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Discussion Starter #1
I'm trying to figure out how to build a 'room within a room' in my basement. Today's problem is the ceiling.


My basement is only 7' 7" (232cm) tall (concrete floor to bottom of ceiling joists) so I'm thinking of putting 2x6's as room-within-a-room ceiling joists between the existing 2x8's on 16" centers, with the 2x6's sticking down about an inch under the bottom of the 2x8's. The 2x6's would be suspended by the new stud walls on both sides.


The interior of the room will be 4m (13.19ft) wide. But there's a 6" steel I-Beam that is 9' into that room that runs the entire length.


I believe that 2x6 untreated spruce, on 16" centers, 14 feet long, can take 5 pounds of dead load. So that should be good for three sheets of 1/2 inch gypsum on RC (1.7 pounds per).


There are two problems

a) I have two 16" spaces between joists that I can't put a 2x6 into. But I think I can compensate by putting double 2x6's very close to the 2x8's on either side of that. The RC will have to span about 36 inches there.

b) there's no way to put a 14' long piece over that I-Beam. i.e. I can dream it, but I can't install it.


Can the 2x6 be cut in half (e.g. 7') and then screwed together perhaps with plywood on both sides ?


Also, I need to notch the 2x6 to a 2x5 over the I-Beam to give me clearance. Does anyone have an idea what that'll do to the new dead load for it over a 13.19' long span? Obviously I don't want to have the ceiling touch the i-Beam, and I have a living room above it.
 

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Have you researched the difference in STC of just hanging your RC on isolation clips attached to the existing studs versus building your room within a room? I would think 1 and 1/2 inches of drywall hung from RC on isolation clips would be about as quiet as you would need.


Just thinking out loud.
 

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Discussion Starter #3
Hi BIGmouthinDC


As you describe, a wood floor, over 2x8's, with two layers of gypsum on battans right under the floor, then fiberglass insulation, then RC, then two layers of gypsum, should give an STC of around 60.

However, with the iBeam, and a furnace right outside the room making between 50db and 80db, and various other flanking issues, I'm not convinced that I'll get anywhere near the isolation I'm looking for without decoupling.

I'm in a townhouse, so I'm worried about noise getting out of the room, particularly bass.

I'm also worried about the load on the 2x8's. Since I also want to put some gypsum under the existing floor, and there's lots of stuff in the living room (14" bookcases down both sides and brick fireplace and ...).

Seemed to me that the easist way around both issues would be to suspend the new ceiling on some other joists.

Home depot sells 2"x6"x14' for $9.50 Canadian. I'd need 12 of them. That's only a couple hundred more dollars for the project.

My motto is do the best you can, and if it fails in the end well it's as good as it could be given the building.
 

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Quote:
Originally posted by BasementBob
I'm trying to figure out how to build a 'room within a room' in my basement. Today's problem is the ceiling.Can the 2x6 be cut in half (e.g. 7') and then screwed together perhaps with plywood on both sides ?


Also, I need to notch the 2x6 to a 2x5 over the I-Beam to give me clearance. Does anyone have an idea what that'll do to the new dead load for it over a 13.19' long span? Obviously I don't want to have the ceiling touch the i-Beam, and I have a living room above it.
Complicated post. To give others a visual they can look at Ted's papers here


In the cases where you need to cut your 2x6s I would just make my own micolamb (sp?) out of 3/4" plywood. I'd (gorilla) glue/screw 3 or 4 of them together.
 

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Discussion Starter #5
Thanks Scott.


Ted's pictures are exactly what I had in mind. I think I've been to that website more than a year ago. And this week I sent Ted a 'contact Send a quick comment' asking him about if his new joists touched his new I-beam or not.


I'm still considering just sticking RC to the bottom of the existing joists as BIGmouthinDC mentioned, because it's a lot easier/cheaper to build, and easier to stuff insulation into. But I'm leaning towards what I opened this thread with.


For the joined joists, I know I wrote 'screwed' together. But what I was actually thinking of was 8' x 5" of 3/4 inch plywood on both sides, woodglued, with 16 bolts (8 top and 8 bottom), with large washers. This would cover both the join, and the 5" thinner spot. It's much easer to fasten bolts when working on a ladder than screws, and they'll probably hold better too. Since the original spruce 2x6 is about 1.5" thick, and two pieces of plywood are about 1.5" thick, I guestimate that it's about the same strength, particularly with glue and top and bottom bolts. I think it would be weaker if the bolts only went down the middle.


But there's no stats I've found to cover that construction's load. I've heard of 'engineered beams' and 'engineered I beams' but I've never used them, and I suspect they'd come preassembled, whereas what I'm considering is basically to assemble them in the basement.
 

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Discussion Starter #6
Hi BIGmouthinDC


I re-read your post. I think I missed the words 'isolation clips' the first time.


I think you mean things like
http://www.pac-intl.com/pdf/comparrison_booklet.pdf


I haven't costed these out. But the advantage is that the supplied examples show that they only attach to the ceiling joists every three joists (which is more than the 36 inches I mentioned), which certainly solves my two-joists-full-of-stuff problem.


Are there any other isolation clips you were thinking of ?
 

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Discussion Starter #7
Spring Hangers are also interesting. Apparently they're very good with low frequency isolation.

http://www.kineticsnoise.com/architectural/icw.html

http://www.kineticsnoise.com/archite...icwinstall.pdf

says "... in the low frequency range from 25 to 100hz not included in the FIIC or FSTC data, the 1/3 octive band analysis indicates an average reduction of approx 7db per band for the FIIC and 7db per band for the FSTC when compared to the same ceiling isolated with RC-1 channel."

http://www.kineticsnoise.com/arch/pdf/icw.pdf

"Maximum natural frequency of 4.4 Hz under lightest typical load conditions.

STC 76, IIC 62 with Model ICW attached to Parquet Floor, 1-1/2†Concrete, 5/8†Plywood, 3-1/2†Insulation, ICW Hanger, 2†x 10†Joists, 2 layers 5/8â€

Gypsum Board."


That ought to do for ease of installation and noise, except for the weight concern.
 

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The clip I was thinking about here:

http://acousticalsolutions.com/produ...tion/clips.asp


After thinking about this some more I can't recall where seeing a clip for RC channel (the link is for standard hat channel) but I'm sure it's out there.


I'm not certain I understand where this steel beam is and why you would need to cut all your joists in half. Can you describe further?
 

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Discussion Starter #9
BIGmouthinDC wrote
 

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What would it take to just sister additional material to the sides of the existing joists and remove the steel beam?


Also, what were you planning to do with that beam hanging down below the bottom of your planned new ceiling? Box it?


Another thought I had is whether or not you have done any testing of the party wall sound transfer. Stick a couple of sub-woofers in the basement as is and crank them up. See how much travels next door to know how big a problem you are trying to overcome.
 

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Discussion Starter #11
BIGmouthinDC wrote



That's not possible. The existing 2x8's are not continuous across the entire spance. They stop at the steel I-beam in the middle. At the i-beam they're sort of beside each other, offset by 1.5", both sides still on 16" centers. So instead of being 19' long, they're 10' long and overlap at the i-beam. Running new long ones, probably two 2x10s for every existing 2x8, and supporting the entire house while I remove the i-Beam would be very expensive. It would be cheaper to move.


Hmm. You've given me an idea. If all I'm left to be concerned with is load, I could sister additional material to the existing 2x8's, and then use the kinetic's icw springs. Sounds like overkill. I'll wait until the Building Inspector tells me how much load my existing 2x8's can take before I start gluing 2x6's or 2x4's to the sides. Either way, this could work. I'll have to find out how much the icw's are.




Yes. The box would be supported by the 2x6's, attached to RC, and would not touch the i-Beam. The box would be made of 2x2s, and have 2 layers of gypsum attached to it. I'm planning on putting polycylindricals over that for difusion, and a fake 'box' for room symetry, but that's another thread.




The walls are 8" thick poured concrete in the basement, which should be fairly good. But upstairs I can hear his television through the probably 4 layers of 5/8 gypsum firewalls. The previous occupant (a nice old guy) said that he never heard me, but I could hear him snoring at night. The current guys listen to their sterio a lot.


I got a bit of a scare the other day when I had a couople of friends over and they turned my cheap/temporary 5.1 sound system up to what they considered to be a reasonable level. My little 150w sub in the empty basement was playing at 90db (radio shack sound meter at 15'), and it was very loud upstairs (through two layers of floor chipboard and carpet). It was louder upstairs than I listen to television with.


A good chunk of the isolation that I want is from the furnace that's also in the basement. In order to get the airflow CFM that I want, I have to run the furnace in fan-only mode (no heat, no AC). And in that mode it makes 50db. So anything that isolates the room from the joists I think will help. Walls are easy. I've got ideas, but not conclusions, about how to solve the floor, the door, and the hvac ducts. But that's another thread.
 

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Unless someone already mentioned it above, try searching for "garage home theater" posts on the forum. A few have built rooms inside their garages, and have detailed the process.
 

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Discussion Starter #13
Hi CZ:


I think this is more of a Basement thread than a Garage thread. Were I to build a home theater in my garage, for example, I'd be more worried about the outside walls than the ceiling. The ceiling in my garage is 10' up in the air, and has only a roof above it (no living space), so it's more of a structural problem than a decoupling problem. Building things that don't fall down is easy. I wouldn't be woried about noise going through the floor at all (either in nor out). But I would have to solve air conditioning somehow, and that would be very tricky with my current home. Heating, provided no one consumes oxygen, can be solved with electric heaters.


Nevertheless I'll search for "garage home theater" and give them a read. :)
 

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Discussion Starter #14
I realized two things last night:

a) I also have to take into account the increased load on the steel i-Beam. It's only 6" and it's also holding up the rest of the middle of the house (2 stories of load bearing wall is on top of it).

b) that the original '2x6 between the 2x8' that I started this thread with is more decoupled than springs (i.e. better if doable). And instantly solves the load on the i-Beam problem.
 

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OK so you'll slice the joists in half. Slice an inch off the bottom. I'm not certain how much of a splint you'll need to sister on to make them load bearing. You might want to splice a 6+ ft piece of the same material notched but not sliced on both sides and use some serious mechanical fasteners.


Put the splices up in there first just resting on the I beam. Then put up each half. I'd put up all of then up first then build the wall under. You could keep the joists lifted with some temp 1x2 braces screwed to the existing joists. Once the walls are up remove the braces and lower the joists into position. That way you'll have more room to wrangle the two half joists and the splints
 
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