John Sayers' Recording Studio Design Forum Archive

Hi, 1st post here, and I still have plenty of reading to do. But here is my thought process so far!
I'm at the researching/planning phase for a new multi purpose building we'd like to put in our back garden. We have a 12ft x 24ft outdoor pool and we'd like to build a "Summer house" near it, so that we can "go on holiday there" for the day and keep an eye on the kids. I'd like to get some basic drawings done so that we can apply for planning permission, and get some builder's quotes. So the exterior dimensions are the 1st priority to fix.

My wishlist of requirements is

Pool House/summer house:-
- Sliding windows onto the pool area and garden. bi-folds would be nice but I expect we'll need 2 x sliding doors for the sound insulation.
- Bathroom/wetroom with toilet and shower. Changing room next to it.
- Open plan main area
- Small kitchen/sink/worktop area with space for 2 or 3 appliances under the worktop
- Space for fridge
- Easy to clean hard wearing flooring, will get wet.

Home Office/Photography/Painting studio
- All year round usage - heating
- Open plan area
- Natural light through sliding doors
- Method of making main area pitch black.
- Storage for equipment - easy access to loft

Guest Room
- 2 sleeping areas. Bunk beds in changing room. Sofa Bed in main area.
- Method of making the rooms dark
- All year round usage - heating and ventilation

Home Cinema
- Dimensioned for good acoustics
- Acoustic treatments to be aesthetically pleasing
- Motorised projector screen
- Wall mounted L+C+R speakers (possibly floor L+R, but want to keep the floor space as open as possible)
- Wall or floor mounted other speakers
- Subwoofer.
- Ceiling locations for Atmos
- Method for making main area pitch black.
- All year round usage - heating, cooling, and ventilation
- Sound insulation
- Equipment can be in the loft
- Loft ideally partially insulated as well so temp change not too high for stored equipment

Band/instrument practice room/recording room
- Dimensions for good acoustics
- Acoustic treatments to be aesthetically pleasing
- Sound insulated ideally to allow the use of acoustic drums
- Ventilation, heating, cooling for all year round usage
- Possibly use the changing room as control room in the future if recording

Here are some pictures of what I have in mind.


We are located fairly rurally, and we have neighbours both sides whose houses are in line with ours. I measured the outdoor noise one evening using a RadioShack meter as 50dBc rising to 60 as traffic goes past on the main road about 30m away. The ambient noise would drop further I expect.

It would be nice to use acoustic drums in the room, but I am not sure if that is going to be practical. At last rehearsal, our volume was around 100dBc.

Questions:-

- I'm budgeting around £1000 per square metre, so £40k. How realistic is this? I can do some of the interior work myself, so I intend to get quotes for up to watertight.

- What should I allow as the eaves/gutter height? I am not sure of the internal ceiling construction yet - more reading to do.

- What would be a suitable wall construction detail? From my reading, then my 1st pass is
- Render
- 100mm dense Block
- 100mm cavity with 75mm thermal insulation board fixed to inner leaf
- 100mm dense Block,

Then, internally, either

- 75mm?? airgap with 50mm acoustic insulation fitted in airgap
- 50mm x 75mm CLS framing attached to floor and ceiling.
- Soundblock plasterboard 15mm
- GreenGlue
- Soundblock plasterboard 18mm

or

- 100mm?? airgap with acoustic insulation fitted in airgap
- 50mm x 75mm CLS framing attached to inner block leaf.
- 50mm acoustic Insulation in between the framing?
- Resilient channel attached to framing
- Sound block plasterboard 15mm

- GreenGlue
- Sound block plasterboard 18mm

- I expect to use a Minisplit for heating and cooling, but need to allow for ventilation. Would this best be a fan intake drawn from a roof vent on the pitched room? Also need ventilation in the bathroom.

- Will I need double sliding doors in the window openings, and a double door arrangement for the entrance door? I have allowed 500mm for the total thickness of each wall.

- Would this achieve my goal of acoustic instrument practice? Is any of this overkill?

- Is the length width depth ratio of the living area suitable for good acoustics? I assume ceiling height will be 2.2 to 2.4m. I have read that there are multiples that should be avoided.

- Floor will probably be a concrete slab onto clay soil with some thermal insulation board sandwiched. More reading to do. Are there any acoustic considerations here?

- What else do I need to think about at this stage? (ie. to fix exterior dimensions for planning permission and get basic construction quote from builders.

- Any view on what the planners are likely to say?!

Hi there "a366666643", and welcome!

My first impression when reading over your post is that you are trying to do to much in too little space. Some of your uses have directly conflicting acoustic requirements. For example, a home theater ("HT") needs to be rather dead, acoustically, but a rehearsal room needs to be rather live acoustically. So there's a major conflict right there. It is possible to build variable acoustic devices that can be flipped, opened, closed, rotated, slid, angled, folded, or otherwise changed in some fashion, order to modify the acoustic response of the room, but that adds to the complexity and expense, and takes up extra space, and might conflict with yet another of your requirements: good aesthetics.

For example, here's a variable acoustic device under construction that I designed a few years back for one of my customers:
You can see the two hinged sections that can either be folded out across the central slot wedge unit, or folded the other way, up against the absorber panels to the sides, thus changing the room acoustics and decay times. But that's a pretty big unit, and you need space in front of it to be able to swing the modifier modules out and back. And you'd need several such units in your room, to have enough effect on room acoustics that you could use the room for both HT and also rehearsal.

So it's possible to do what you want, but with limitations.

However, there's one area where I would definitely not compromise: water. You do NOT want wet people in wet bathing suits coming into and out of your HT / rehearsal room. Bad idea. By all means have sliding doors into the change room / bunk bedroom and bathroom, but you should absolutely prohibit entry to people who are damp. For one thing, you'd be overloading your HAVC system, as it vainly tries to deal with the gross humidity spike, for another you'd have all your acoustic treatment soaking up that moisture in the air, and likely developing fungus over time, or at least that ugly dank musty smell that emanates from thick fibrous materials that have not managed to dry out properly. And thirdly, many musical instruments change their tone as the ambient humidity and temperature around them changes. (Ever had to re-tune an acoustic guitar multiple times, every few minutes, after you bring it out of the cold dry closet, into the warm moist living room?).

Water and studios do not mix. So there would be no door at all form the wet room to the main room, and entry of wet people would be prohibited by law, under penalties involving boiling oil, being buried up to the neck in an ant hill, or forced to attend parliament sessions every day for a month. OR something equally unpleasant.

But let's take a step back, and get down to basics: isolation. That's the most fundamental parameter that needs to be defined before you can think of anything else. It defines the method of construction for the entire building, which in turn sets limits on many other aspects of what you can and cannot do.

So, you mentioned that you have ambient levels of around 50 dBC, which is rather high, but you also need to check your local regulations, by-laws, community rules, as well as your national codes on how loud you can be legally. You can probably find that on your local municipality web site, or with a visit to their offices. That's what you should be aiming for: not exceeding the legal limit for sound leaving your property. Let's assume it is around the typical ridiculous levels imposed by most authorities: 40 dB at night. I say at night, as I'm assuming that the home theater and rehearsal space activities will be mostly evening / night / weekends. So 40 dB is what you are aiming for. You cannot send out more than 40 dB at your property line. You don't say how far away your proposed building is from the property line, but let's assume just a couple of meters, to be safe. 40 dB is terrible. It basically makes it illegal to even whisper loudly as you walk down the street: try it with your meter! So that's the stupid limit that you'll have to aim for, if you want to keep your place legal.

On the other end, your HT will be calibrated for 85 dBC, which implies it can hit over 100 dBC for intense scenes, where huge canon are firing at each other, or earthquakes are decimating the world, or people are screaming in terror as they get slowly mangled by unspeakable monsters to an suitably accompanying screeching thumping nerve-wracking soundtrack, or galaxies are colliding, or other such common Hollywood effects. So your 100 dBC inside has to be strangled down to no more than 40 dBA outside. That implies around 60 dB of isolation, or a bit less actually, since we are talking "A" vs. "C" weighting here.

That's for the HT. But for the rehearsal room, it's a different story.... read on!...

At last rehearsal, our volume was around 100dBc.

Either you have the world's quietest drummer, or your meter is broken! Typically, a drum kit can put out fifty to a hundred times more energy than that. Drums are commonly measured at 115 dBC when played reasonably hard, and maybe 120 dBC when Gorilla George the Drummer goes wild after one too many... Add to that a ripping, roaring bass guitar on an amp that goes up to 11, plus electric guitars, keyboards, percussion, amplified vocals.... It's not hard for a typical garage band to put out 115 dBC, without trying too hard. But let's say for argument's sake that you manage to keep your group under control (using threats of converting the pool into a tar pit and duping anyone in there that plays too loud), and you achieve a rather quiet 110 dBC at your sessions, inside the room.

So, on the one hand you have 110 dBC inside, and on the other you need to be 40 dBA on the outside, 2m away. That implies that you need around 60 to 70 dB of isolation (taking into account the difference between A and C, yes). Let's say 60, to make it easy on you.

60 dB of isolation is a very, very tall order.

A typical house wall (plasterboard on both sides of a stud frame, with insulation inside) will get you around 30 dB of isolation. The dB scale is logarithmic, not linear, so each time you go up ten dB, you are producing ten TIMES more energy, and need ten TIMES more isolation. So a wall that gets you 60 dB of isolation must block one thousand TIMES more energy than a wall that gets you 30 dB. It's that simple. And that complicated.

So, you need to stop about a thousand times more energy than a normal house wall does for 60 dB, or ten thousand time as much if you need to shoot for 70 dB. Which is why I said it was a tall order.

Most home studio designers aim for isolation of around 50 dB, and are really pleased if they hit it, after taking extreme measures to get there. If they manage to get 55 dB, then they are whoopingly, screamingly happy. And getting 60 dB would put them over the moon, in a coma of extreme ecstasy.

So that's what you are up against.

Even getting 50-something is a big achievement, and can only be attained by going to extremes.

- I'm budgeting around £1000 per square metre, so £40k. How realistic is this?

My customers in the UK tell me that it costs them somewhere in the region of £1000 to £1500 per m2 to build a studio from the ground up, so you are in the ballpark, but only just. You are very much on the low end of the range.

- What should I allow as the eaves/gutter height? I am not sure of the internal ceiling construction yet - more reading to do

In the UK you have several legal options for building your place, and each one has it's own limitations. If you go with "permitted development", class 1A or 3A, or more likely Class E, then you'd be limited to a maximum roof peak of 4m if you are more than 2m away from the property line and the roof is gabled, 2.5m if you are closer then 2m, or 3m otherwise. That's the roof peak. The eaves cannot be higher than 2.5m. That's for permitted development, but if you go with planning permission you can probably get a waiver. Take a look at pages 40 through 47 of the latest version of the "Permitted Development Rights for Householders - Technical Guidelines". The latest was updated April 2017.

- 100mm dense Block
- 100mm cavity with 75mm thermal insulation board fixed to inner leaf
- 100mm dense Block,

Then, internally, either

- 75mm?? airgap with 50mm acoustic insulation fitted in airgap
- 50mm x 75mm CLS framing attached to floor and ceiling.
- Soundblock plasterboard 15mm
- GreenGlue
- Soundblock plasterboard 18mm

That's a three-leaf wall. Since you want high isolation down to low frequencies, I'd suggest only a two-leaf wall, never one leaf, never three leaf, never four, etc. Only two. I would suggest a sand-filled concrete block (CMU) wall as your outer-leaf, rendered (thick) on the outside, sealed on the inside. Then your inner-leaf would be a totally separate, independent stud frame with a base layer of 19mm OSB on the studs, then at least two layers of 19mm drywall (plasterboard), or perhaps one layer of fiber-cement board and one layer of drywall, with full-schedule coverage of Green Glue on each layer. The depth of the air cavity between the outer and inner leaves will be determined by the final isolation level that you set as your target, and the lowest frequency that you need to isolate.

But that's only the walls: Your ceiling, windows and doors will also need to be very heavy, in order to keep the same high level of isolation that you need. So sliding glass patio doors are entirely out of the question here. If you did want sliding glass doors, they would have to be custom built for you, using very thick laminated glass, and multiple seals that are activated by the door handle: they retract and extend into place when the handle is operated, prior to the door moving. That's an expensive door, and you need two of them back-to-back (one in each leaf), but it's the only way to get the high isolation that you need and still have sliding glass doors.

And of course, the same applies to your HVAC system.

- I expect to use a Minisplit for heating and cooling, but need to allow for ventilation. Would this best be a fan intake drawn from a roof vent on the pitched room? Also need ventilation in the bathroom.

Mini-split is fine for the heating / cooling / humidity control, but your ventilation system will be a lot more complicated than a simple vent and fan!

In order to isolate a room, it MUST be air-tight. Absolutely hermetically sealed. The reason is simple: if there is some place that air can get in or out, then so can sound, because sound is nothing but vibrations in the air. So to get high isolation, you need high air sealing: not even a single tiny crack under the door, along the edge of a wall, or through the electrical system. Nothing. Each leaf of your building must be fully sealed, air-tight. However, you do need to breathe! You do need to replace the entire air volume inside your room around 6 times per hour. So that implies smashing a huge gaping hole through your fantastic air-tight walls, so you can have one large duct to bring in fresh air, and another large duct to take out the stale air! You see the problem. The need to breathe is in direct conflict with the need for hermetic seals. The solution is to put in something called a "silencer box" at each point where a duct goes through a wall leaf. The silencer box works similar to the way the muffler works on your car exhaust system: it allows gas (air) to move through, while preventing the sound from getting through. It consists of a series of solid baffles arranged inside a massively thick, rigid box, and the interior is covered with a special (expensive) acoustic material, called "duct liner". It is specifically designed and tuned acoustically such that it blocks the maximum amount of sound while allowing the correct amount of air to flow through at the correct speed, while also not increasing the static pressure so much that the fan can't handle it. Designing silencer boxes (also called "baffle boxes") for studios that need high isolation, is not a simple task. You will need four of those: two on the supply duct, and two on the exhaust duct.

- Will I need double sliding doors in the window openings, and a double door arrangement for the entrance door?

Yes, and as I mentioned above, those doors will need to be massively heavy, with multiple seals, because you need such high levels of isolation.

I have allowed 500mm for the total thickness of each wall.

That might of might not be enough. You will only know when you do the calculations.

- Would this achieve my goal of acoustic instrument practice? Is any of this overkill?

A) Probably not. B) No, it's "under-kill".

- Is the length width depth ratio of the living area suitable for good acoustics? I assume ceiling height will be 2.2 to 2.4m. I have read that there are multiples that should be avoided.

Yes, mathematical multiples in dimensions should be avoided, as should dimensions that fall within 5% of being a mathematical multiple of another dimension. There are also other rules and guidelines, but those are mostly meant for studio control rooms, not so much for rehearsal rooms or HT. Use one of these Room Ratio calculators to figure out the best dimensions for your room:

http://www.bobgolds.com/Mode/RoomModes.htm

http://amroc.andymel.eu/

Both of those are very good, and will help you to decide how best to build your room. They give you tons of information that is really useful to help figure out the best dimensions. But you don't need to go crazy here: Just pick a ratio that is far from the bad ones, and reasonably close to one of the good ones. Anything in the Bolt area would be good for you, or even something just outside the Bolt area might be OK.

- Floor will probably be a concrete slab onto clay soil with some thermal insulation board sandwiched. More reading to do.

If you have clay soil, you'll need to hire a structural engineer with experience in soil mechanics, to help you design the foundations. My guess is he'll want you to go fairly deep, and lay a gravel bed then the insulation, then the vapor barrier, then a monolithic slab, and he'll likely want rebar in the trenches and steel mesh in the slab. That's what I would do for poor clay soil.

Are there any acoustic considerations here?

Make it thick, and keep it decoupled from any other concrete around it, such as the pool, or the house. It must not be connected in any way to any other building or slab.

- Any view on what the planners are likely to say?!

Unfortunately, I dropped my crystal ball last week, so I can't help you much there!

Seriously, it's really hard to say. You might get a guy who is open and easy going and want's to help guide you through the red tape. Or you might get a real nasty so-and-so who's having a terribly bad day and is determined to block your every move! Hopefully you get the former, not the latter. Surprisingly, most inspectors are not out to get you, and really do want your place to succeed, so they'll probably offer good advice on how you can make your plans meet code, and what you can do to improve things, save money, etc. As long as you go in with a well thought out plan, in reasonable detail, and good documentation, and you have already made sure that it meets your local building code requirements, and follows typical best practices, you should be fine. If you go in with a beer-stained wrinkled bar napkin that has a terrible sketch in lipstick, then your chances are pretty low! But if you go in with nicely done drawings showing good dimensions and details of construction materials, and intelligent questions, you stand a much, much better chance.


- Stuart -

Hi Stuart, thank you for the very detailed reply - much appreciated. I am digesting it. Essentially I'll need to reduce my expectations!

A couple of questions initially.

1. Are there hinged glass doors rather than sliding doors that would be better suited?
2. How does the CMU + stud wall compare thermally with the standard cavity wall?

I'll come back after more reading!

Thanks,
Al

1. Are there hinged glass doors rather than sliding doors that would be better suited?

Yes, there are. You can buy them, or you could even site-build them yourself, to save money, if you have decent carpentry skills.

Here's a series of photos from a set of doors that were site-built by one of my customers in Australia. The glass is not as big as you are wanting, I think, but the same principles can be applied to a wood framed door having a much larger area of glass:
The above is just a normal door blank, solid wood, after the hole is cut out for the glass.


In this one, two other layers of wood have been added, in order to beef up the mass and also to provide the surfaces for the multiple seals.


Here, the basic frames are in place in the rough opening, read for the doors, jambs and seals to be added

That's with just the inner door hung and aligned, and the jambs in place, but without the seals.

Both doors are in, with all the jambs and seals in place

How it looks from the outside. Note the heavy duty automatic door closers on both doors


A view from the outside with both doors open. You can see the multiple heavy-duty hinges: those doors are HEAVY!


With that setup for the doors (along with all the other stuff we did!) he manages to get a little over 55 dB of isolation, and he's VERY please with it. He teaches drums, so he sometimes has two drum kits going together. His neighbor is maybe 5 m away, and they hear practically nothing at all during the day, and only very faint, slight sound at night if they are standing outside, but indoors with the windows closed, it's dead silent. He is able to jam at all hours, with no problems with the neighbors. There's still some sound getting up into his own house, but that's only because he hasn't yet completed the full isolation system. Once that is done, he should be getting close to 60 dB all around, with a bit of luck. Even the way it is now, his wife and kids are happy.

So yes, it is possible to site-build doors with glass, and that can save you a ton of money. Commercially available acoustic glass doors will cost you an arm and a leg, but you can build them yourself for considerably less.

2. How does the CMU + stud wall compare thermally with the standard cavity wall?

There should be no problem there. As I mentioned above, the idea is not to use just plain CMU's, but rather to fill the internal cavities with sand. That serves to add mass, and damping, and also therefore adds a lot of thermal mass. You will then have your inner-leaf, which will also have a lot of thermal mass, and between them will be a large air cavity that is totally filled with insulation. Several inches of it. Since there is no mechanical contact at all between the two leaves, there is also no thermal bridging: no path at all for heat to move between the two. But the biggest point is that both leaves will be sealed hermetically. That's a major factor. Houses get cold mostly due to air leaks. Most people don't realize just how leaky their houses are! Air can get in and out through numerous small cracks, gaps, holes, etc. including the electrical system, etc. Close off all of those, and you'd save a stack on your heating bill! But a studio is, by definition, sealed absolutely air-tight, TWICE over, not just once. Each leaf is completely sealed. And so is the electrical system. So there's no way to lose heat through the biggest single path where houses lose it: air leakage. In fact, it's probably that you won't need much heating at all: you are more likely to need your HVAC running in cooling mode, when you have a few musicians in there with their gear and instruments, jamming away happily. Body heat and equipment heat will build up inside, and has nowhere to go, except through the ventilation system. And if you put an ERV or HRV on that, you can even recover a large percentage of that heat too.

- Stuart -

I am back... Thanks to the thread and forum I realise what it takes to get this kind of attenuation, and I've decided that this is primarily a living area, so we should prioritise that. Otherwise we'll spend extra to try and build something that doesn't look nice and also doesn't attentuate the noise...

l'll have to cancel most of the attenuation requirements - we could still do band rehearsals, but we'd have to use electronics and IEMs.
We will want to put bi-folds in, and possibly a skylight, so straight away they are the weakest points.
Our architect is suggesting a warm mono roof covered in EPDM rather than the pitched roof on the diagram.
I will still have a projector screen and associated sound system in there so I will make sure the room dimensions are dissimilar, and attenuate the sound from that as practically as possible.

My main question is therefore:-

Does it still make sense to consider the proposed 2 leaf sand filled concrete block construction considering that a bi-fold will, I believe typically attenuate only 30dB?

Cheers!

Does it still make sense to consider the proposed 2 leaf sand filled concrete block construction considering that a bi-fold will, I believe typically attenuate only 30dB?

Right. It does not make sense to go to extreme measures for isolation if there will be a major weakness in the design such as what is basically a large hole in one wall.

considering that a bi-fold will, I believe typically attenuate only 30dB?

I very much doubt that you'd get 30 dB of isolation from a typical single bi-fold door! Maybe 20 something. To get more than 30 dB of isolation from a bi-fold, you'd need to take many precautions, such as using only solid (not hollow) doors, very thick, very heavy, with high quality seals all around all edges. You can buy proper acoustic rated bi-fold doors that will get you more than 30 dB, but those are expensive.

Originally you were going with sliding glass doors: What made you switch to bi-folds?

You really should start by defining how much isolation you need, in decibels! With that number in hand, it's dead easy to figure out what type of construction you need, and how to go about it. Take into account that isolation is only as good as the weakest part. If you have a bi-fold door that only gets 25 dB of isolation, then it does not matter how good the rest of the isolation is, your total isolation is 25 dB. But if it turns out that you really need 45 dB, and you only get 25, then you will have wasted a lot of time, money and effort for nothing.




- Stuart -

I'm back, and I'm hoping that with your help there is still a way of splitting the use.

You really should start by defining how much isolation you need, in decibels! With that number in hand, it's dead easy to figure out what type of construction you need, and how to go about it.

Let me try and answer this question 1st. I want to be able to play music/films without annoying the neighbours. If ambient is 50dB and the HT peaks at 100dB, then that suggests 50 to 60dB isolation. From previous comments that is a tall order, but hopefully can get close without too much compromise. The "annoyance factor" will vary quite a bit depending on time of day and time of year. I am assuming for reference that our existing house with 15 year old double glazing will have isolation of 25dB.

Here is what we have just had a lawful development certificate through for.
The idea here is that we could add an internal wall and door where the yellow line is. The area to the right hand side could be the HT. The area to the left could be the "entertaining" area. There is now a separate outside entrance to the bathroom, so wet people do not traipse through the HT. Points that occur to me. The bifolds might get changed to sliding doors, but the plan is that any sound is already attenuated before it reaches any windows or external doors.

• It would be nice to have a high level rectangular window in The HT area but not essential if that would compromise the isolation too much. To make the space multipurpose, for example musical instrument practice I would want to put lighting in that could provide a comfortable non-claustrophobic area. Not sure if some LED wall panels would work to give the impression of natural light through frosted windows? I could change the "liveness" and colour of the HT room by using movable dark heavy curtains around the walls.
• I believe then that the roof will be the weakest point acoustically. The building will have a flat roof. Permitted development allows a max of 2.5m to the top of the roof. However, because the ground is sloping I have 3 to 3.2m external height to play with. I believe a standard warm roof construction from bottom to top of plasterboard, 125mm joist, OSB, vapour barrier, PIR insulation, EPDM will give 40 to 50dB isolation. I have enough height I think to add layers of plasterboard or OSB, or resilient channel to get the isolation up a bit more.
• The external wall will be clad with something, possibly larch or a man-made non-combustible equivalent. Because the building will be used intermittently, I think IWI will be better than EWI, so that it heats up and cools quickly.
• Extract and make up air vents could be boxed in at high level, go through the corridor outside the bathroom and use the head room in that corridor to house the baffles etc. I do not have a feel yet for how big or long these need to be - more research needed.
• I'm assuming the internal walls will 150mm to 250mm thick, using some or all of multiple layers of plasterboard, greenglue, resilient channel, acoustic rockwool, and/or double studs, depending on the isolation I want.

So I'm back to the question of whether this is going along the right lines, and if so, then what should the external wall construction look like. Still worth doing hollow blocks filled with sand, then a gap, then stud frame etc. as per 1st reply? How do I work out whether interstitial condensation will be a problem between the leaves?

My objective is to narrow down the external construction of the building so I can get a spec put together and get some quotes for the ground works and shell.

Thanks for reading this far!

Let me try and answer this question 1st. I want to be able to play music/films without annoying the neighbours. If ambient is 50dB and the HT peaks at 100dB, then that suggests 50 to 60dB isolation.

Right. That's reasonable.

From previous comments that is a tall order, but hopefully can get close without too much compromise.

50 is achievable reasonably easily, if you work with care. 60 is harder, but still "do-able". 70 is about the limit you could hope for in a home studio, and is really hard to achieve, unless you have very deep pockets!

I am assuming for reference that our existing house with 15 year old double glazing will have isolation of 25dB.

Probably a little more than that, but that's a reasonable assumption. It's always best to underestimate how good your current isolation is, and overestimate how much you need.

the plan is that any sound is already attenuated before it reaches any windows or external doors.

You can do it that way if you want, but it is also feasible to have exterior windows and doors in a studio.

It would be nice to have a high level rectangular window in The HT area but not essential if that would compromise the isolation too much.

Not a problem. Glass has roughly three times the density of drywall, so it's pretty good for isolation, as long as you make it thick enough.

To make the space multipurpose, for example musical instrument practice I would want to put lighting in that could provide a comfortable non-claustrophobic area. Not sure if some LED wall panels would work to give the impression of natural light through frosted windows?

That would work. No problem. As long as you located your frosted panels at positions in the room where they wont cause unwanted acoustic reflections.

I could change the "liveness" and colour of the HT room by using movable dark heavy curtains around the walls.

To a minor extent yes. Curtains can help to damp a bit of the high end, yes, but they do little for the mids, and nothing at all for the lows. A room that small will need bass trapping.

I believe a standard warm roof construction from bottom to top of plasterboard, 125mm joist, OSB, vapour barrier, PIR insulation, EPDM will give 40 to 50dB isolation.

I doubt it! Maybe 35 or so. Perhaps 40 if the EPDM is very thick. But you are describing roof and ceiling together there: if you wnat good isolation, you would need to NOT put any plasterboard on the bottom of the joists, and rather build a separate ceiling that rests only on your inner-leaf walls.

I have enough height I think to add layers of plasterboard or OSB, or resilient channel to get the isolation up a bit more.

RC can gain you a little, yes, but you won't be getting 60 dB isolation with RC.

Extract and make up air vents could be boxed in at high level, go through the corridor outside the bathroom and use the head room in that corridor to house the baffles etc. I do not have a feel yet for how big or long these need to be - more research needed.

The more isolation you need, the more complex HVAC is. You'll have to do the math to figure this part out. You need a flow velocity no higher than 300 fpm at the registers, and a flow rate that is high enough to give you at least 6 room changes per hour. Based on that, you can determine what size ducts you need, and how big the silencer boxes need to be. Your isolation will dictate the construction of the silencer boxes: Use whatever material you need to get roughly the same surface density as that of the leaf itself. Usually that means a layer or two of MDF, OSB, plywood or something similar, and the interior needs to be lined with a 1" thickness of proper duct liner, designed specifically for the interior of HVAC ducts.

I'm assuming the internal walls will 150mm to 250mm thick, using some or all of multiple layers of plasterboard, greenglue, resilient channel, acoustic rockwool, and/or double studs, depending on the isolation I want

Assuming that your inner-leaf walls are properly designed, fully decoupled from the outer-leaf, then you do not also need RC (Resilient Channel). The purpose of RC is to decouple, but if the framing is already decoupled then there's no point in decoupling it again! And a fully decoupled frame is much better than RC on a non-decoupled frame.

then what should the external wall construction look like. Still worth doing hollow blocks filled with sand, then a gap, then stud frame etc.

That is certainly a possibility, and would indeed get you good isolation. In that case, the limiting factors would be the doors, windows, HVAC system and the ceiling.

How do I work out whether interstitial condensation will be a problem between the leaves?

As long as the leaves are built correctly, and sealed correctly, then there should be no problem.

- Stuart -

Stuart, thank you for the rapid reply - your words give me the encouragement that this is not a hopeless effort!

I'll use this thread to record my thoughts and questions, not all will be acoustic related and can be answered by the architect or builder. The questions marked in red I would appreciate your guidance on if possible, and anything else I need to think about at this stage.

My next step is for the architect to draw up the technical drawings. I want to be ahead of him. I expect to break the build quote down into 3 main stages "up to slab level", "watertight" with the the final fitout following on afterwards. If the HT is a room inside a room, then I can defer much of the decision making for now.


Foundation & Floor
Expecting foundation trenches & standard single level concrete slab across entire footprint.
Decisions/questions needed at this stage that will materially affect the cost

• Final size and location of slab
• Insulation level for building regs
• Will insulation go below concrete or above it
• How wetroom will be sealed and drained and does this affect the slab
• If the entertaining area will get wet people on it regularly, then does that affect what we do with the slab, or is that a finished floor question only
• Finished floor level relative to pool and surrounding area
• Where will we break into the 110mm sewer. Will it need rerouting
• No floating floor for the HT, same slab height and finished floor level as the rest of the building.
  
• Any other acoustic considerations at this stage?

"Deferred Questions"

• Incoming service location (electric, water, network)
• Internal drainage pipe routing

External Walls
Decisions/questions needed at this stage that will materially affect the cost, because they affect the slab size.

• How should I finally decide whether to use sand filled CMU versus standard construction for cladded buildings which I think would be cladding, batten, single skin lightweight or medium weight solid blocks, batten, then PIR backed plasterboard with in built vapour barrier for the entertaining area. The HT will be different as a room within a room. I need to strike a balance between performance, total wall thickness and cost. There is no point over-engineering the external wall if the roof will be the limiting factor. What is the rough acoustic and thermal performance difference between sand filled CMU versus standard?
• If sand filled CMU, how is this sealed on the inner face to stop condensation?
• Should I use sand filled CMU for the full perimeter of the building, or just along the 2 external walls around the HT area.
• How do I calculate the air gap needed between the inner leaf and the outer leaf for the HT room within a room?

Roof
Decisions/questions needed at this stage that will materially affect the cost.

• What will be the finished height of the building. Constraint is the HT room within a room, so I need to calculate the airgap between the HT ceiling and the joist.

Cheers

Wonder if anyone can point me in the right direction with my red questions above please?

Rereading the replies, I had thought only the HT would be a room within a room, with the rest of the internal rooms being of normal construction as they do not need to be isolated. Is there any reason this would not work?
Thanks!

a366666643 wrote:Wonder if anyone can point me in the right direction with my red questions above please?

Rereading the replies, I had thought only the HT would be a room within a room, with the rest of the internal rooms being of normal construction as they do not need to be isolated. Is there any reason this would not work?
Thanks!

Hi, thought I'd way in whilst Stuart is occupied.

a366666643 wrote:How should I finally decide whether to use sand filled CMU versus standard construction for cladded buildings which I think would be cladding, batten, single skin lightweight or medium weight solid blocks, batten, then PIR backed plasterboard with in built vapour barrier for the entertaining area. The HT will be different as a room within a room. I need to strike a balance between performance, total wall thickness and cost. There is no point over-engineering the external wall if the roof will be the limiting factor. What is the rough acoustic and thermal performance difference between sand filled CMU versus standard?
If sand filled CMU, how is this sealed on the inner face to stop condensation?
Should I use sand filled CMU for the full perimeter of the building, or just along the 2 external walls around the HT area.
How do I calculate the air gap needed between the inner leaf and the outer leaf for the HT room within a room?
Roof
Decisions/questions needed at this stage that will materially affect the cost.

When considering your external leaf, the standard light/medium weight concrete blocks will likely be fine ie. high enough mass (which type are you liking at?), it would be best to face these by rendering the exterior, as by cladding them you add another (unsealed) leaf to your wall, which can reduce your isolation (although if your concrete blocks are dense enough it's probably not a problem).

Your HT can be the only "room within room" in the building, but you will have almost no isolation between your HT and the rest of the building, and that's both ways. Also the other rooms become part of your 2 leaf wall. So they must be fully sealed too. If you open any doors or windows you now have next to no isolation from/to the outside world.

To have an idea of the performance of your walls and roof calculate the resonant frequency of them using this formula.

Fx = 43 * [(m1 + m2) / (m1 * m2 * d)] ^0.5

m1 and m2 are the mass of each wall leaf (kg/m2). d is depth of the cavity (m). This will give you the resonant frequency of the wall providing the cavity is fully filled with insulation. Do the same for the ceiling. Increase the cavity depth and/or increase mass on the leaves to lower the resonant frequency.

You want to resonant frequency to be around half the lowest frequency you need to isolate if you can. Eg. a bass guitar low E is 42Hz. So you want around 21Hz resonant frequency to isolate this frequency well.

Remember, your ceiling is like your walls. You need an exterior leaf (completely sealed) an air gap, and an interior leaf (completely sealed). These leaves can't be connected in any way. Best way is to sit a new set of joists on top of your "room within a room" and fix your inner ceiling to those.

Just a note: If part of the building is not decoupled 2 leaf, as you have described, you must make sure when finishing the other sections the builders dont attach anything to your "room within a room" that couples it to the exterior leaf. They can't just plasterboard the internal walls including your HT room wall. One method would be to build a second stud wall infront of your HT wall without touching it and when lining any door openings seal the cavity with rubber membrane and cover with fabric to finish it/extend the lining close enough to your HT wall door lining to caulk the gap to finish it.

If you havent looked already, look at here for images of this sort of thing:

http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm

If you need to reduce sound between the HT and the entertaining room you need two doors on these walls, as described in the link above.

Hi, thought I'd way in whilst Stuart is occupied.

Thank you Waka

To have an idea of the performance of your walls and roof calculate the resonant frequency of them using this formula.

Fx = 43 * [(m1 + m2) / (m1 * m2 * d)] ^0.5

m1 and m2 are the mass of each wall leaf (kg/m2). d is depth of the cavity (m). This will give you the resonant frequency of the wall providing the cavity is fully filled with insulation. Do the same for the ceiling. Increase the cavity depth and/or increase mass on the leaves to lower the resonant frequency.

You want to resonant frequency to be around half the lowest frequency you need to isolate if you can. Eg. a bass guitar low E is 42Hz. So you want around 21Hz resonant frequency to isolate this frequency well.

Thank you for this, so with a double stud wall with a cavity of 200mm, and 2 layers of soundbloc plasterboard both sides, that gives me an Fx of 27Hz. with 300mm cavity 22Hz.

I've changed the layout to get double doors between the HT and the other room without having to have a door in the main wall between the rooms. Walls are not yet to scale, I'll do that next. I've read about not making the walls parallel but I don't think I'll get away with that here! Will it have much impact?

I worry about the HT being small dark and dingy with no windows, and dark walls. My wife is already calling it the dungeon! I do want it to be multi-use, and most of the pics I see are of larger spaces. My space looks like it will be 3m x 5m. Does anyone have any pics of a similar sized space?

a366666643 wrote:

Hi, thought I'd way in whilst Stuart is occupied.

Thank you Waka

To have an idea of the performance of your walls and roof calculate the resonant frequency of them using this formula.

Fx = 43 * [(m1 + m2) / (m1 * m2 * d)] ^0.5

m1 and m2 are the mass of each wall leaf (kg/m2). d is depth of the cavity (m). This will give you the resonant frequency of the wall providing the cavity is fully filled with insulation. Do the same for the ceiling. Increase the cavity depth and/or increase mass on the leaves to lower the resonant frequency.

You want to resonant frequency to be around half the lowest frequency you need to isolate if you can. Eg. a bass guitar low E is 42Hz. So you want around 21Hz resonant frequency to isolate this frequency well.

Thank you for this, so with a double stud wall with a cavity of 200mm, and 2 layers of soundbloc plasterboard both sides, that gives me an Fx of 27Hz. with 300mm cavity 22Hz.

I've changed the layout to get double doors between the HT and the other room without having to have a door in the main wall between the rooms. Walls are not yet to scale, I'll do that next. I've read about not making the walls parallel but I don't think I'll get away with that here! Will it have much impact?

I worry about the HT being small dark and dingy with no windows, and dark walls. My wife is already calling it the dungeon! I do want it to be multi-use, and most of the pics I see are of larger spaces. My space looks like it will be 3m x 5m. Does anyone have any pics of a similar sized space?

Capture-building2.PNG

The layout looks ok, but just having two doors doesn't isolate the rooms, you don't seem to have a room within a room for your home theatre (unless that's just the drawing) you would need your second set of walls inside the home theatre section.

Something like this: You wouldn't need to use any of the other rooms as an airlock as you have a door on each leaf of the HT. If you want to use the little hall way section as an air lock you could get away with a single door on the inner leaf of your HT, but the you would need both the door to the entertaining area and out side to be heavy doors with (expensive) air tight seals, which would be more expensive anyway.

With regards to angled walls, you could do that but it's only for flutter echo and would require both walls to be 6 degrees angled or one 12 degree. It is probably easier to treat the walls with alternating absorption instead.

With regards to the darkness of the room, this is for the home theatre effect I assume? Acoustics don't care about the colour of your walls. You can have as much glass as you can afford in your HT if you want, but it costs a lot to make them sealed properly with very thick glass. Probably 1 pane of 15mm thickness on the inner leaf and 1 pane of 18mm of the outer leaf. Plus having it framed and sealed airtight. That link I showed you before for the doors has windows on too.

Just try not to put windows at the first reflection points of your speakers; probably safe to put them on your front wall and front section of your side walls, but you will have to design the speaker locations before you will know.

Hi all, thanks for the guidance. Here is what the architect has come up with. Starting to get some costs now. Can anyone see any problems?

One question I have - To build a 200mm cavity on an internal double stud wall using 38x89mm studs, then there will only be 22mm between the studs, which won't have any insulation in it. Is this correct?

Plan Elevation Spec

Foundations:
Plain concrete strip foundations - min 750 -1000mm deep, 600mm wide x 150mm thick (min). Size and depth to be agreed on site with building control. Allow for increased width to footing along the south west elevation (adjacent to garage wall); raised ground level to be adequately retained using dense concrete blocks laid flat to form retaining wall.

Floors:
(0.22 W/m²k) 65mm sand & cement screed on 100mm concrete slab with A142 reinforcement mesh (40mm min cover) on 300mu vapour barrier on 70mm Celotex FR5000 insulation on 1200 gauge DPM on 50mm sand blinding on 150mm well compacted hardcore. 25mm Celotex TB4000 insulation to perimeter of slab. DPM to link with DPC in walls - subject to building inspector’s requirements.

Walls:
New External Walls: (0.28 W/m²k) Entertainment room: Horizontal larch timber boarding on vertical 50 x 25mm SW treated battens on dpm strips on 100mm Durox Superblock 4 outer leaf. 100mm cavity (50mm clear) 50mm Kingspan Kooltherm K112 board to outer face of independent inner leaf stud wall: Proctor Frame Shield 150 breather membrane on 12mm WBP plywood sheathing on 38 x 89mm CLS studs @ 400 cts with noggins @ 900mm vertical cts with vapour control layer and 2 layers of 15mm soundbloc plasterboard - skimmed finish internally. Studwork to be filled with 100mm Knauf Earthwool acoustic roll.

Pool/Summer house:
Horizontal larch timber boarding on vertical 50 x 25mm SW treated battens on dpm strips on 100mm Durox Superblock 4 outer leaf. 50mm clear cavity. Inner leaf: Proctor Frame Shield 150 breather membrane on 12mm WBP plywood sheathing on 38 x 89mm CLS studs @ 400 cts with noggins @ 900mm vertical cts, 75mm Kingspan Kooltherm K112 framing board between studs with vapour control layer and single layer of 12.5mm plasterboard - skimmed finish internally. Wall ties: Stainless steel, maximum 900 mm cts horizontally, 450mm cts vertically, across cavity between leaves and at jambs. Cavity Trays: Non pitch polymer cavity trays and DPC’s to manufacturer’s recommendations. Proprietary cavity closer at openings. Blockwork movement joints at 6m max spacing and bed joint reinforcement above and below openings to manufacturer’s recommendations. Lintel requirements to be confirmed by engineer.

New Internal Walls:
Acoustic separating wall between entertainment room and pool room: Double independent stud walls each to consist of: 2 layers of 15mm soundbloc plasterboard on 38 x 89mm CLS studs @ 400 cts with noggins @ 900mm vertical cts. Studwork to be filled with 50mm Knauf Earthwool acoustic roll and skimmed finish.

WC/Shower room and lobby Enclosure and load bearing wall:
47 x 95mm studs @ 400 cts with noggins @ 900mm vertical cts, 12.5mm plasterboard lining to lobby and pool room side, 12.5mm moisture resistant plasterboard lining to WC walls and Knauf Aquapanel cement board lining to shower enclosure walls.

Ceilings:
Entertainment room: Independent structure supported from independent timber frame inner walls: 47 x 175mm (C16) ceiling joists filled with 100mm Knauf Earthwool acoustic roll, with vapour control layer and 2 layers of 15mm soundbloc plasterboard to underside and skimmed finish.

Pool/Summer house:
MF (metal frame) suspended plasterboard ceiling, hung from flat roof joists; vapour control layer and single layer of 12.5mm plasterboard with skimmed finish.

Roof:
(0.18 W/m²k) min 1:60 fall Sika Sarnafil or EPDM single ply membrane adhered to 120mm Celotex Crown-Fix insulation on 18mm OSB 3 deck on 47 x 175mm (C16) SW joists @ 400mm cts. - Refer to section above for type of ceiling finish.

Rainwater drainage:
uPVC – where required, new gullies and below ground drainage to connect to existing as agreed on site with the building inspector.

Windows/ Doors:
All timber or composite timber/ aluminium clad double glazed units with low-E coating, 4:16:4. (U-value 0.16W/m²k). Doors (U-value 0.18W/m²k). All glass, where any part of pane is below 800mm; fixed and opening; all glazed doors to be Class C safety glass to BS 6206. All glazing to meet U values as specified in Part L.

One question I have - To build a 200mm cavity on an internal double stud wall using 38x89mm studs, then there will only be 22mm between the studs, which won't have any insulation in it. Is this correct?

You can see how important filling your ENTIRE cavity with insulation is: That means no insulation voids.

Plan

I can't remember your exact needs, but the larger room design seems off to me. It appears to have an inner leaf everywhere except the windows. Also, the ceiling it's decoupled so why are you adding an inner leaf there at all?

Also, why aren't you maintaining your spring gap size between the two rooms the same as you are to the exterior wall? That smaller gap will increase your resonant frequency. In your Sept 12th diagram, it looks like you have things correct. This new one isn't the same as you had initially planned.

Greg