shed conversion advice please!

[bingo]

Hi All!

I hope you don't mind this post as it's not strictly a studio - but many of the issues and solutions would be directly relevant and of interest to forum members I think.

I'm converting a shed to a dual purpose lounge/living/kitchen area (i.e. home theater one end, kitchen the other) that will be well sound proofed and walls damped to provide good base trapping. Room size about 9m x 6m x 3m. I have an acoustic screen 2.8m wide, seating about 3.3m from screen (which is an issue with room modes I know). 2x18" subwoofers, 11.2 surround speaker system. Structure currently has no ceiling.

My goal is sound proofing and bass trapping via mastic glue (timberflex flooring glue - poor man's GG as per Gedlee) between plasterboard. Listening levels are likely to be 85db - I'm not sure? I have neighbours 6m away. Budget is around $15k, but sound proof doors, paint (and kitchen) are not included (to be later additions).

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My approach thus far (following Gedlee's premium home theater design):

Walls (minimum thermal insulation rating of R2.8 (for comfort)):
1 - 90mm R2 earthwool batt (for thermal insulation) in between existing steel studs.
2 - attached to those steel studs, two layers of 13mm plasterboard, with timberflex mastic in between, on flexible furring channels.
3 - 70-90mm timber stud frame standing isolated (20mm gap) from the adjacent plasterboard wall (sitting on emblefoam, shearflex pads etc.), filled with another 90mm R2 batt (primarily for thermal insulation, and additionally reduce resonance).
4 - attached to the inside of this frame is an identical layer of 2 x plasterboards/1xtimberflex on furring channel.
5 - conventional glass patio door on exterior wall (to be covered with externally with additional solid bi-fold doors)
6 - solid bi-fold (or hollow core with added mass) doors (and damped?) on interior wall (door frame isolated from inner wall with foam).

Ceiling (minimum rating R4.1):
7 - (pitch of roof is actually quite low (15degrees?) so might have to drop ceiling to 2.8m to accommodate insulation, but would prefer not to):
8 - 2x plasterboard/timberflex under roof (or should that go on top of a ceiling framing?)?
9 - ceiling framing - 6m spans of 140x45mm (or 170mm?) timber lengths (plus stringers) at 900 centres for a ceiling frame, resting on isolation blocks, resting on inner frame walls?
10 - under the frame 2xplasterboard/GG, isolation mounts/furring channel?
11 - 175mm R.3.5 batt resting above ceiling, inside timber framing

Crazy? Bad triple leaf effect in walls?

Suggestions please!

[Soundman2020]

Hi there "bingo", and Welcome! I can't believe I missed your first post for an entire month! Wow! Sorry about that!

Better late than never, I suppose...

I hope you don't mind this post as it's not strictly a studio -

Not a problem! Same principles apply...

Room size about 9m x 6m x 3m

For a studio, that would be a REALLY bad set of dimensions, as they are all multiples of each other. Room modes (low frequency natural room resonances) would all occur at the same frequencies like that, causing major "booming" in the low end of the spectrum. If you can adjust those dimensions to a better ratio, that would be advisable. (Even though it is not a studio, I'm assuming you'll play music in there at some point...

My goal is sound proofing and bass trapping

How much isolation ("soundprooofing") do you need?

via mastic glue (timberflex flooring glue - poor man's GG as per Gedlee)

Yeah, I've heard that before, but it isn't. Sorry, but floor glue just is not visco-elastic, and does not act as constrained layer damping. Folks can swear as much as they like that it works "Just like GG", but it does not. It just doesn't. Tehre is no way that it could! It would have to defy the laws of physics in order to do that. Anyone who makes the claim that it does what GG does needs to show the results of their extensive testing in an independent acoustic lab, proving that it does actually work as a constrained layer damping compound. People seem to think that any glue Green Glue if you lay it on thick enough, but they don't realize that Green Glue is not even glue at all! It is not an adhesive, does not stick things together, never was intended to be used as glue, and never even hardens. "Glue" is just part of the name, but it isn't glue at all. So anything that actually is "glue" cannot possibly act like GG does...

In any case, gluing your layers of drywall together would be a big mistake. Unless you used proper Green Glue, which does NOT glue them together...

Budget is around $15k, but sound proof doors, paint (and kitchen) are not included (to be later additions).

I assume that HVAC is also not included!? You won't be able to fit a suitable HVAC system into that budget.

2 - attached to those steel studs, two layers of 13mm plasterboard, with timberflex mastic in between, on flexible furring channels.

As above, skip the glue: It would be a bad choice: Why do you want flexible channels there?

wall (sitting on emblefoam, shearflex pads etc.),

Why? There is no advantage to doing that. Except to the guy who sells you that stuff! You don't need that. Myth.

4 - attached to the inside of this frame is an identical layer of 2 x plasterboards/1xtimberflex on furring channel.

What reason do you have for adding furring channel to an already-decoupled stud frame? You can't get any wetter than wet by taking a hose pipe with you to the bottom of the pool, and you can't get any more decoupled than "decoupled" by adding more decoupling...

5 - conventional glass patio door on exterior wall (to be covered with externally with additional solid bi-fold doors)

Bad idea. You are talking about building massive walls for high levels of isolation, then using tissue-paper for the doors (well, OK, I exaggerate, but you get my meaning.). If you want high level of isolation, then you will need doors that are up to the task.

6 - solid bi-fold (or hollow core

Yup. That's the "tissue paper"...

8 - 2x plasterboard/timberflex under roof (or should that go on top of a ceiling framing?)

Hpow would you attach that? How would you seal it air-tight?

a ceiling frame, resting on isolation blocks, resting on inner frame walls?

Why do you want to isolate your ceiling from the isolated walls? Hose pipe... bottom of swimming pool... If you are fully wet, you are fully wet. If you are fully decoupled, then you are fully decoupled.

10 - under the frame 2xplasterboard/GG, isolation mounts/furring channel?

So you want to take TWO industrial fire-hoses down to the bottom of the pool with you, along with a bucket of water, just to make REALLY sure that you are TOTALLY wet...

If you are fully decoupled, then you are fully decoupled. No point in doing it twice... or threee times...

11 - 175mm R.3.5 batt resting above ceiling, inside timber framing

When you say "R3.5, what is the density and type of insulation? R-rating has no meaning at all for acoustics. What mattes is gas flow resistivity, which is indirectly related to the density of the insulation, and the type.

Crazy? Bad triple leaf effect in walls?

Crazy? Yep. On many counts. Triple-leaf? Yep. In many places.


- Stuart -

[bingo]

Hi Stuart!

I'd almost lost hope and not checked back on this site - but I'm very glad I did! Thanks for your detailed response. Well, it turns out I can't even convert this shed due to council bi laws, so I have to remove it and start with new slab/footings/structure. So, I'm currently planning to go back to my original idea; stawbales! And given your valued critique, it would appear to be a much better plan? According to this link, they should perform very well as isolation, and presumably, the flexible earth render on the walls should act as excellent bass traps.

See here: http://www.thelaststraw.org/strawbale-s ... acoustics/

So what would be ideal room dimensions? I want a minimum of 3m high interior walls, so according to the below link, using the scaleable ratios, 1: 2.16: 2.96, that would give me 3m x 6.48m x 8.88m size room

http://www.acoustics.salford.ac.uk/acou ... ntent=best

For the ceiling, I am now thinking of installing trusses, and then a setup like this:

http://www.ultrafonic.com.au/images/upl ... 202010.pdf

For the patio doors, I'm thinking of trying to sandwich them in between two other solid doors (as a more convention studio double door system) like this (plenty of room in thick 500mm wall in straw bales):

http://www.ultrafonic.com.au/images/upl ... 202011.pdf

And for your interest, I got the ideas about the green glue substitute, and mounting the board on furring channels (to allow thge walls to vibrate to dissipate energy) from Gedlee, pages 199ff:

http://gedlee.azurewebsites.net/downloa ... heater.pdf

Cheers!
Bingo

[Soundman2020]

I'd almost lost hope and not checked back on this site - but I'm very glad I did!

Check your profile settings: You should get an e-mail automatically every time there is an new post on your thread. Also, each time you add a reply yourself, make sure the "Notify me when a reply is posted" box below the text area is checked. If you are not getting notification messages, check your spam filters.

so I have to remove it and start with new slab/footings/structure.

That's actually good news! It gives you the option to do it all correctly, from the start. Mostly my customers want me to design modifications to their existing buildings to fit in their studios, but sometimes they do want me to design "ground-up" studios, and that's a LOT easier to do! It eliminates all of the restrictions imposed by the existing building, and gives you the freedom to build it the best way possible. So if you have that opportunity, you are a lucky fellow!

So, I'm currently planning to go back to my original idea; stawbales!

You know, we've had quite a few forum members come here with the same concept for their studios, but as far as I am aware, nobody ever actually went down that path: It looks good on paper... until you start getting into the details, then it doesn't look so good any more... Also, from the acoustic point of view, you'd be pretty much on your own: I'm not aware of any significant research that has been done on the acoustic properties of straw-bales. There's a lot of anecdotal commentary, yes, and even a couple of isolated studies, such as the one you linked to, but no actual in-depth research. (By that I mean someone who actually takes the time to mathematically model how straw-bales work, and provide equations that could be used to estimate the isolation spectrum for any given straw-bale construction.) You would be your own test lab...

presumably, the flexible earth render on the walls should act as excellent bass traps.

Hmmmm.. interesting word, that... "presumably"... What happens if the presumption turns out to be incorrect? And why do you want your isolation walls to be bass traps? There's a contradiction there, to a certain extent. Bass traps are treatment, which is different from isolation.

I want a minimum of 3m high interior walls,

Any particular reason for choosing that ceiling height?

For the ceiling, I am now thinking of installing trusses, and then a setup like this:

I would not do it like that. The inner-leaf is coupled to the outer leaf. Not a good way to isolate...

For the patio doors, I'm thinking of trying to sandwich them in between two other solid doors (as a more convention studio double door system) like this

That would work, yes, but you only need two doors (back-to-back), and from your comment it sounds like you are talking about three doors?

And for your interest, I got the ideas about the green glue substitute, and mounting the board on furring channels (to allow thge walls to vibrate to dissipate energy) from Gedlee, pages 199ff:

Ahh, yes.... "that" "book". The least I say about it, the better. I would suggest that you buy two real books about this subject: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics, used as an introductory text book in may acoustic courses), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais (a well-regarded acoustic designer, with a proven track record to back it up). After reading those tow, both of which are written in an easy-to-understand style that follows a logical progression from simple concepts through to actual design and construction, you'll understand why my opinion of "that book" is not very high....

Some of the stuff described in that book would very probably not pass inspection, or meet standard building codes, and when you have a book about home theaters that starts out by describing Fourier transformations and ends by saying sub-woofers are not important or worth discussing... well, I'll leave it at that... 'nuff said...

Anyway, getting back to the point: "No-More_Nails" glue is not CLD. Mastic is not CLD. The manufacturers make no such claims, nor do they claim to have tested their products for acoustic properties. The book provides zero support for the claims: no technical data at all, no analysis by respected acoustic labs: nothing but here-say. Compare that to the Green Glue website which provides a huge volume of technical data, including detailed technical reports from independent acoustic test laboratories that show exactly what the product does. ... I know which one I would use!

- Stuart -

[bingo]

So starting the structure anew - is the link to the Salford university research on room dimensions well regarded? That is, would my proposed room sizes be good? 3m x 6.48m x 8.88m.

I want 3m height due to having, don't laugh, Audyssey DSX height speakers that need to be raised up as high as possible. Plus it would give a great sense of living and acoustic space and, if I'm not mistaken, a bigger room would sound better?

Well, if nothing else comes close to green glue, then, due to the size of the room, its price is cost prohibitive for me, as budget is very tight. I acknowledge that research into straw bales is scant, but one study is better than none. Having a desire for good thermal insulation, sound isolation, bass trapping, no moisture trapping problems, and to do my bit to reduce global warming, so straw bales look attractive to me, and for the price (excluding high labour content), evidence suggests they might perform very well. I thought that the flexibility of the render would dissipate sound energy by movement and isolate sound by being isolated from the exterior render. That is, the conventional mass-air-mass isolation approach would be achieved by render-straw-render. The render would have the mass of plasterboard, around 50mm thick each - that's about 4 sheets worth of plasterboard - a lot of mass, but instead of being mounted on double stud walls, it sits directly on the straw bales, which are providing the "isolation". Anyway, I'm sure you understand the idea, but as you say, even if the abstract theory is correct, it needs an acoustic engineer to calculate equations, model, test and what not. So yes, I will be my own guinea pig. Hey, I know it's not gamma radiation, but it worked out okay for Bruce Banner didn't it?

Having said all that, the alternative would be room-within-a-room, double thickness 13mm plasterboard on the inside of the inner studs, and 1x6mm fiber-cement boards on the outside of the exterior. Light fiberglass pink batts 190mm thick in between. No green glue (too expensive). No idea about the ceiling. If you had to put money on it, do you think that setup would perform better than straw bales? Plus I'd have to build bass traps (more cost).

About the ceiling, if I were to use straw bales, I would build a conventional light timber frame stud wall (90x35mm) through which bales would be pushed and then rendered both sides. This would provide no inner wall (as there would be in a conventional room-within-a-room approach) and so, nowhere to sit very long ceiling joists (as it requires a span of 6.5m). So the link was to a solution where an inner ceiling is suspended off the 1st ceiling, with rubber isolation mounts. Note, I'm building this DIY and not a professional builder. So far the easiest way I have found to do this is through simple stud frames and getting pre-manufactured trusses.

Patio doors (i.e. glass) are required by council bylaws - and I would like some natural light in when not playing music loud, so the idea was to put in heavy doors each side that could be closed when sound volumes increase. Similar approach to any other smaller windows if they are needed by code. The other door would be a conventional double door.

BTW, I acknowledge Gedlee did not provide test results, however, in his defense, he does not claim that the suggested approach is as good as green glue, in fact, in forums he has said it is not. However, he does argue that the combined furring channel and no more nails works very well, for a fraction of the cost of GG (without data to back it up as you note). Anyway, I'll investigate those books you recommend.