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Soundproofing Compromise

post #1 of 9
2/19/10 at 7:08am
Thread Starter 
Due primarily budget reasons, here is an alternate soundproofing option that my drywall contractor has recommended for the ceiling of my basement home theater:

1) Install 1 layer of drywall to underside of joists and insulate above with R19 pink batt
2) Install hat channel on this first layer (no RSIC's)
3) Install 2nd layer of drywall by attaching to hat channel

So I know this is a compromise with no green clue and isolation clips, but I'm wondering if this method will offer me some degree of soundproofing or whether this is creating the dreaded triple leaf effect?

Thanks!
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post #2 of 9
2/19/10 at 7:13am
Dreaded Triple Leaf indeed. Your improvements would be close to zero and may make some frequencies worse. Consider the use of the less expensive one-piece clips or attach the aforementioned metal channel to the underside of the joists at 24" spacing. Then attach double drywall to the channel.

This isn't decoupled, but is better than attaching drywall to the joists directly.

Keep in mind that a 15 x 30 room would only need 60 clips to go with the channel you're already describing.
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post #3 of 9
2/19/10 at 7:42am
Or you can run joists that hang below your current ones and do double drywall on those. you may end up cheaper just using clips and the channel though.
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post #4 of 9
2/19/10 at 9:59am
If you are popping for two layers of drywall then use some Green Glue. It is the best value for the dollars spent. and will provide the best results.
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post #5 of 9
2/19/10 at 11:15am
Thread Starter 
Quote:
Originally Posted by Ted White View Post

Dreaded Triple Leaf indeed. Your improvements would be close to zero and may make some frequencies worse. Consider the use of the less expensive one-piece clips or attach the aforementioned metal channel to the underside of the joists at 24" spacing. Then attach double drywall to the channel.

This isn't decoupled, but is better than attaching drywall to the joists directly.

Keep in mind that a 15 x 30 room would only need 60 clips to go with the channel you're already describing.

Thanks for confirming my suspicion on the Triple Leaf, Ted. Is your suggestion of attaching double drywall to the channel better than the "conventional" way of attaching drywall directly to joists and using Roxul Safe & Sound for insulation?

Quote:
Originally Posted by GPowers View Post

If you are popping for two layers of drywall then use some Green Glue. It is the best value for the dollars spent. and will provide the best results.

I think the reason why my drywall contractor is quoting a much higher price for dd+gg+clips+channels is that I have an old house (circa 1930's) and the joists in the basement are not level, so there'd be a big labor component to get the green glue and the drywall ceiling level. If it was just the material cost for the green glue, then I think I'd be able to do it from a budget perspective.
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post #6 of 9
2/19/10 at 11:19am
Quote:
Originally Posted by lpw View Post

Thanks for confirming my suspicion on the Triple Leaf, Ted. Is your suggestion of attaching double drywall to the channel better than the "conventional" way of attaching drywall directly to joists and using Roxul Safe & Sound for insulation?

Yes. Also, forget brand names of insulation. Get the cheapest you can fing from the local Big Box store. R19.

I think the reason why my drywall contractor is quoting a much higher price for dd+gg+clips+channels is that I have an old house (circa 1930's) and the joists in the basement are not level, so there'd be a big labor component to get the green glue and the drywall ceiling level. If it was just the material cost for the green glue, then I think I'd be able to do it from a budget perspective.

Might also be that he has an insufficient understanding of the process and has increased pricing to cover his rear. You're essentially installing 1 clip for every 5 square feet to this actually provides the easiest means to level a ceiling.
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post #7 of 9
2/19/10 at 8:44pm
The uneven joists are easily addressed by using inset 2x4s as blocking, screwed into the side of each joist. Find your lowest point, inset the blocking 2x4 up into the space approx 1/2" and level on that joist--then level each joist using the same 2x4 approach so that each blocked 2x4 is level with the others. You can then attach whisper clips to the 2x4s (run your hat channel parallel with joist/blocking). Then attach drywall to hat channel. This is how I did it and I saved some ceiling height and got the ceiling level.

Ted has drawings of inset blocking--your contractor should be able to get all the blocking level.
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post #8 of 9
2/22/10 at 8:43am
Thread Starter 
Quote:
Originally Posted by Ted White View Post

Dreaded Triple Leaf indeed. Your improvements would be close to zero and may make some frequencies worse. Consider the use of the less expensive one-piece clips or attach the aforementioned metal channel to the underside of the joists at 24" spacing. Then attach double drywall to the channel.

My contractor was suggesting 16" spacing for the channels...is the reason for 24" spacing instead of 16" because the larger spacing allows for the drywall to flex a bit? Will the larger of the 24" spacing lead to dips and bowing of the ceiling over time?

Quote:
Originally Posted by Dixon View Post

The uneven joists are easily addressed by using inset 2x4s as blocking, screwed into the side of each joist. Find your lowest point, inset the blocking 2x4 up into the space approx 1/2" and level on that joist--then level each joist using the same 2x4 approach so that each blocked 2x4 is level with the others. You can then attach whisper clips to the 2x4s (run your hat channel parallel with joist/blocking). Then attach drywall to hat channel. This is how I did it and I saved some ceiling height and got the ceiling level.

Ted has drawings of inset blocking--your contractor should be able to get all the blocking level.

Quote:
Originally Posted by Ted White View Post

Might also be that he has an insufficient understanding of the process and has increased pricing to cover his rear. You're essentially installing 1 clip for every 5 square feet to this actually provides the easiest means to level a ceiling.

I wish I had the DIY skills to do this, but I have to rely on a contractor and he's telling me that by using clips on uneven joists, he'd have to insert shims at every joist in order to get an even ceiling. By installing just the hat channels without the clips, he will not have to spend the extra time/labor for this. I think there is an element of unfamiliarity for him working with these newer techniques, but if I can get some degree of soundproofing by using dd and hat channels and perhaps geen glue, then I'll still be happy!

Thanks!
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post #9 of 9
2/22/10 at 8:50am
We need to keep in mind that your contractor has not done this work before. That doesn't at all mean anything negative. It's just that this is new for him.

Quote:
Originally Posted by lpw View Post

My contractor was suggesting 16" spacing for the channels...is the reason for 24" spacing instead of 16" because the larger spacing allows for the drywall to flex a bit? Will the larger of the 24" spacing lead to dips and bowing of the ceiling over time?

24" is what the system is tested and rated for. We get additional flex, as you stated. Double 5/8" drywall won't bow with a 24" span, as many large buildings have commercial truss systems at 24" very commonly.

I wish I had the DIY skills to do this, but I have to rely on a contractor and he's telling me that by using clips on uneven joists, he'd have to insert shims at every joist in order to get an even ceiling. By installing just the hat channels without the clips, he will not have to spend the extra time/labor for this.

If you're going to this effort, you need that ceiling decoupled. If you install metal channel on uneven joists (not decoupling), the channel will simply conform and you'll exactly replicate the un-even surface you have now. I cannot understand his perspective on this.

For a level ceiling using only channel, he would absolutely have to shim. This would involve shimming as the channel crosses each joist, which are 16" apart. That's a great deal of shimming.

With clips, there would be perhaps 20% of the shimming required.
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