John Sayers' Recording Studio Design Forum Archive

I have a room with external entrance built above my garage that I have my eyes on for a multi-purpose audio/office room. Attached is a 3d sketch of dimensions and layout.

Some notes on how the room is constructed...
Room height is 8 ft. The outer walls of the room are 2x4 framed construction faced with stucco on the outside. The ceiling is 2x8 construction supporting a foamed flat roof. The floor is built up on top of the existing roof (flat-roof house with 2x12 ceiling joists), and is built with 2x6 joists cut down to follow the angle of the roof (slight grade to allow for drainage). 3 of the walls (all except wall w/outer door) are built on top of the parapet concrete walls that rise up 2 feet from the roofline around the house... exterior walls of the entire house are 8" concrete block, only the studio is framed. As such, the walls of the studio are not connected to the studio floor joists on those 3 walls. The 4th wall of the studio is built on top of the floor of the studio.

For the past few years, I have been doing research on this site and through other sources, and have narrowed my design priorities down significantly. I have decided against designing for full sound isolation because:
1) Cost and loss of space as a result of building room in room construction (especially with a bathroom already built, and implications of floating).
2) Mostly a quiet neighborhood, with only major sound issue out of my control being road noise (low frequency) from a nearby street, and occasional noise from neighbors since I am near the bottom of a bowl shaped topography, with neighbors higher up.
3) Multi-purpose functionality of room needed (office, guest room, and listening/recording studio)

Through significant reviews on this forum, I have set my sights on 2 primary strategies for acoustic design.
1) Sound isolation "lite" to minimize disturbance to neighbors, and of most mid-hi frequency sound intrusion
2) Dampening on floors, walls, ceiling.
3) Interior acoustic treatment - post construction and acoustic testing.

For sound isolation/dampening, I will be pulling up the subfloor to gain access to floor joists. Addtional blocking under walls of bathroom and outter walls as needed, acoustic cauking of all cracks, holes, insertion of mineral wool between floor joists, and then replacement of subfloor. Subfloor design will consist of 2 layers of OSB (or 1 layer playwood, 1 layer of OSB) with a layer of greenglue sandwiched between. Then 3mm acoustic pad, and final floor a 5/8" engineered floating wood floor. FOr most of the walls and ceiling, I am going to use existing drywall and add a layer of 3/4" drywall with greenglue sandwiched in between. Areas between the studio and the bathroom will have drywall removes, and mineral wool installed between 2x4 wall joists, and then 2 layers of drywall with greenglue in between (5/8" first layer, 3/4" second layer). Will have to live with a reducer between the studio and bathroom floor because of slight height difference, or tear up tile floors in bathroom...

Doors (outer and door to bathroom) with have commercially purchased sound dampening kits installed to add mass, and close gaps while still providing a functional door. Interior door is solid wood.... exterior door is foam core aluminum.

Windows will have custom fit plugs (2" soundaway mat) that can be inserted and removed when needed (couldnt sacrifice those wonderful mountain views...).

Acoustic treatment is TBD, but am looking at panels from http://www.atsacoustics.com. Listening location is about halfway between bathroom door and long wall with many windows.

I have started exploratory demolition to get this far, but thought I would post to gather any feedback and keep progress on the studio updated as I progress.

The main questions I have at this point are whether it would be worth the time, effort, and money to persue any type of additional floor isolation options since I am already planning on removing subfloor, and whether the additional acoustic value of mineral wool would make the costs of removing and replacing all drywall in walls and ceilings worth it (as opposed to leaving the pink stuff in and just adding a layer of 3/4" with greenglue).

"and final floor a 5/8" engineered floating wood floor."

Glued down or nailed...it's a rattle waiting to happen if it is not attached in some way.

I was planning on floating it with a 3mm pad underneath, although you are right... nailing it down or gluing ensures no rattle and would probably be best.

I just posted a new topic to elicit help on floating the floor in my situation. Here is the sketchup plan for the proposed floor layer structure. Is this a crazy idea?

Building an elevated room with want of some form of isolation is difficult, not crazy, just difficult.

Some things to consider:
Airborne Sound Insulation in Multi-Family Buildings


That will eventually lead to the reason I posted this link: rr219-Guide for sound insulation in wood frame construction.

I saw/read your other post that Rod and Glenn have been helping you with, so you are in qualified hands, there.

My reason for posting is so that you can have the information that can help you understand why not only are the additional joists you propose going to hurt you but why the existing joist orientation may already be prepared to cripple the project to some degree.

Attempting to lift a wooden floor above a wooden floor is still a wooden joist floor that has had the hard connections increased by 50 percent, based on your thinking in the documents you show.

Thanks so much for the info x. The paper on flanking transmission is a long one, but I will check it out. I have resigned myself to the fact long ago that I will not be able to eradicate flanking with a second floor structure and have adopted a "best effort where reasonable" approach instead. The isolation of joists option only came up in design planning because I already had to tear out all the material above the joists to expose them anyways. My original plan was to simply build the top portion (above the isojoist on the diagram) of the floor that added mass and dampening through a layer of greenglue and resilient pad under the hardwood flooring and call it "best reasonable effort". On the walls I was planning using RSIC 1 channels and 2 layers of drywall with greenglue in between. Now that I have opened it up though, I want to look at a broader range of options while correcting structural deficiancies. It has opened up the options in this thread as well as perhaps a room within a room design.

Another idea is to have the additional 2x8 dampened with the isojoists underneath... where it would be between the 2x8 and the 2x12 instead of above the 2x8 (under the floor structure). The challenge here is that the isojoists I have seen are 2" long and are designed to rest on a flat surface rather than another 1.5" joist. I considered adding a layer of OSB/Plywood for them to rest on, but now I have a mass-air-mass-air-mass 3 leaf issue between my garage and the studio. If I left the cavity between the 2x12's open (ie, no or very little insulation), would that be enough space such that the 3 leaf would not diminish the impact of my efforts?

Dampening through green glue is a strategy to lessen the effect of flanking noise in a room. Decoupling is aimed to stop it from entering in the first place. If this were your hobby studio, what would you do?

the GG will help with the resonant qualities of the drywalls and floor but its not really an isolator. if you cannot decouple the structure enough for your needs, consider decoupling the isolation walls from the structure using isolation mounts or neoprene, etc, and decoupling the ceiling and floor - isolation clips and hat channel/furring strips on the ceiling, damped membrane floor inside the isolation walls.

Thanks Gull -
Will consider all of those approaches at this point. It seems like the main challenge is going to be how much isolation or decoupling on the floor I can achieve and then work my way out from there. I have some structural concerns I am trying to work through in that arena.

Perhaps I should just build a vehicle elevator to park my cars in the room above the garage and build my studio below where there are concrete floors?

gullfo wrote:the GG will help with the resonant qualities of the drywalls and floor but its not really an isolator. if you cannot decouple the structure enough for your needs, consider decoupling the isolation walls from the structure using isolation mounts or neoprene, etc, and decoupling the ceiling and floor - isolation clips and hat channel/furring strips on the ceiling, damped membrane floor inside the isolation walls.

I have to differ, again, that these mounts are not designed to be able to sustain an isolation break from a light weight framed assembly that supports a lightweight framed assembly.

Granted I have not looked into them to much since I am well aware of how vibration moves through a structure from every connection.

Based on my ignorance in this area, can you help me to update my knowledge to get on board with this method? I admit to being a tad lazy, but if you can point me to a starting point that supports this method, I can most likely get through the rest, with as much humbleness as I can muster:)

Outside of that, what the OP is suggesting is an ill conceived plan.

Which mounts are we referring to? I don't think the 3mm pads will suffice but proper isolation mounts and clips will assuredly do the job. Since we're still discussing strategy and options and not technical specs just yet, we can be a bit abstract until we're all in agreement on structural approach and difference between floating a floor or floating the wall (my suggestion).

gullfo wrote:Which mounts are we referring to? I don't think the 3mm pads will suffice but proper isolation mounts and clips will assuredly do the job. Since we're still discussing strategy and options and not technical specs just yet, we can be a bit abstract until we're all in agreement on structural approach and difference between floating a floor or floating the wall (my suggestion).

The issue in general is that we speak of isolation in an upper wood framed area like it can be contained, sound wise. Sure, maybe it can, but it isn't like what the >buyer< thinks and there is limited information that supports most of what is said around here, except that it suggests....don't do it.

So why entertain it it?

If I have a handle on this, and I am pretty certain I do, we are talking here, and even in the other thread, about building a structure within a structure that has (1) no connection) and (2) is elevated.

This is not going to pass code. AND...let's consider the ability of this free floating room to move under seismic loading...some things should be stopped before they get to this point of having two or three threads about the same thing.

Here is what the flooring "layering" is going to look like... starting from the drywall hanging in the garage on up.

The plywood/osb with green glue sandwiched between on top of 2" of rigid fiberglass is mentioned in the new edition of Rod Gervais book, "Home Recording Studio, Build It Like The Pros". Gypcrete is mentioned as optional depending on weight allowances of the structure, and the method utilized a floating wall design using Mason Industries ND Isolators for the inner wall (room in room design).

One thing that was not clear in the book is whether this would require the use of WIC clips to tie the interior walls to the outer walls for stability. I assume yes, but not certain.

Also, why not just pour gypcrete on the entire surface and build inner stud walls on top of the gypcrete rather than only pouring to the sleeper stud and then having to isolate that stud from the wall assembly? With the mass of the gypcrete below the inner wall, wouldn't this have a similar effect on reducing flanking?

BTW - Below is also an update on the plans. No elevations yet, but getting closer...

the challenge with putting your framing on the gypcrete is the amount of pressure on the edge which will inevitably lead to cracking and/or short-circuiting the edge due to compression of the insulation. the overlap of the drywall to floor with sealing will ensure good isolation there.

Thanks Glenn. After discussing with the applicator and checking a dozen forums on Gypcrete methods, certainly the "studs on top of gypcrete" method doesnt have many advocates.

Going to move ahead with laying the gypcrete flush with a 2x4 sleeper (sub sill), and probably caulk the joint where the sleeper meets the gypcrete for a backup in case of cracks.

Here is the updated floor levels, with the sleeper, Mason ND Isolators, and wall sill... it all lines up rather nicely with the finished floor. There will be a bit of give to the isolator which I will have to account for in building the door thresholds, but will tackle this in the field once the walls have been loaded down with the heavy door assembly and then drywall.

Finally getting a good start on the floating iso wall elevations. Here are the first 2. It is my first attempt at designing a frame for anything, so took me awhile to figure out what the heck I was doing, but Rod's book helped significantly on this concept. I started with most difficult 2 walls (they support the heavy door and window in between the control and tracking rooms). I havent calculated the point loads to determine the size of ND isolators I need in each location yet. Will do once all the walls are elevated in case there are any changes to the framing plan. Only 8 more walls to go...