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Sound isolated drywall ceiling "hung" 10" below joists: How to?

post #1 of 25
6/22/09 at 1:09pm
Thread Starter 
In my basement I have 8' 11.5" between the concrete and the bottom of the floor joists. Unfortunately, I have a steel I-beam that holds up those joists that runs lengthwise through the area I want to put my theater in. The beam is 8" thick, and has a 1.5" thick sill plate on top of it that the joists rest on. Since I have some height to give up, my plan is to move the ceiling of my theater down below the steel I-beam giving me a lower but flat ceiling.

My question is, how do I do this and maintain the best possible sound isolation? I expect / plan to use isolation clips, hat channel, insulation, 2 layers of drywall and green glue. Is there anything else I can do to improve the sound isolation of the ceiling instead of just building a rigid structure ~10" thick that the isolation clips and the rest of assembly will mount to?

The room will be about ~14' x ~22' if that matters.
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post #2 of 25
6/22/09 at 3:03pm
trading 10" of ceiling height for sound isolation reasons when a room is unbuilt is a very bad decision. (because you can plan for traditional/proven sound isolation now)

please reconsider and work on ways of working the beam into the room. the easiest way if it really runs lengthwise is probably a coffered ceiling, therby hiding the beam....

you will be much happier with that ceiling height later, no matter what you believe today.
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post #3 of 25
6/22/09 at 3:21pm
I also agree - plan the beam into your design and keep the extra 10 inches of ceiling height.

You'll see that low ceilings are probably the number 1 complaint with basement theaters!

Since fill the joists with insulation, attach clips/channel, 5/8, GG, 5/8. This combo will give you excellent sound isolation without sacrificing your space.
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post #4 of 25
6/22/09 at 3:38pm
Thread Starter 
The coffered ceiling is an interesting idea I hadn't considered.
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post #5 of 25
6/22/09 at 4:24pm
Do you have a pic?

A lot of us build soffitts to hide beams/HVAC/plumbing.
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post #6 of 25
6/22/09 at 4:33pm
Thread Starter 
Quote:
Originally Posted by Johnsteph10 View Post

Do you have a pic?

I can take one, but what exactly do you want to see?
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post #7 of 25
6/22/09 at 4:41pm
The theater area, the ceiling and the location of the beam relative to the overall theater space.
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post #8 of 25
6/22/09 at 5:57pm
Thread Starter 
Here are the pictures:







I plan to put an acoustically transparent wall at the front of the theater, so the front pole will not be visible.
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post #9 of 25
6/23/09 at 11:14am
Just use any of a number of framing methods to get the clip attachment point down where you want it. Something as simple as attaching a length of 2x4 from the joists will work.

Then all clips will be at same height, and under the beam.
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post #10 of 25
6/23/09 at 3:35pm
Thread Starter 
Quote:
Originally Posted by Ted White View Post

Just use any of a number of framing methods to get the clip attachment point down where you want it. Something as simple as attaching a length of 2x4 from the joists will work.

Then all clips will be at same height, and under the beam.

Ted, thanks for the reply. I just wasn't sure if there was some way to isolate the added portion from the floor joists for extra sound isolation.

I'm still not 100% set on this, but I can either have the entire ceiling at like 8', or have parts of the majority of the ceiling above 8' and several soffits that are at least 4" below 8' (unless there some trick to making a really shallow soffit that still uses isolation clips & hat channel). Frankly, I'm not seeing much advantage in the latter.
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post #11 of 25
6/23/09 at 6:39pm
If there's symetry with the soffits, that's a good thing.
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post #12 of 25
6/23/09 at 7:07pm
Thread Starter 
Quote:
Originally Posted by Ted White View Post

If there's symetry with the soffits, that's a good thing.

Are you speaking from an aesthetic perspective, room acoustics perspective, or sound isolation perspective?
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post #13 of 25
6/24/09 at 6:00am
a and b...

Aesthetics and room acoustics
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post #14 of 25
6/24/09 at 1:57pm
stereo dude, i'm not sure why you think you must attach drywall to that beam.

I do recommend not touching the beam as sound loves to travel through metal (then into your joists, etc)

You can work a coffered ceiling into the design and not have drywall touching the beam in any way (you can used the drop down 2x4s from the joists, go along the beam, then iso clips/hat on the drop down portion....so the drywall is maybe 1/2 inch from the beam, but not touching.....the beam dictates the design of the ceiling. That way the coffered "beams are still at 8' just like if you had flat drywalled the whole thing, but the coffered parts are much higher, and it will be rich, aestheicall pleasing, and that beam will not be touching any drywall....
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post #15 of 25
6/24/09 at 4:15pm
Thread Starter 
Quote:
Originally Posted by longtimelurker View Post

stereo dude, i'm not sure why you think you must attach drywall to that beam.

Where did I say that? I wasn't planning on attaching anything to the beam. I had fully intended to have the drywall mounted just away from beam.
Quote:


I do recommend not touching the beam as sound loves to travel through metal (then into your joists, etc)

I'm well aware of that.
Quote:


You can work a coffered ceiling into the design and not have drywall touching the beam in any way (you can used the drop down 2x4s from the joists, go along the beam, then iso clips/hat on the drop down portion....so the drywall is maybe 1/2 inch from the beam, but not touching.....the beam dictates the design of the ceiling. That way the coffered "beams are still at 8' just like if you had flat drywalled the whole thing, but the coffered parts are much higher, and it will be rich, aesthetically pleasing, and that beam will not be touching any drywall....

That would make the coffers a lot wider than I was thinking of, but that could work.
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post #16 of 25
6/24/09 at 5:10pm
right here you said it....that it will be at least 4" below due to hat channel, clips, etc....

if you dont plan on attaching anything to the beam, why does anything need to be 4" below it, as opposed to 1 inch (1/2" air space, 5/8 drywall)....

Quote:
Originally Posted by Stereodude View Post

Ted, thanks for the reply. I just wasn't sure if there was some way to isolate the added portion from the floor joists for extra sound isolation.

I'm still not 100% set on this, but I can either have the entire ceiling at like 8', or have parts of the majority of the ceiling above 8' and several soffits that are at least 4" below 8' (unless there some trick to making a really shallow soffit that still uses isolation clips & hat channel). Frankly, I'm not seeing much advantage in the latter.
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post #17 of 25
6/24/09 at 6:40pm
Quote:
Originally Posted by Stereodude View Post

Here are the pictures:







I plan to put an acoustically transparent wall at the front of the theater, so the front pole will not be visible.

I would either drop your ceiling down to 8' or mimic that soffit that you'll create for the ibeam on the other side to make it look like it was intended. I did that with my last theater and it worked out great. This theater I dropped my ceilings below the ibeam so that nothing touched the floor above at all, but I also had a 10' pour.

Are there any other spaces in the basement where you could do the theater without that one column being in the the room?
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post #18 of 25
6/24/09 at 8:18pm
Thread Starter 
Quote:
Originally Posted by longtimelurker View Post

right here you said it....that it will be at least 4" below due to hat channel, clips, etc....

if you dont plan on attaching anything to the beam, why does anything need to be 4" below it, as opposed to 1 inch (1/2" air space, 5/8 drywall)....

Uh... If you box around the beam with wood and then attach the clips and hat channel you would lose about a total of 4" under the beam even though it's not attached to the beam.
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post #19 of 25
6/24/09 at 8:19pm
Thread Starter 
Quote:
Originally Posted by shawnwalters View Post

Are there any other spaces in the basement where you could do the theater without that one column being in the the room?

No, unfortunately there isn't.
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post #20 of 25
6/25/09 at 7:49am
Thread Starter 
Here's a snapshot of the whole basement.



As you can see there are several beams and a variety of poles.
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post #21 of 25
6/25/09 at 9:10am
Quote:
Originally Posted by shawnwalters View Post

I would either drop your ceiling down to 8' or mimic that soffit that you'll create for the ibeam on the other side to make it look like it was intended. I did that with my last theater and it worked out great.

I was thinking of this idea. And using steal studs, would allow him to build a much smaller soffit then using wood.
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post #22 of 25
6/25/09 at 3:09pm
but you wont. i'm sorry you dont understand. ted told you how above, drop 2x4s from the joists, set those including hat/clips to the ceiling height you want.

you dont need to do anything, near, around, to, over, under, leftside or rightside of the beam. the drywall can span the beam, not touching it by 1/2".

good luck.



Quote:
Originally Posted by Stereodude View Post

Uh... If you box around the beam with wood and then attach the clips and hat channel you would lose about a total of 4" under the beam even though it's not attached to the beam.
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post #23 of 25
6/25/09 at 3:48pm
Thread Starter 
Quote:
Originally Posted by longtimelurker View Post

but you wont. i'm sorry you dont understand. ted told you how above, drop 2x4s from the joists, set those including hat/clips to the ceiling height you want.

you dont need to do anything, near, around, to, over, under, leftside or rightside of the beam. the drywall can span the beam, not touching it by 1/2".

good luck.

I understand completely. You apparently just don't understand what I'm posting.

You keep trying to tell me what I said, and what I know. I never said that I was going to attach something to the beam. You claimed that I was, and then cited my statement about needing 4" below the beam as proof that I said I was going to mount to it. I replied to you pointing out that if you were to box around the beam first you would end up about 4" below the beam without attaching to it. I never said I was still going planning to box around the beam or that I didn't understand.

I clearly understand that the drywall can span the beam as that is how I would get an 8' ceiling in the room.
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post #24 of 25
6/25/09 at 5:17pm
whatever smarty. you win.

read your own thread.
Quote:
Originally Posted by Stereodude View Post

I understand completely. You apparently just don't understand what I'm posting.

You keep trying to tell me what I said, and what I know. I never said that I was going to attach something to the beam. You claimed that I was, and then cited my statement about needing 4" below the beam as proof that I said I was going to mount to it. I replied to you pointing out that if you were to box around the beam first you would end up about 4" below the beam without attaching to it. I never said I was still going planning to box around the beam or that I didn't understand.

I clearly understand that the drywall can span the beam as that is how I would get an 8' ceiling in the room.
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post #25 of 25
6/25/09 at 6:24pm
Quote:
Originally Posted by gjvrieze View Post

I was thinking of this idea. And using steal studs, would allow him to build a much smaller soffit then using wood.

..and how is that...? I'm curious how a 2x4 steel stud somehow allows you to build smaller than a 2x4 piece of lumber.

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