Inner Room Construction Questions

I am ready to build the inner room-within-a-room and I am trying to minimize costly mistakes, some of which have already occurred. Current Situation It is a one room space to be used as a mixing/overdub space. Mostly acoustic, worldbeat and voice. No Led Zepplin drum recording. The exterior dimensions are 29 ft x 20 ft with a cathedral ceiling having a 14 ft height at the ridge beam. The interior ceiling slopes down at a 60 degree angle to 9 ft high walls. All walls are 6.5" thick SIPs (Structural Insulated Panels) and the ceiling and floor are 10.25" thick SIPs. A SIP panel is a "sandwich" of 7/16" OSB with rigid foam bonded in between the 2 layers of OSB. Each panel is 4 ft wide and can vary in overall length up to 24 ft. In my case the longest panel is 14 ft. The SIP floor structure is mounted on top of nine 12" diameter concrete footings with 2x12 Pressure Treated (PT) boards running across, and bolted to, the tops of the footings along the 29 ft dimension. Each SIP floor section is 4' x 10' and lays across the PT boards. Each 4' section has a 2x10 embedded in each side so , effectively, I have 4x10 "joists" 10 feet long every 4 feet. Two floor sections are used to span the width of the building. Double LVL "Rim Joists" run around the outside edges of the SIP subfloor and down the middle along the length of the building. See "subfloor3.jpg" Note: SIPs are _terrible_ for use in studio/sound isolation purposes. Fortunately, I found Rod's book. Unfortunately not before I used SIPs for the structure. But Rod's book turned me on to GreenGlue. That and this forum saved me from disaster. All interior wall and ceiling surfaces now have 2 layers of 5/8" drywall with GreenGlue between each layer using the Corner Framing Detail and GypBoard Sequence as detailed here in the Reference section. This includes the 1/4" spacing with backer rod and acoustic caulk between every surface boundary. The SIP floor has an additional 2 layers of 1/2" OSB with GreenGlue between each layer. These OSB layers do not touch the exterior walls. (The effectiveness of the GreenGlue was really highlighted on the floor with the "before/after" walking/stamping exercise. What a difference as compared to just adding OSB or plywood!) This structure is in my backyard which is about 1/2 mile /1 km from a major urban highway. Using a NADY DSM-1 digital SPL meter (and a Radio Shack analog meter) the typical outdoor noise level at rush hour is 60dB (C weighted, Slow). This is an average over 2 weeks of taking measurements. Before the GreenGlue/double layer of 5/8 gypsum on the walls and OSB layers on the floor the interior noise level was only 3-4 db lower (DOH! Ouch!) After applying the GreenGlue/drywall the interior noise level is an average of 12 dB (C) lower - about 47-48 dB (C). At the "A" weighting setting the Nady DSM-1 reads an interior noise level of 34 dB (A) with an exterior reading of 47 dB (A). The sound isolation would be even better if I had used laminated glass rather than vinyl framed residential windows (Double DOH!). Inner structure plan I am planning on building the inner walls and ceiling using 2x4 construction 24" OC. The walls and ceiling will be finished with 2 layers of 5/8" gypsum with GreenGlue between the 2 layers. Regarding the windows: There are times this space will be used as a Tai Chi studio and it would be nice to have fresh air/be able to open the outside windows. I am planning on using 1/2 inch thick laminated glass for the inside windows. In order to get "reasonable" sound isolation I plan on building the corresponding interior window frames that is 1.5 inches wider than the exterior windows on all 4 sides. The interior wall/window frame will have a 5/8 or 11/16 inch deep pocket cut into the wall. My plan is to embed a rubber seal around the window frame. The 1/2 inch thick laminate window will have 3 holes drilled through the glass (all 4 corners and one in the middle of each side ) to accommodate stainless steel fittings from cl lawrence (think large "wing nuts" ) that will screw into the wall squeezing the window perimeter against the rubber seal. I will also mount metal hand holds on either side of the glass so I can loosen the "wingnuts" and remove the glass when I want to have access to the outside windows. The weight of the 1/2 inch laminate windows will be around 85 Lbs. Doable for me. This is the best I have come up with so far that will allow for two opposing requirements. 1. What final interior dimensions/room ratios should I go for? Rod's book lists 6 common ratios used in studios. I want to have as large a space as possible yet stay close to "good" ratios. 2. I want to mirror the cathedral open ceiling space that I currently have. This means all walls and ceiling will be completely separate EXCEPT where the inner room ridge beam will be attached to the jack post holding up the exterior ridge beam (pix below). I plan on using a Simpson extra wide connector and line it with neoprene rubber to act as an isolator of sorts. I am not concerned with "flanking " noise as the building is a free-standing building. Will I lose too much in noise isolation if I connect the inner room to the outer structure at these two points? See "inner ridge beam.jpg 3. Half of the space has no windows and this end is where I plan on locating my mixing area. I plan on using 703 type absorption on the walls and corners at this end of the room (and throughout the room as needed). Should I angle my interior walls in at this end or just leave them straight and apply trapping. I was listening to an AES talk from this past October in San Francisco and the "pundit's" comments were to leave the walls alone and just apply appropriate absorption. The most wall angle I can use in the space is 11 degrees. Is this enough to make a difference? Or should I just leave it alone and use the trapping/absorption? Fresh air is being handled by a FanTech SHR 2005. A/C and heating will be supplied by the Mitsubishi "Mr. Slim" M series wall mounted unit. Thanks so much to knightfly, Aaronw and sharward for all their effort and insight on this forum. It has been incredibly helpful and encouraging. Also, thank you Rod for writing your book!

No opinions/suggestions? Did I give too little info? Too much info? Bad personal hygiene? Enquiring mind would like to know...

Happy New Year, Jeff! 8) Your questions #1 and #3 are about dimensions, so even though it may seem to contradict the advice we typically give to "keep it all together in one thread," you may want to post those questions in a new thread onthe "Studio Design" forum. You're likely to get more action there for that. Question #2 -- dealing with your ridge beam being in the way of framing a "room within a room." That's really unfortunate... :roll: ...Your challenge reminds me a bit of the one covered injshulze's "Need help with isolation between floors" thread -- he's got some steel columns going from floor to roof and he'll need to build around them. You might be able to have some kind of resilient seal around it, much like you might do with a pipe or duct penetration. Perhaps the solution is something like wrapping it with a thin layer of soft, closed cell foam, along with the use of backer rod and acoustic sealant. Note that I mean for this to be done only where the beams and the inner leaf walls/celing intersect -- not along the entire beams. (That beam may look nice with some stain on it when you're all done... :roll:) Go with that for now, unless someone has a competing idea or thought. Before you construct it, though, post a detailed cross-section sketch of what you intend to do, as I don't want to lead you down a path by my irrelevant lunatic ramblings. :twisted: Hope that helps. If it doesn't, double your money back. ;-) --Keith :mrgreen:

Happy New Year to you too Keith. (I guess taking that shower helped elicit a response :wink: ) I will follow up on your suggestion for posting questions 1 & 3 in the Studio Design section. Re: Question 2 Quote:" Perhaps the solution is something like wrapping it with a thin layer of soft, closed cell foam, along with the use of backer rod and acoustic sealant. Note that I mean for this to be done only where the beams and the inner leaf walls/celing intersect -- not along the entire beams." I will not be attaching any wall or ceiling to the exerior LVL Ridge Beam or directly to the LVL Cross Beam. All inner leaf and ceiling will be detached from the exterior building shell Except for two Simpson connector locations on the Jack Post (approx 12 inches down from the top of the Jack Post) where my 2 inner room ridge beams would hang. The other end of each inner ridge beam would attach to the detached inner gable wall framing at either end of the building. The Jack Post is situated at the middle of the pictured LVL Cross Beam supporting the exterior structure's Ridge beam running the length of the building. My question was concerning how much I would be "losing" in sound isolation by having my inner building frame connected to the outer structure at these two points of contact where the two Simpson connectors attach to the Jack Post. I would line the inside faces of the Simpson connectors with neoprene rubber for some form of isolation. The existing Cross Beam will be isolated from my inner walls using backer rod and acoustic foam (and I do plan on painting/staining/adding veneer to that Cross Beam when I am done with construction). May the Force be with you for finishing up your own project. Following your story, guitardad72 Marc's progress and others here have been very helpful and encouraging. These projects take a WHOLE lot longer than one first realizes. Or is it that my money tree farm is not producing fast enough so I can hire Rod to do it in a fraction of the time?? :D