Questions on Inner Room construction. Please advise.

This is my first post so please excuse any mistakes or omissions I may have made. I've tried to provide as much relevant detail as I could concerning my questions. I appreciate your input and advice. Overview I originally started out finishing my attached 1 car garage with the intention of following John's studio in a shipping container design. The garage is 22'6" long by 10'6" wide, with a 7'5" ceiling. But, had I done this I would've been left with a very small control room and a very small recording studio for what I had truly hoped to be able to do. I wanted enough room to comfortably cut a live band if needed. I live in a bi-level and luckily the way my downstairs is situated to the garage, allowed me to use the large family room as the control room and utilize the entire garage as a tracking room. The family room and the garage are separated by a laundry room, which also contains a sectioned off area that houses the furnace and the hot water heater. So this room acts, somewhat, as a sound buffer between the two rooms. At this stage I've beefed up the outer walls and have just taken down the garage door and bricked up the front. I'll provide more details in the next few sections. HOW LOUD are you I'm not worried about the neighbors as far as making noise that will be a disturbance. Even when I had the flimsy garage door up, I cranked up a stereo system in the room, roughly about 100 dB in level, and outside there was only a small amount of bleed, nothing that I forsee as a problem. My main concern is stopping sound from coming into the tracking room. The street, though not overly busy, does get its fair share of traffic passing by. Other than the occasional cars passing by, it's a suburb and is fairly quiet, especially at night. Details Construction is underway. The main room I'm concerned with right now is the garage (tracking room). It is 22'6" long and 10'6" wide. Three of the four walls are outer walls and the lower 3 foot of the wall is the solid concrete foundation and the upper half (4'5")consists of the outside asbestos shingles, which sit on 5/8" siding, which is attached to wood studs. The cavity of the studs is filled with insulation and was covered with 1/4" plywood. This was my starting point for beefing up the walls. To beef the upper par of the wall up, I covered it with a 1/2" sheet of celotex and then 1" (two 1/2" sheets overlapped) of plaster board. The garage door that was closed off was framed out with wood, covered with 3/4" particle board. Butted up against this board is 4" hollow cinder block on the lower half (4 ft.) and brick on the upper half, to match the exterior of the house. The floor of the garage is solid concrete and is in excellent shape, and has no water problems whatsoever so it's a dry space. Which now bring me to the inner room and what to do with it. I've read numerous posts and articles from this website and have learned a lot about soundproofing. I had originally planned on building the inner room with staggered steel studs with 2 layers of 5/8" drywall on each side, with the stud cavity filled with insulation. Being I don't have a huge space and want to preserve as much space as possible, I was going to bring the inner room walls in about 1 to 2" from the outer wall. I wish I had the more space to leave more of an air gap, I know 6" is usually recommended. Which brings me to where I am now. I had the steel studs and the drywall ordered already but haven't picked it up yet and can still cancel the order. The guy who bricked the front of the garage up is a friend of my Father and he charged us a very reasonable price for the quality work that he did. When he was doing the job he had suggested doing the inner room with 4" solid cinder block instead of the studs and drywall. He offered to do the inner room for $2,600, which brings me to where I am now. Will 4" solid cinder block work for an inner room. I do realize that the inside will need fairly extensive sound treatment to tame the hard surfaces. So my questions are: 1. Will a 4" solid cinder block inner room do just as good a job as standard framing and plasterboard construction? 2. Since I only have 7'5" of height from the concrete floor to the plastered ceiling, I really can't float a floor properly and everything I've read has said not to do it unless you can do it properly. I just don't have the height to properly float a floor. I was thinking of putting Pergo down over the concrete and leaving it 1/4" short of the inner rooms walls and then filling that with acoustic caulk. Is it better to just finish the concrete? And of I do the Pergo, will it cause any potential problems? 3. The garage ceiling is finished plaster and above it are 2 bedrooms. I've not overly concerned with sound bleeding to other parts of the house. I'm single and don't have to worry about disturbing other people in the house. My main concern with the ceiling is sound bleeding down from the bedrooms from the outside. Ex. car noise passing through the upstairs bedroom walls and coming down through the ceiling. I was thinking of putting two 1/2" layers of plasterboard on the ceiling, or 1/2" of celotex and a 1/2" of plasterboard. For the inside finish I was going to use the Owens Corning 1" or 2" black acoustic board. Being I have limited ceiling height, is there a better way to beef up the ceiling than what I plan on doing. Budget As far as budget goes, the most important thing is that the room does what I need it to do, which is to be super sound proofed. As long as there are alternatives that are within reason when it comes to price, I'll spend the money for them. My main concern is the inner room. If the 4" solid cinder block will work it would help out greatly as it will help speed the construction process. But doing it right is more important than the speed. No sense in putting all of this money out and not having the room the way I need it to be. I have to make decison on the inner room in the next 5 days as the guy who would be doing the brick work will be traveling for the following month. I appreciate any direction and advice that you can provide me. Thanks in advance!

Alfadog, Welcome to the forum, :D

Construction is underway. The main room I'm concerned with right now is the garage (tracking room). It is 22'6" long and 10'6" wide. Three of the four walls are outer walls and the lower 3 foot of the wall is the solid concrete foundation and the upper half (4'5")consists of the outside asbestos shingles, which sit on 5/8" siding, which is attached to wood studs. The cavity of the studs is filled with insulation and was covered with 1/4" plywood. This was my starting point for beefing up the walls. To beef the upper par of the wall up, I covered it with a 1/2" sheet of celotex and then 1" (two 1/2" sheets overlapped) of plaster board. The garage door that was closed off was framed out with wood, covered with 3/4" particle board. Butted up against this board is 4" hollow cinder block on the lower half (4 ft.) and brick on the upper half, to match the exterior of the house. The floor of the garage is solid concrete and is in excellent shape, and has no water problems whatsoever so it's a dry space. Which now bring me to the inner room and what to do with it.

When the term “outer wall” is used around here most of the time we are referring to outer leaf wall, which could also be interior. Have you seen the term triple leaf yet? As I understand above description and your plan that’s where you are headed, please correct me if I am wrong. See link: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=598 And make sure you read through the reference section. Both leaving an air space (insulation counts as air) in your existing 3 exterior walls and the hollow cinder blocks you’ve added where your garage door was will produce triple leaf which is less sound isolation than double leaf. If you fill those hollow cinder blocks with sand or concrete you’ll be better off.

1. Will a 4" solid cinder block inner room do just as good a job as standard framing and plasterboard construction?

Please see the STC Chart here: http://www.saecollege.de/reference_material/index.html Yes I’m guessing you’ll have better sound isolation how ever you will have more weight. Your existing garage slab may or may not be able to take standard framing weight. Weight of concrete is obviously more. You could be building on the edge of a slab not connected to foundation walls. You need to figure out what type of footing/slab/foundation you have before you consider the weight of your walls.

2. Since I only have 7'5" of height from the concrete floor to the plastered ceiling, I really can't float a floor properly and everything I've read has said not to do it unless you can do it properly. I just don't have the height to properly float a floor. I was thinking of putting Pergo down over the concrete and leaving it 1/4" short of the inner rooms walls and then filling that with acoustic caulk. Is it better to just finish the concrete? And of I do the Pergo, will it cause any potential problems?

Exactly, in general you would need 5 to 7 layers of drywall on wall to make floating floor worth it, then you would have to build it and not screw up. Also most building code states 7’ or 7’ 6” minimum for room height of habitable space. Pergo (laminate wood flooring) will be fine. Depending on how live you want the room to sound any reflective floor will do fine. Wood seems to be the preference, although it’s arguable. BTW I’ve just done my own research on installing wood flooring… it’s going to be more work, at least in my case then I thought it was. I got level issues, 2 slabs and a removed CB wall to deal with.

3. The garage ceiling is finished plaster and above it are 2 bedrooms. I've not overly concerned with sound bleeding to other parts of the house. I'm single and don't have to worry about disturbing other people in the house. My main concern with the ceiling is sound bleeding down from the bedrooms from the outside. Ex. car noise passing through the upstairs bedroom walls and coming down through the ceiling. I was thinking of putting two 1/2" layers of plasterboard on the ceiling, or 1/2" of celotex and a 1/2" of plasterboard. For the inside finish I was going to use the Owens Corning 1" or 2" black acoustic board. Being I have limited ceiling height, is there a better way to beef up the ceiling than what I plan on doing.

Have you looked into buying Rod’s Book? Drywall is more cost effective and gives more sound isolation than Celotex but some have used Celotex. More mass gives better isolation, 5/8” drywall is what most of us use. Green Glue although expensive is about the only other material used with drywall to improve isolation, especially on Ceilings where weight is an issue. Removing existing drywall on ceiling, adding drywall between studs directly to above floor, using a decoupled inner leaf ceiling via Resilient Clips or independently framed ceiling is the way to go. Sorry if some of my answers seem incomplete. :? Spend some time on this site, use the search feature and you’ll get some good ideas. Rod’s book is one of the best resources out there. :D Marc :twisted:

So let me make sure I have this straight. The bottom 3 foot of my walls are the solid concrete foundation. So the lower half of the wall is the first leaf? But, the upper 4'5" of the wall consists of 1" of plasterboard, on top of 1/4" plywood, that is attached to the wood stud frame of the garage, the cavity is filled with insulation, the other side of the wood stud has 5/8" plasterboard, and on this plasterboard the outside shingles are attached. So does this mean the upper portion of my wall is 2 leafs? If so, how do I build an inner room without creating a third leaf for the upper portion of the wall? Do I just have any inner walls built up against the existing walls? Thanks for the links, I checked them out but now I'm even more confused...lol.

alfadog wrote:

So let me make sure I have this straight. The bottom 3 foot of my walls are the solid concrete foundation. So the lower half of the wall is the first leaf? But, the upper 4'5" of the wall consists of 1" of plasterboard, on top of 1/4" plywood, that is attached to the wood stud frame of the garage, the cavity is filled with insulation, the other side of the wood stud has 5/8" plasterboard, and on this plasterboard the outside shingles are attached. So does this mean the upper portion of my wall is 2 leafs? If so, how do I build an inner room without creating a third leaf for the upper portion of the wall? Do I just have any inner walls built up against the existing walls? Thanks for the links, I checked them out but now I'm even more confused...lol.

Yup you got your walls existing leaf configuration correct. Adding mass to an outer leaf wall, where you can not add on the outside face is kind of destructive. Many on this forum have done it and taken lots of pics. For example let's take an interior wall, drywall both sides and for some reason you can not add to the outside face. On the inner side of the wall (which next to you'll be building an inner leaf frame 1" or more away from) you would take all the drywall off. Let's say the studs are 24" OC. You would cut new peices of drywall 23 1/2" wide and the hieght of stud cavity minus 1/2". Place them directly against existing outer layer of drywall, you will have 1/4" space all around to insert 1/4" backer rod and then caulk. Then use 2x? or 1x? cleats up against corner of existing 2x4 studs and new drywall to to hold these new "beef up" layers in place. This method has been done on ceilings and on all sorts of exterior walls. Look at Shawards thread (a mighty long read), Dan F or Andy Eade's for pics of this actually being done and more description. Sharward is using a lot of "beef up" drywall, like 4 to 5 layers and there is hardly any room left in the cavities of his existing (pre studio room) walls. Marc

Guitardad72, thanks for the clarification of that. I'm glad I asked because that is probably going to change the way I'm going to build the inner wall. Does this sound like a better solution? I asked the brick layer if he could put the 4" solid cinder block flush with the wall so its mass will be a part of the inner leaf, instead of a totally separate leaf. But, if I do this the upper 4'5" will be Mass/Air/Mass, and the lower three foot will be the solid concrete foundation with the 4" solid cinder block flush against it, making it a single leaf of just Mass. There would be no Air and no Mass for the lower 3 foot. So I would have Mass/Air/Mass on the top and just Mass on the bottom. Would that be a better option?

Alfadog, Well, yes that would be a better option presuming your existing wall surfaces are plumb on the inner side and you can somehow insure solid contact with no air space between existing walls and new blocks. BUT how much better is the question AND will it be worth $2,600 compared to other methods you could or could have use. One of the suggestions on this forum and in Rod’s book is, do not use unproven construction methods. The double wall MASS AIR MASS requires the 2 masses to be decoupled. Since you are talking about adding mass your existing inside leaf which is coupled to the outer leaf via concrete foundation wall below and 2x4 studs & plates, you would still have a lot of flanking (sound transfer between coupled mass). I really don’t know how much better off you would be, I could do some research and make a wild ass guess, others on this forum could make a quicker wild ass guess. BUT I would not want to spend $2,600 on a not suggested method when I was aware of other methods, similar or less in cost, however destructive they may seem that I knew would achieve better results that have been proven, of which I can see test data and be confident of expected results. You may even be better off as is when comparing the cost to actual isolation gained. Note I’m not an expert at all this, but I have studied a lot for known construction methods of my own room. (I say “known” because I’m currently dealing with concrete slab/footer which I did not expect). In order to make that 4” block wall worth it you will also have to match the isolation on the ceiling. You still got to figure out if your garage slab can take that weight on its edges. My guess is “don’t know” and I would not trust a guess with that much weight. With a 2x4 wall and sheetrock you “should be” alright with weight. If you do decide to tear down existing material from inside garage wall you may be able to recycle it. A few guys on here have taken existing drywall down, cut it out carefully using studs as a guide and reused the drywall in between studs as beef up on outer leaf. I don’t know about the celtox. I presume you are the person who installed all this, even though it would be difficult (I would not want to do this myself) think you can take it down the all the drywall and celtox with out destroying it? I realize you’ve put a lot of work and money into celtox and 2 layers of ½” drywall on the upper part of those walls. Maybe all you want to do now is properly take care of the ceiling to match the current isolation of your walls. If I were you before I spend $2,600 on 4” brick inner leaf I would: Buy Rods Book for less then $30, read it 2 or 3 times (don’t know anyone who has got everything on the 1st read) While waiting for the book, go through this web site and others, spend hours reading & studying. :? Marc

Hey Alfadog, I've been following this and, like Marc, I really don't consider myself to be an expert (to which the title above my avatar will attest! ;-)) I just wanted to "ditto" all of the advice and opinion given by Marc. He's steering you in the a conservative direction that makes a lot of sense to me. --Keith :mrgreen:

If possible, you should do a basic sketch of your existing wall, framing, mass layers, etc, then add your proposed changes so we can be sure VISUALLY that you're not going to hurt yourself by adding some of the mentioned changes - pictures are usually much less likely to deceive than explanations, since there are so many ways to interpret words... Steve