How to build an "inside-out" ceiling.

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Soundman2020
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How to build an "inside-out" ceiling.

Postby Soundman2020 » Tue, 2019-Nov-05, 13:32

How to Build an Inside-out Ceiling for Your Studio

You might have heard the term "inside-out ceiling", and be wondering what it is, how to do it, and if it has any benefits for your room: This post is all about "everything you ever wanted to know about inside-out ceilings, but were afraid to ask"!


Inside-out Ceiling Concept
First, what is an inside-out ceiling, and what does it do?

Recording studios need "isolation": You need some method to stop unwanted sound from getting out, or getting in. This is commonly achieved by building the studio as a "room within a room", where the original walls and roof of the building are considered to be the "outer" room, then the actual studio room itself is built inside that outer "shell". The inner room also consists of a set of walls and a ceiling, and they do not touch any part of the outer room. This is often called "fully-decoupled two-leaf MSM construction, for reasons that will be discussed in a different post.

Normally when you put up the inner-leaf ceiling in a studio built like this, you install the joists across the room (resting only on the inner-leaf walls), then attach the sheathing under that, by nailing or screwing it into the joists. Here "sheathing" means the layers of building materials that make up the mass for achieving the isolation you need, and that often consists of two layers of drywall (a.k.a. "plasterboard", "sheetrock", "gypsum board", etc), or it could also be one layer of a plywood, OSB or MDF with a second layer of drywall as the final finish surface. For very high isolation, more layers might be needed.

That method is often referred to as "conventional" ceiling construction: this is the way studio inner-leaf ceilings are often built.

But there's a better way of doing the ceiling!

The problem is, if your original "outer room" already has a low roof, or low joists, or low trusses, and then you build your inner-leaf ceiling below that with joists across the room and drywall nailed to the bottom face of the joists, then the final inner ceiling would be very low. But low ceilings are bad, acoustically! One of the key principles of studio construction is to get the ceiling as high as possible, and to have as much air volume inside the room as possible, but with this "conventional" construction method, the ceiling is below the inner-room joists, which are often many inches (cm) deep. That means that the sheathing ends up very low. It would be nice if there was some way of putting the sheathing on top of the joist, instead of under them, as that would gain back the entire depth of the joists, which would make the ceiling a lot higher, acoustically. That would be great if it were possible, but there's no space up there to put the drywall in top, and nail it in place: You couldn't even get a hammer into such a small space! So it seems impossible.

However, there is a method for doing that! Sometimes this is called an "inside-out ceiling". It is called "inside out" because the sheathing (drywall) goes on top of the joists, instead of below them, which is the opposite from a conventional ceiling.

This post describes the method that I have developed for building a studio ceiling "inside-out".

Basically, it works like this: Since there's no space up there to be able to nail the drywall on top of the joists, you don't do that! Instead, you build many small "ceiling modules" down on the floor of the room, each consisting of its own framing with the sheathing (drywall) nailed on top of that frame, then you lift up the modules in between the joists, and attach them to the joists with bolts, screws, nails, etc.

Simple!

However, that would not be very efficient if you just did it like that, with normal 16" (400mm) joist spacing: you would have to build many, many small modules, each just 13" (33cm) wide. It would also make the ceiling very heavy (since each module has it's own frame, in addition to the joists), so you'd need even larger joists to carry the extra load.

So I have developed this method, below.

You start out by building a "backbone" of joists that are spaced much further apart than the standard 16" (400mm), but you double-up, or "sister" two joists at each location, side by side. This means that each of the modules can be much bigger than it would have been, which makes for more efficient use of materials, and less weight in the framing.

CAUTION! You will need to get a structural engineer to tell you how big the joists need to be! Do not just guess, or try to figure it on your own! The joists MUST be large enough to safely support the weight of your ceiling! Don't try to skimp here, thinking you can save a few dollars by not hiring a structural engineer. Your ceiling will weight many thousands of pounds (kilograms), and it if fails, all of that will come down on your head. So make certain that it is designed and built safely. Never do anything structural in your studio without the OK of a qualified locally certified structural engineer.


Typical Inside-out Ceiling Design:

OK, so here's how it is done in practice, with a series of photos taken from an actual home-studio build done by one of my clients, in Australia.

First, the design details in SketchUp, so you can see more clearly how it all works. These views show ONLY the inner-leaf, or inner-room: the outer room that surrounds this one is not visible in these first few images, for clarity.

This is the "backbone" or "skeleton" of the ceiling, consisting of the doubled-up joists and rim joists, before the ceiling modules go in. You can see that the joists running across the room are "sistered": each joist is actually a pair of joists, side-by-side. The large holes in between the joists is where the modules will go:
Soundman--Modular-inside-out-ceiling--101+-Backbone-skeleton-joist-grid--recording-studio-design.jpg


The image below shows just the framing and insulation for two of the modules, temporarily raised into place to check the dimensions and make sure there is a snug fit, before taking them down again to put the sheathing on:
Soundman--Modular-inside-out-ceiling--102+-One-module-frame--recording-studio-design.jpg


Here's how the same two modules would look with the sheathing in place, but with the "backbone" made invisible, so you can see the details.
Soundman--Modular-inside-out-ceiling--103+-One-complete-module-no-backbone--recording-studio-design.jpg


This is a close-up view of the same image, where you can see how the module is built: there's the wood framing, then a layer of plywood, then two layers of drywall on top of that. In this specific case I designed it like that, because the client needed very high isolation for his studio. For a typical studio, the second layer of drywall would probably not be needed. (However, don't guess! Do the math to figure out how many layers you need, and the thickness of each layer, to get the isolation that YOUR studio needs):
Soundman--Modular-inside-out-ceiling--104+-Module-layer-detail--recording-studio-design.jpg


And finally, a view of how it would look with all of the modules in place, and the backbone of joists. The large holes in the two modules at that far end of this ceiling are where the HVAC silencer box sleeves will go through. The silencer boxes are not visible here, but they are located above the ceiling, hanging down from the outer-leaf framing above. Those holes are where the thick wood "sleeves" will pass trough the ceiling.
Soundman--Modular-inside-out-ceiling--105+-All-modules-and-backbone.jpg



Typical Inside-out Ceiling Construction

The above is the design for this specific room: your room might need another design: all rooms are different, but the same principles apply. Now for the actual construction photos:

View from inside the room, looking up towards the completed joist backbone. You can see the outer-leaf ceiling just above the joists. In fact, it looks like the inner-leaf joists are touching the outer-leaf joists, but in reality they are not touching: there's a gap of about 1" (2.5cm( between them. This is VERY important! For maximum isolation, the inner-leaf cannot touch the outer-leaf anywhere! Not even a single nail. They must be completely independent from each other, with no mechanical connection at all.
Soundman--Modular-inside-out-ceiling--201--Backbone-in-place--recording-studio-construction.jpg


One module being raised into place, between the backbone joists. The client used a car jack to raise the modules (they are heavy), with a metal pole and bracing system that he invented. It worked very well, and was less expensive than renting a heavy-duty drywall lifter, which would have been another way of doing it.
Soundman--Modular-inside-out-ceiling--202--Raising-one-module--recording-studio-construction.jpg


The module raised into place. You can also see that, in this case, we added cleats around the top of the hole where the modules will be inserted, to ensure a better air-tight seal. You can't see it in these photos, but the sides and top edges of each module are coated with caulk, to crate a good air-tight seal. This is also critical for good studio isolation. Each leaf must be completely sealed, fully hermetic.
Soundman--Modular-inside-out-ceiling--203--Module-in-place--recording-studio-construction.jpg


All of the modules in place, except for the last one at the far end of the room, which is just being installed in this photo.
Soundman--Modular-inside-out-ceiling--204--All-modules-in-place-except-one--recording-studio-construction.jpg


The insulation is then installed in the empty bays under the modules, as part of the acoustic treatment for the room, with fabric below that to create the final visual ceiling for the room. The blue "tape" visible here is actually tough nylon packing strapping, used to keep the insulation in place. Note how the strapping is stapled to the sides of the framing, to prevent the insulation from touching the fabric below. If the insulation sags down and touches the fabric, it would create ugly bulges and bumps in the ceiling surface, but with the strapping done correctly there's a small gap between the insulation and the fabric, and the farbic ends up perfectly flat.
Soundman--Modular-inside-out-ceiling--205--Insulation-and-fabric-installation--recording-studio-construction.jpg


Another view of the room and ceiling, with the fabric nearly completed.
Soundman--Modular-inside-out-ceiling--206--Partly-complete-fabric--recording-studio-construction.jpg


One section of completed fabric on the ceiling, before trimming off the edges:
Soundman--Modular-inside-out-ceiling--207--Fabric-detail--recording-studio-construction.jpg


Wood trim placed at strategic places over the fabric, for aesthetics. The trim hides the staples that hold the fabric in place, and also the joints between adjacent pieces of fabric. Note that the fabric is carefully stretched taught, with no dimples, wrinkles, or other imperfections, then stapled to the framing above.
Soundman--Modular-inside-out-ceiling--208--Wood-trim-on-fabric--recording-studio-construction.jpg


Another view of the wood trim pieces, showing how the wiring for the lights is done. The wiring is completely WITHIN the room: there are no penetrations through the ceiling here. The wiring runs in small holes drilled sideways through the joists, to the rear wall where the distribution panel is. (This is also important: Do not cut holes in your drywall to mount electrical boxes! All of the wiring must happen inside the room, with no penetrations of the drywall. There is only one single penetration though the inner-leaf, to bring in the power feed from outside, to the distribution panel, and that penetration is done in a special way to maximize isolation):
Soundman--Modular-inside-out-ceiling--209--More-trim--recording-studio-construction.jpg


Detail of one of the light fittings, after installation on the ceiling. It is attached to part of the framing, just above the fabric.
Soundman--Modular-inside-out-ceiling--210--Light-fitting-detail--recording-studio-construction.jpg


The completed ceiling:
Soundman--Modular-inside-out-ceiling--211--Completed-ceiling--recording-studio-construction.jpg


Another view of the competed room, with happy musicians jamming away merrily, under the completed ceiling:
Soundman--Modular-inside-out-ceiling--212--Completed-room-with-musicians--recording-studio-construction.jpg



So that's how to do a "Soundman Inside-out Ceiling".


OK, but what are the benefits here? Is it worth it?

I have seen some people (even so-called experts) claim that there is no advantage do doing this, but they are not thinking things through, because the advantages are very real, and very clear. Their argument is that the ceiling ends up at the same height anyway, because the joists are in the same place, so there's no advantage. But in reality that is not true: the acoustic ceiling is much higher than the lower edge of the joists, and that's what matters most. The actual hard, solid, boundary surface of the room (the sheathing) is way above the level where it would have been for a conventional ceiling. You gain back all of the space between the joists. That would have been lost with a conventional ceiling, since it would have been above the sheathing, outside of the room, but with this method that space is now inside the room. In effect, your room is not several inches higher than it would have been, from the acoustic point of view.

The visual ceiling is also a bit higher than it would have been. With a conventional ceiling, the layers of sheathing hang down below the joists, do the final visible surface would be a couple of inches below the joists. But with this "Soundman Inside-out ceiling method", the final visible ceiling is the fabric, which is stapled directly to the joists: so you also gain back the thickness of the sheathing: the room looks higher, visually, and it is higher acoustically.

But there's an additional benefit: With a conventional ceiling, the surface is drywall: that's a terrible surface, acoustically, for a studio ceiling. It will need some type of acoustic treatment on it, which will take up even more space. For example, you typically need at least 4" (10cm) of insulation on the ceiling of most control rooms, and possibly 6" (15cm) or more. With a conventional ceiling, you would need to hang that below the drywall, so your visual ceiling would be even lower. But with an inside-out ceiling done my way, that treatment is already there! The insulation goes above the fabric, between the joists, and does not extend below the joists at all! So the final visible surface of the ceiling is the fabric, which is already higher than the drywall would have been for a conventional ceiling, and the acoustic treatment is already there, built-in: no further treatment is needed.

There's one additional benefit: All that framing up there acts a bit like an acoustic diffuser, breaking up or scattering the sound that hits it. So that's a bonus, on top of all the other benefits.

Thus, it's a win-win-win solution: You get a higher acoustic ceiling, and higher visual ceiling, and built-in treatment that is hidden from view.

This is the best solution if you want to isolate your room and also get the best possible acoustics. The only drawback is that it is more complicated to build. But the benefits are very real, and very much worthwhile.

Here's a photo of a different room done the same way. This room is larger (this is a live room, not a control room), the joists are even deeper, the modules were raised a bit higher, with the drywall ending up slightly above the top of the joists, so the benefit is even greater here. The final hard boundary of the room here is about 9" higher than it would have been if I would have designed the room with a conventional ceiling.
FCAUS--LR-ceiling-done.jpg


Finally, here's another way of doing an inside out ceiling for a smaller room, such as an isolation booth, which can work in some cases. The entire ceiling was built on the floor, then raised up using lots of heavy-duty manpower(!), and slid across into place, over the inner-leaf end wall. The outer-leaf end wall was then built. This method only works if you have no outer-leaf wall yet, and you have plenty of space beyond the inner-leaf wall to maneuver the ceiling... as well as plenty of strong people to do it!
NLRSA-Inside-out-ceiling-lifted-into-place.jpg


- Stuart -
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John Steel
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Re: How to build an "inside-out" ceiling.

Postby John Steel » Tue, 2019-Nov-05, 14:34

Great 'How To' guide Stuart - thanks for posting it. Are there any other photographs of the car jack lifting device please? Very ingenious!

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Re: How to build an "inside-out" ceiling.

Postby Soundman2020 » Tue, 2019-Nov-05, 18:57

John Steel wrote:Great 'How To' guide Stuart - thanks for posting it. Are there any other photographs of the car jack lifting device please? Very ingenious!
Your wish is my command! :)

Soundman--Modular-inside-out-ceiling--202b--Car-jack-mechanism--recording-studio-construction.jpg

That's another photo I found from that sequence: there might be more, but I think you can figure it out from there...


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John Steel
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Re: How to build an "inside-out" ceiling.

Postby John Steel » Tue, 2019-Nov-05, 21:18

Much obliged!


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