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Old 25th June 2019
Here for the gear

Originally Posted by Tommy_M View Post
Hi folks,

I'm in the process of designing a music studio as a second floor addition over my two door garage. I'm looking for advice in a few areas. I've read Rod's book so have some fundamentals background, but little in practical experience.

A little about the project..

The garage is about 20ft x 20ft. I'm building directly over an existing garage, so the room above will have the same dimensions. I'm currently planning a combo room in that space for mixing and recording a full band with one isolation room and a closet for storage. My big concerns are neighbors complaining about noise in the middle of the night from a blaring organ and drums. The closest neighbor is about 50ft from the garage. Inside I want to make sure it's a room suitable to record as well as mix. See attached for a preliminary drawing w. no details yet on construction.

A few things I'm worried about:
1. I don't believe that supporting a concrete slab on the second floor is practical (although maybe I'm wrong on that..) I've considered floating the floor on something like the Aurolex U-Boats, but Rod's book is pretty specific in noting that this likely won't sufficiently decouple and could create low frequency resonant issues. If I don't float the floor, I'm thinking I could do 3X layers of 3/4" OSB with green glue between each layer. Noise directly below isn't necessarily a big issue, but I'm worried about it escaping below and out the exterior walls to the neighbors. On the topic - does flanking only matter when you are worried about someone being within the structure (aka a person on the first floor of the garage in which they could hear the walls carrying the vibration? Or would flanking not be of a big concern when thinking about a neighbor within a house 50 ft away? Which method (floated vs simple dense floor) do you think would work better?

2. For the walls, I was initially considering building a room within a room - a 2 leaf system with exterior walls made as such:

Lap Siding - Housewrap - 3/4" OSB - Green Glue - 3/4" OSB - 2x6" Studs w Insulation

and Interior Wall made:

2x4" Studs w/ Insulation - 5/8" Drywall - Green Glue - 5"/8 Drywal

Whether or not the interior wall is helpful "I think" depends on what I'm doing with the floor. It's my understanding that if I don't decouple the floor in some way (which again, I'm not sure is possible) then the flanking issues through the floor will make the isolation achieved by the interior walls meaningless. In that case I may be better off ($s and space) by getting rid of the interior wall and moving the 2 layers of drywall to the interior of the exterior wall. Thoughts on these two approaches and the dependence on the floor?

Another question I had was on windows. I can't go about putting in an addition without windows (or at least something that looks like a nice window) without my wife cutting off all funding to this project. Let's say that it makes sense to do a double wall assembly. Does putting real windows in create a major weak point? Or maybe I can fill in the window with mass equal to the same density as 2 layers of OSB like the rest of the exterior and be sure to make it airtight and it won't make any difference. Thoughts?

Thanks for the initial guidance folks!
Have been searching for solution for this exact scenario and just found your post. Did you end up with a solution for the floor? I'm building a house and designing a studio over a detached garage so it won't even share a wall with my home. I play the drums so still plan on isolating using a double-wall system for both my neighbors' sake and for isolation between the control room and live room. Just need to know if going through the expense without decoupling the floor from the structure. The one unique part is that the garage isn't built yet so I have ability to change structural and system make-up of both the ceiling of the first floor garage, and anything above that.