay, and you are done.

I like this approach. Sounds simpler and cheaper… unless you forget to run service ducts and draw wires first!! What is the best way to fix the walls to the floors? What about thermal insulation below the slab? (as previously asked - above)

'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais.

Arriving this week, I hope!!



Once again Stuart, thank you very much for the warm welcome and of course, your customary sarcasm. I feel i got off lightly compared to some… Hehehe!

I will take some time to digest what you have given me so far and do my best to learn more about the concepts involved. Ultimately I think we will need to go for a Music room /office of around 2.5 x 3.5 x 4.75 with a garden /entertainment space on the side of it, enclosed inside a single storey building, under a large gable roof. Perhaps with a porch. The two rooms will be separated internally by a double wall.

Given the larger footprint and longer walls, I may need to introduce piers in the longer walls or use thicker blocks. I will be consulting an engineer for this. I have also decided it may be worth adding EPS insulation to the inside of the outer wall to help with the overall R value. This will result in a smaller air gap. do you think this will matter?… enough questions perhaps.

Once I get a grip on the dimensions, will you be able to help and advise on the the finer points of acoustic treatments? I really appreciate the free advice but am conscious that this is after all your livelihood!

Any how, I am waffling!

Many Thanks,
Alun

[Soundman2020]

So, we are trying to ensure that the room has modes equally spread so that each frequency in the musical scale is being affected as near to equal as possible. That way we don’t hear too many peaks or troughs at certain frequencies or in certain positions?

That's the concept, yes. In fact, you really want several modes associated with each note on the musical scale, but at low frequencies that is impossible in small rooms. Basically, think of it this way: hypothetically, you have maybe 20 notes to cover, and only five modes to cover them... So clearly you can't even get one mode for each note, let alone many! In fact, most notes will end up with no modes at all. And that's the problem. And there's nothing you can do about it...

I do have a supplier of relatively cheap double glazed units.

Those are no use for studios, unfortunately. They are made of thin glass with thin air gaps, which produces a rather high MSM resonant frequency. And since the MSM resonant frequency defines the isolation to a large extent, you don't get good isolation for low frequencies. Those units are fine in houses and offices for typical ambient sounds, and typical house/office sounds, where most of the energy is in the mid range, but no use for studios, where there is a lot of energy in low frequencies.

with one DG unit in the exterior cement block wall with a fabric frame to another DG unit on the inner leaf. Is this a reasonable suggestion and if so, should they be mounted so they are not parallel?

That would be a four-leaf system. Even worse than a three-leaf system, for low frequency isolation. Two-leaf is the optimal arrangement. So: one thick pane of glass in the outer leaf, and another in the inner leaf.

Angled mounting is another one of those myths... it makes things worse, not better. Since the MSM resonant frequency depends on the size of the air gap (distance between the leaves, or between the panes of glass in this case), angling one of the pieces of glass must, by definition, make the gap smaller on one side. Smaller gap = higher frequency = worse isolation. You get optimal isolation with parallel glass. Yes, that does create ideal conditions for various other types of resonance and standing waves forming between the panes, but the overall effect is still better when the panes are as far apart as possible. The only valid reason for angling glass in studio walls, is to prevent light glare getting back to: you want to be able to see through the glass, not to just see a bright reflection of your light bulbs mirrored back at you, or maybe a reflection of your own face, or the back of the console! Those issues can be minimized by careful design, and careful placement of lights, so there really is not much reason to angle your glass.

I am intrigued how you manage a 2.5m floor to ceiling height inside with a max eaves height of 2.5m

Read carefully: That's the height of the EAVES ... Take a look how they measure that height. Your roof can still go up to 3m with a flat roof, or 4 meters gabled. a 4m gabled roof with raised collar tie trusses gives you plenty of extra room to have a ceiling that is higher than 2.5m

Of course, if you build within 2m of the boundary, all bets are off, as your maximum height can only be 2.5m in that case. Simple solution: don't build within 3m of the boundary! Or see if you can get a waiver to allow you to angle part of the roof such that all of the roof that is within 2m of the boundary is still under 2.5m, but the rest can go higher.

I am aware of the comb filtering from adjacent mixing desks or other flat surfaces which create a reflected path, very similar in length to the direct. But what would you suggest to allow me to use the NS10s and the Tannoys?

Put them on stands behind the desk. Large, heavy, massive stands, of the correct height such that the acoustic axis of your speakers ends up at around 120 cm above the floor, which is standard height.

I always thought that subs were a bit of a no-no in control rooms

Take a look at the acoustic response for the smae room I already linked you to before: www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=20471 That room has not one but TWO subs, even though the mains (Eve SC-407's) already go down pretty low. So yes, you can use subs in a control room! Of course, it's better to have just the mains, in which case, you'd need mains that go down to 20-something Hz, and cost an arm and a leg, plus half a knee-cap and three fingers! Or you could add a sub, carefully placed and carefully tuned, to fill in the low end.

Any suggestions on where this should be sited. I would imagine, in the middle of the front wall but will this depend upon the final rom size, materials etc?

Actually, the middle of the front wall is NOT a good spot for a sub! It sets up interference patterns in the room... the best position is found by testing, once the room is finished, but it's normally close to the front wall, but off to the side a bit (not centered). So in your design, leave space out there for you to move it around.

I was considering just using these split face wall tiles at about £40 m2. For a front wall 2.5m x 3.5m (with a 1.75m2 window) that would only be 7m2 = £280. IT LOOKS SO PERRTY!

The key to successful soffit mounting is that the infinite baffle (front panel of the soffit, the one with the hole in ot for the speaker to poke through) must be massive (very heavy), as well as fairly smooth and flat. The reason it is called an "infinite baffle" is because it is supposed to extend the original front baffle of the speaker "infinitely" in all directions. Of course, it isn't really infinite, but it needs to pretend that it is. It has to be solid, massive, hard, rigid. Stone meets that, for sure, as long as it is real stone (not fiberglass imitation). But building a stone-faced soffit is complicated, and expensive, and I don't think you have the luxury on your budget. Yes, the stone itself is not expensive, but the base you need behind it to hold it up adds complexity and expense, and hiring a stone mason to do the work is also not cheap. Plus, then you have the not-so-minor issue of what to do if the speaker fails, and needs repairs, replacing, or adjusting...

the slab should be (for colder climates such as ours) poured over a slab of sealed insulation and DPM to ensure good thermal qualities. However, I read another post on this forum where a slab poured on top of insulation was referred to as a “floating floor” which was not optimal.

That's two different things! The actual building slab itself is poured on top of insulation in cold climates, yes, and that's not a problem. In fact, it's good! A "floating floor" is one that is built on top of that slab, as a secondary floor, much like what you had in mind originally. The reason yours would not work is because it does not have enough mass: in order for a floating floor to work, it must have considerable mass, such that when you walk on it, or put "things" on it (such as instruments, equipment, furniture, stacks of pizza, crates of beer...) that does not altar the total mass significantly. An 80 kg person standing on a wooden floor deck that only weights 160 kg itself, changes the mass by 50%! The same person standing on a concrete floor deck that weighs 1000 kg, only changes the mass by 8%. No problem. So the correct way to float a floor is indeed, with a concrete slab that is "floated" above the actual building slab, by some type of resilient system.

But you don't need that! You need only the base slab for the building itself. For your purposes, that's plenty. And that one does in deed need to be on top of insulation, for thermal reasons, not for acoustic reasons.

Good "monolithic slab on grade", and see what you come up with....

All of a sudden, I feel the need for an architect.

The architect comes later (if at all). What you need now is a studio designer. He designs the building to be a studio, then hands that design over to the architect, who checks it for local code compliance and draws up the actual paper plans that your local authorities will need. It's a mistake to let an architect design a studio! Something like letting a vet do brain surgery on people....

I though that is the preferred method to get the best possible stereo imaging with minimal amount of comb filtering from early reflections. Could you enlighten me further?

Right. RFZ is, indeed, the best way of doing it. But RFZ is not just soffits. That's a part of it, yes, but there's more to it than that. There's a whole process, and a set of specifications that you need to aim for, if you want an RFZ style control room.

I have seen instructions on making corner traps from rock wool slab enclosed within a simple wooden frame with fabric starched over it.

That's commonly called a "corner trap", ans is the most basic type. It can be effective if the insulation is of the correct type, and thick enough.

I have also seen wide band absorbers made using a frame covered with MLV and loaded half full with rock wool. The MLV and air inside the frame act as a resonant spring whilst the rock wool acts as an absorber.

That's commonly called a "membrane trap". It's a variation of the "panel trap". You sort of have the idea right, but a bit off: The MLV acts as a "limp mass membrane" in that configuration, and it is actually the moving "mass" of a "mass-spring-mass" system. The other "mass" in that system, is the rigid panel at the back of the trap. Together they create a sealed (air-tight) cavity. Along with the MLV membrane at the front, that is a tuned system. It resonates at one specific frequency, given by the equation f=60 / SQRT(M * D), where M is the surface density of the MLV and "D" is the depth of the cavity. Also, the insulation inside the cavity does not act as an absorber: more correctly, it acts as a damper. It damps the resonance, in addition to improving the efficiency of energy dissipation, as well as broadening the tuning slightly. In other words, it lowers the Q. The problem with membrane traps is that they are tuned! They are not broadband. They only react to their tuned frequency. But you will need to deal with several different problem frequencies, not just one or two, so using tuned devices is not the best option: you'd need to cover all of the walls and the ceiling with many such devices, each tuned to one specific frequency, then located in the room at the point where that problem actually can be treated!

Plus, membrane traps take a while to "start up" and do their job (resonate along with the problematic frequency, in order to absorb it), and then take another while to "die down" after the frequency is already gone. So after the note stopped, the trap carries on ringing for a few cycles... Thus instead f shortening decay times, membrane traps can actually lengthen them! Or in the best case, not shorten them enough.

Which of these would you suggest as the best approach or is it a case of lets deiced on the room dimensions and then work out what is best?

There are two "best traps", and I use them both. One is called "Superchunk", an the other is called "hangers". You make the superchunk by cutting panels of semi-rigid insulation into large triangles (about 60cm to 90cm along the two sides adjacent to the right angle), then stacking up those triangles, floor to ceiling, in the room corners. They are very effective down to quite low frequencies. Hangers are built by making a "sandwich" with two panels of insulation glued to a homosate core, made long enough to hang pretty much the full height of the room (ceiling to floor), leaving just enough space above and below so that the don't actually touch. Maybe an inch or so gap. You hang several of those next to each other, with gaps between them, all across the entire back wall.

OK, I see the logic for a more ‘dead’ control room. I will aim for 230ms. I have read that 290 is more comfortable and natural and may be better if i am to combine the music room with the office and use the outer,

It's not about making the room "dead" or "live", or "comfortable" or "pleasant", or "warm" or any other thing like that. It's about giving it the optimum psycho-acoustic response for the volume of the room, such that it sounds "natural" and "neutral" to our brains. If you take a look at ITU BS.1116-3, you'll see that the actual decay time is referenced to a hypothetical room with a volume of 100 m3, using an equation. And it's not just the overall decay time that you are trying to achieve, but rather that the decay time is the same in all frequency bands, across the spectrum. So the 2kHz band must decay at the same rate as the 32 Hz band, and also the 20 kHz band. That's not so easy to achieve especially in small rooms, but that's what you should be aiming for: to get as close as you can to the ideal.

Crikey. That’s flat! OK, so how about 16.625m2? Am I likely to get by with that?

Well, you won't get the same response as Studio Three, which took years of design, building and tuning to get to that point (not to mention lots of money!). That room is 48m2 area and 180 m3 volume, so you won't be able to match that with 16m2. But you can certainly get something reasonably decent with 16 m2. Here's some graphs from a room I did for a customer in Canada. The area is 13.8m2, and the volume is about 30m3:

Low end frequency response:

mkca-cr--final--fr-low-end-after.jpg

Low end spectrogram:

mkca-cr--final--sp-low-end-after.jpg

RT-60.

mkca-RT-60.8k.jpg

Not too shabby for a tiny room!

Would 2x4 timber frame with rock wool slab and double 12mm plasterboard be considered “built right”?

Assuming your outer-walls are concrete block, and that you leave a small gap between that and the inner-leaf stud wall you describe, that would give you fairly good isolation, approaching 50 dB. But I would go with 16mm drywall, instead of 12mm.

I like this approach. Sounds simpler and cheaper… unless you forget to run service ducts and draw wires first!!

Well, that's probably a good reason why you should not forget to do such things!

A well-respected acoustician and designer, who sometimes posts here on the forum, has a motto: "Building a studio is 90% design, 10% construction". He's right. The more time you put into design, the faster, better, cheaper, and more effective the actual construction will be. Taking care with the design helps avoids expensive mistakes. Forgetting to run utility lines and plumbing in the slab is an expensive mistake!

What is the best way to fix the walls to the floors?

Building code normal requires anchor bolts. You can either use "J" bolts that you set into the concrete right after you pour it, before it hardens too much, or you drill holes later and put expansion bolts in.

thank you very much for the warm welcome and of course, your customary sarcasm. I feel i got off lightly compared to some… Hehehe!

What? You mean I didn't give you a fair dose? Damn! I'll have to fix that in later replies! Can't have members not getting their fair share of sarcasm! Sheeesh! I must be slipping...

Seriously, there's actual a good reason for the "in your face, no holds barred, no punches pulled" style: It gets your attention! It gets you to notice what I'm saying. It points you at things you might not have seen, or might have glossed over if I wrote in a wishy-washy, waffling, easy-going, Disney rainbows and butterflies style....

it may be worth adding EPS insulation to the inside of the outer wall to help with the overall R value.

Actually, you need to fill that entire cavity with suitable fiberglass or mineral wool insulation. Not just part of it, but the whole thing. That has pretty good R value!

This will result in a smaller air gap. do you think this will matter?… enough questions perhaps.

Compare the total R value of that layer or EPS by itself, vs. filling the entire cavity with insulation.

will you be able to help and advise on the the finer points of acoustic treatments? I really appreciate the free advice but am conscious that this is after all your livelihood!

That depends on how much advice you need, and how long you are prepared to wait to get it. My paying customers obviously get first priority (which is why I'm sometimes away from the forum for days, or only posting a couple of brief responses), and there's often dozens of active thread on the forum, so the free advice can occasionally take days or weeks to appear! You got lucky today, as I happened to see your reply while I was looking for something else and also had a few minutes free, but it likely won't always work out like that. So it might take many days to get a response from me on the open forum. As long as you are OK with that, when it should work out fine!


- Stuart -