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Discussion Starter · #1 ·
I'm finishing the framing stages of my HT room in the basement of our house. The room will be about 15' 3" x 23' x 8'4". I'm not going to be able to frame in a false ceiling to make a complete "room within a room". However, is there anything you can do in this case to aid in minimizing sound transfer to the above floor?


I already plan on double drywall, 5/8" over 1/2" on both walls and ceiling, and stuffing the gaps between floor joists with R-30 insulation. Would doubling up on floor joists be a good idea or a waste of time?


Second, if I'm going to have 1 1/8" of drywall on the studs, then 1" of furring strips arould each electrical box on top of that for a total of 2 1/8", how do you accomodate this huge thickness when hanging electrical boxes on the studs? I was unable to find this addressed in past posts...


Thanks,

Chris
 

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1st, IMPHO, Doubling up on the floor joist above would not be a dollar wise spent. I don't exactly understand your statement: "I'm not going to be able to frame in a false ceiling to make a complete "room within a room". But, then you said you were going to:"I'm not going to be able to frame in a false ceiling to make a complete "room within a room". Please clarify.

2nd, use the retro gang boxes that have mounting holes on the face of them, we use these in our installations.

HTman / HTMMCo.
 

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For the electrical you can use the retro-fit boxes, or standard boxes with box extenders.


Doubling up on the ceiling joists would be of no benefit. You could however, double up using new joists, notching an 1" out of each end (or using joist hangers) so the new joists are offset from the existing by 1" to the side and 1" lower. Still fill the joist cavities with insulation.
 

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Discussion Starter · #4 ·
Oops.

To clarify: I wasn't going to do as Dennis said, notching new joists out to separate the theater ceiling from the floor of the room above, I didn't think. I assumed that the new joists had to be supported only by the walls of the theater room. Is it really OK and still effective just to notch them and hang them from the same plates as the original floor joists, Dennis?


Thanks,

Chris
 

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Discussion Starter · #5 ·
Can anybody who has experience in this part of the construction phase please clarify this for me? If you notch new joists out so they're not touching the floor above, do you just 'toenail' them into the plates that the original joists are on to keep them in place?


-Chris
 

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Notching structural members like this is not allowed by most building codes; however, these are not considered structural since the only weight being cared is the dry wall. So, it is ok.


For ceiling mounted projectors, the other advantage of this approach is the projector won't jiggle as people walk across the floor above.
 

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Instead of notching, just make the interior theater walls 1" to 2" shorter. Same net effect and no notches.


Ted
 

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Chris, Coming from someone that has "hands on" experience It is okay to toe nail your ceiling joists in. Just place them on top of the walls. I would suggest using a double top plate on your walls for strength. Cut your studs a 1 .5" shorter to comp. for the double top plate. Hope this helps. David
 

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If you're using standard SPF I wouldn't just toenail. They'll warp.


Actually many will twist regardless of what you do which is why I advocate the use of micromal beams or I joists.


I found great success with a specialized joist hanger, used upside down.


Consider what I said about making the theater wall height 1" to 2" below the existing joists. The new "floating joists" will simply set on top, neat as a pin.


Ted
 

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Discussion Starter · #10 ·
Unfortunately, I can't do this as I have an 8" I-beam running down the left side of my room, about 2 feet into the room. I am currently planning on hanging notched 2x10's from this beam and the plate on the opposite side of the room. The beam will then be covered with a soffit, and a matchin soffit will be constructed on the opposite wall as well. Should I really be concerned about them warping in this case? Holding only the weight of the drywall?


-Chris
 

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If the new joists contact that beam, they'll transmit the sound you're trying hard to isolate.


Ted
 

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Ted, We haven't experienced any warping on our installs, but thats not to stay it couldn't happen.

Chris, I agree with Ted on the sound transmitting thru the beam though. You might want to rethink that aspect of your room. David
 

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David,


Any warping is going to occur over time and that the drywall be hung by then.


Any standard framing that uses SPF (Spruce, Pine or Fir) requires cross bracing to keep this from occurring. We've all seen this cross bracing in older basements. It's code.


This happens with all SPF. It's not a reflection of the quality, it's just wood. Warping WILL occur in some percentage of the beams. Could be 10% or 25%, but the odds of installing a floating ceiling without any warpage is somewhat slim.


Consider microlams or "I joists". Are they overkill from a weight perspective? Certainly. They are immune to warpage, however.


Ted
 

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Ted, Cross bracing was a given here. I will also agrre that microlams are "better" but are they immune to Chris's wallet?

I'm sure like many of the DIY on the forum their budget is the largest variable.
 

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I'm sure I seem argumentative, and for that I appologize, but how do you apply cross bracing with the new joists? Unless they totally below the old joist network?


Thanks for your patience.


Ted
 

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I am working with Dennis on my HT and had not gotten around to bugging him yet with my question that this thread almost answers.


My basement's ceiling has cross bracing and that is keeping me from installing new lower joists on which to hang my floating ceiling. If I attach joist hangers to the cross bracing, then I am defeating the whole purpose of a seperate ceiling structure.


I cannot take out the cross bracing due to building codes nor can notch I out the cross bracing. Does this mean that a floating ceiling is not an option for me?


PS - Many thanks to the generous professionals and enthusiastic amateurs who take their time to help the less experienced.
 

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What's the current height from the floor to the underside of the existing joists?


Ted
 

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Ted, I don't know the source of your dialogue, if it's from a aurgmentive stand point or a educational one, but I'll take you at your word. My purpose here on the forum is to inform and educate HT enthusiast with my back round in engineering and "hands on real world building". As you know, most of the people here aren't dealing with ideal situations, and unorthodox methods are often required. " In general-" there is more than "one way" to do things. You don't have to criticizes something just because its different then your way. (Pissing contest) I have "learned" as much as I have educated here on the forums, I acquire wisdom everyday, its a foolish man who thinks he possess all knowledge.(There is only ONE who knows all! No, not you Dennis, (haha) He doesn't reside on this earth) Well, enough of that Ted, on with the show.

The ceiling joists don't have to be "totally below to apply cross bracing". With his ceiling being 8"6" he should be able to cross brace them.
 

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Chris,


This is your thread, let me see if I can help you. It appears as if you're looking for significant acoustic isolation. Personally, I would continue to look to see if you can still use a floating ceiling. All the drywall in the world on the side walls won't matter if there's significant contact with the joists above, so let's explore that option a little further.


Am I correct in assuming that your existing joists overhead are wood with cross bracing? If so, the cross bracing (wood or metal?) likely forms an "X" in between the existing joists. Could you provide the measurement from the floor to center of the "X"?


Also, could you clarify exactly what the joist structure is? Wood, "I" joists, floor truss? And how tall are they?


You described this beam. I assume that the existing joists rest atop the beam which runs down the center of the house? Is this a steel beam or wood? Do the joists rest atop a 2x6 or something, which rests atop the beam? Or do the floor joists set directly on the beam?


Ted
 
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