Author Topic: Room within a Room  (Read 7649 times)


  • Guest
Room within a Room
« on: December 29, 2006, 07:44:19 AM »
The search feature for this fourm doesn't  seem to work for me so I don't know if this topic has been discussed in detail.  I have been doing some research on the subject of soundproofing and understand a lot of the options including all of the materials being sold by the moderator of this board.

I wish to "soundproof" bedroom in a condo for my mother.  The bedroom has 9' foot ceilings. The condo is a bottom unit with concrete slab floor, subfloor and carpeting  Tearing out the existing walls is not an option and given the fact I can afford to lose some headroom and square footage I am leaning toward building a room within a room. I considered the resilient channel option but I am inclined to go with what is the more effective solution, albeit more expensive.

These are some of the things that are passing through my head:
1. Stapling MLV on the Existing walls and ceiling prior to framing new room.
2. Need to address firesprinkler head that potrudes from ceiling about an inch or two.
3. Need to address Ceiling Fan.
4. Need to address Code and Building permits issue
5. Need to address how best to frame floors, walls and ceilings.
6. Ceilings are of a particular concern since obviously limited space exists once walls are stood up, plus the fact rafters need to attach to new wall and not the existing ceiling structure.

Any opinions on any of these items would be appreciated.


  • Guest
Re: Room within a Room
« Reply #1 on: December 29, 2006, 10:34:08 PM »
You have a lot of issues.

First of all, it is a bad idea to leave the drywall on the existing wall, then frame up your new walls.  You'll be defeating a lot of your purpose.  You'll have what is known as a 'triple leaf' wall, with bad cavity resonances and won't come anywhere near the soundproofing potential of a double wall.

Addressing your thoughts (assuming you go with 'room in a room'):

1. MLV.  Skip it.  MLV works best when you can hang it as a limp curtain, not when it's up against another surface. 
2. Obviously, if you significantly lower the ceiling, you're gonna have to adjust the sprinkler.  Call a plumber and see what kind of number he gives you.
3. You can turn you existing electrical box into a junction box (w/ cover) and run a wire to a new electrical box on the new rafters.
4. Building permits aren't too sticky, but a 'room in a room' raises code issues with fireblocking.  More often than not, the inspector will demand changes that nullify any benefits of double wall construction. 
5. Framing is no different from normal construction.
6. It can be a little tricky.  You have to frame, insulate and get some drywall on the walls, then hang the new rafters w/joist hangers, all the while making sure you walls stay square and plumb (and don't fall down on your head).

Well, with that, here is the advice I give most people...

If I were you, I'd tear off the existing drywall on the walls and ceiling, convert the walls into staggered stud walls by adding 1X2/2X2 furring strips to the plates and edges and adding new studs.  This way you'll only lose 1.25/2.25" of space vs. 4-4.5" for a double wall. Insulate the wall and joist cavities (after doing some sealing, of course) - R-19 for the walls, R-30/R-38 for the joist cavities.  Then, double drywall on the walls, with good sealing, and hang the ceiling (also 2X drywall) on isolation clips and hat channel.  Seal up the edges and seams, mud, tape, paint, and you're in business.   

This will give you really good soundproofing for the amount of space lost.

I don't know what floor your mother lives on, but keep in mind that a lot of sound is coming up through her floor.  Her downstairs neighbor's ceiling is directly attached to her floor joists.  You might have to do something about that.   

But, if, as you said, tearing the existing drywall off is "not an option", then maybe you should simply double up the existing drywall using Green Glue.  Most of the issues you're facing would go away if you went with the simple option. 


  • Guest
Re: Room within a Room
« Reply #2 on: December 30, 2006, 01:03:10 AM »
Thanks for your feedback. It is difficult to know what is best when there seems to be so much contradicting information out there, especially from the people selling the products. I read two articles from Journal of Construction (or maybe Fine Homebuilding) that talked about sound control and in both cases the contractors were utilizing MLV.

This article from a seller of QuietRock has a different take on MLV.

Anyway I am still chewing on all the data including your suggestion regarding a staggered wall with furring strips. I had read about staggered walls where the wall plates are 2x6s and the studs are 2x4s for new construction. But your suggestion is an interesting twist on that for existing construction.

I suppose we could try to get approval from homeowner's association to yank the drywall. So do you think your approach is better in terms of sound control than the use of furring bars (or alternative types) assuming loss of square footage is not too much of an issue?.


  • Guest
Re: Room within a Room
« Reply #3 on: December 30, 2006, 05:51:43 AM »
I just watched on the website the CBS quicktime video where they used QuietRock drywall for the walls after tearing out the carpet padding the guy was using instead.

If you watch the video they take a decibel reading from outside the house before and after.  The before video shows the instrument reading of 73 decibels although they claimed it varies from 75 to 80 decibels. 

After the work they showed the meter at 63 decibels which they claimed at the end was almost a 20 decibel drop. If you go by the instrument reading that they showed on camera it may have been only a 10 decibel drop.

While you don't see all of the details, it appears that they are using 1 layer of the QuietRock with standard insulation in the stud cavities. Presumably the exterior has plywood sheating. I would imagine the STC rating of the room probably didn't exceed 47 which seems rather weak for a practice room.

I just thought it was odd that they ended up with a 63 decibel rating after all of that. That certainly wasn't a "dramatic reduction" in the noise level as they claimed..


  • Guest
Re: Room within a Room
« Reply #4 on: December 30, 2006, 09:09:17 PM »
Well, my approach certainly isn't perfect and won't get you the ultimate in sound reduction, but it's pretty good.  I've found it's sort of a 'quick and dirty' way to construct a sound wall; it doesn't require any special techniques or materials, doesn't get you in trouble with the building inspectors (after going to all the trouble to build a double wall, it is very discouraging to have an inspector 'ding' you and make you change it), and doesn't eat up a lot of floor space. 

And if you're planning to add new walls anyway, I doubt the homeowner's association will have too much a problem with tearing off the old stuff, as long as the studs aren't exposed for too long - fire code violation.  Drywall comes off quick.  You could tear down a large bedroom and be ready for insulation in an hour or two.  You might get a little dusty, but....

Yeah, avoid Quietrock/Supress drywall products.  They are massively overhyped & overpriced.  You can get the same performance by using 2 layers of 5/8" type X drywall and a layer of Green Glue in between.  For about half the price.  It's a lot more fun and convenient to apply it in the field.

I have seen the video you mentioned.  They applied the drywall right to the studs, which is a bad idea.  If they had used my technique and had a staggered stud wall between the drums and the old lady, the decibel reduction would have been much higher.  However, if they'd converted the walls, they hardly would have needed expensive Quietrock....

I don't really have a problem with MLV, but people seem to think it's some kind of 'magic sheet' that will solve all their noise problems.  It isn't.  Unless you use it correctly - hanging as a limp curtain, not in contact with any other rigid surface, with all seams caulked and taped - all it does is add 1 lb/sq. ft. to your walls (equivalent to 1/4" of drywall).  And at $1.50 per sq.ft. ($48 per 4' X 8' sheet) it's too expensive to buy and apply incorrectly.  It's much cheaper and more effective to buy another sheet of drywall (at $8-10) and increase the mass that way.


  • Guest
Re: Room within a Room
« Reply #5 on: December 31, 2006, 01:50:05 AM »
You said,
hang the ceiling (also 2X drywall) on isolation clips and hat channel.

I wasn't sure from your recommendation whether you are saying I should install new ceiling joists to the newly created wall system or not. If I use the isolation clips and hat channel on the ceiling it seems to me there isn't a need to tear out the existing drywall from ceiling.

I was also thinking if I was to install new ceiling joists there wouldn't be a need to tear out the ceiling drywall. However, I suppose there may be a building permit issue with new joists.

Thanks again.



  • Guest
Re: Room within a Room
« Reply #6 on: December 31, 2006, 11:24:32 PM »
Installing new ceiling joists would actually be better and cheaper than the isolation clips+channel method.  The best would probably be hat channel on the new joists (hat channel is cheap).  If the room has enough height to spare, that is the method I'd use.  The joists aren't carrying as much load as regular floor joists, so they don't have to be as deep.  2X6's would carry the weight of double drywall, no problem, and you might be able to get away with 2X4's and preserve most of your headroom.  Ask your contractor/architect to calculate the necessary lumber to carry 6 lbs/sq.ft. with deflection of 1/180 of the span.

I usually put the drywall on the walls then bolt a 'rim board' to all four walls and hang the new joists on the rim board with joist hangers (makes sense, huh?).

If you go with staggered stud walls, since the wall cavity if closed up, there's no code issue with dropping the ceiling in this way - it's done all the time in bathrooms, closets and hallways.  If you go with a double wall, there is.  If, hypothetically, an electrical fire started in the wall, nothing would impede it from moving up the wall, into the ceiling cavity you've created and quickly taking the building with it.  It would act as a natural chimney.

You seem hesitant to tear out the drywall.  In order for your soundproofing to be effective, you need to fill the whole cavity with insulation.  And it is not a good idea to have a resonating panel inside a sound partition.  It will hurt performance, by 10-20 dB.  I don't really want to give you all this advice and have you go to all the trouble to get a disappointing result - one that might be unfixable.  Wiser to do it right the first time. 

If you're absolutely dead-set on keeping the old stuff, have your contractor make a series of holes (with a 4"+ hole-saw) and try to get a good amount of fiberglass insulation in the cavity.  The holes will allow the sound to bounce around inside and be absorbed by the fiberglass.  The more holes you make, the better it will work.  But it's infinitely easier to just tear the whole thing off - ask the guy who's gonna be doing the work. 

Soundproofing is very detail-oriented and you can really ruin your efforts with shortcuts, even well-intentioned ones.  Fair warning.