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Discussion Starter · #1 · (Edited)
I have an unfinished 272 sqft room in my basement that I'd like to convert into a dedicated theater room. The room above me is the kitchen. The room suffers substantial airborne and impact noise. "Dusting off" The home Theater Book and looking online about sound proofing your ceiling I saw it was suggested to glue two layers of drywall directly to the ceiling between the joists. However I have a lot of exposed nails and glue globs at the ceiling. As the title suggests my joists are I-beam shaped. I have two qustions.

1. If I left something like a 1/4" gap between the drywall and joists (due to all the glue and nails that are going to be a pain to try and clean up) would the drywall still be beneficial? I got the impression that just the extra weight is beneficial. In the attached image Option A is the drywall green glued to the ceiling. Note:The image doesn't represent the gap I'm suggesting. All in all this would create 1/2 of gap for each strip. The joists are 16" on center.

2. The nature of the I-Beam shape gives me a 5/8" over hang. I was wondering if could avoid a lot of the pain of the nails and glue mess by attaching the first layer of the drywall directly to this beam. This is option B in the attached image. This would also give me a 1 1/2" air gap between the floor and this room.

Thanks for the help.
Nathaniel
 

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When I built my 2nd theater, I too had a kitchen above with wood floors and all the footfalls and dog nails could be heard below. I painstakingly went through the process of trimming nails and glue glogbs with a dremel so I could get the drywall to be flush on the bottom of the floor. I can tell you that it had an amazing affect on eliminating 99% of the noise from above. Since it doesn't look like you have too many nails in the middle of the floor you could always trim the DW down 1/4 inch so that it just clears the nails, but still is against the ceiling. Then caulk the gaps and you should be fine. (I did not caulk all of my gaps, just the larger ones) In the end I did 2 layers with GG in-between, then a pocket of air, then R30 insulation, clips, channel and 2 more layers of DD/GG. I'm not sure if you're doing all that, but I can confirm it does work!
 

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Discussion Starter · #3 ·
Thanks for the reply! I'm glad to hear someone with such a similar situation as me had success. I'm hoping someone will confirm that option B is also a good solution :) I'm just not sure if it's safe to tap into the beam like that.

Did you have any issues with sparks when using the dremel? A dremel was my first throught, but after searching the net for how people trimmed their exposed nails no one actually suggested using one, and there were a few different threads that talked about sparks and fire issues when using other power tools to cut them. I picked up some clippers today at home Depot that will trim them, but it won't be flush. However, I think it will be pretty darn close.

As far as what I'm doing with the rest of my ceiling, honestly, I'm not sure what my plan is. I've got all these pipes and duct-work below the joist which I don't want to lose access to, but I also know that doing as you described would be the best for sound isolation. I figure with either drywall or a dropped ceiling I'm going to still add the drywall between the joists, so I might as well do that now and see how it all sounds. My ceiling is also only 88.5 high, so a dropped ceiling might not be an option without it feeling like I'm going to bump my head.

While searching this forum I ran across people talking about their i-joists not being capable of handing the load of a double drywall, which I hadn't even considered. Was your ceiling similar to mine? I'm not sure how to determine if my joists could take the weight or not. I'm just about to schedule some quotes for framing the room, so they might be able to tell me about the load limits.
 

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having also gone through the angst of weighing the benefits of installing the DDGG on the underside of my subflooring I feel your pain.
like the sneaker company sez; Just Do It
I didn't religiously fit my drywall, nor did I caulk all joints, or fill under all ductwork. I still would do it again in a heart beat. Even without isolation clips, just fiberglass filling the cavities and DDGG directly onto the floor joists due to my height restrictions, the amount of suppression of every footstep and voice was worth the extra labor and expense. I interpreted things the same as you, the mass is doing most of the work. Most home improvement stores have a pallet or shelf full of partial sheets of drywall available cheap. Or do what I did, scavenge from dumpsters at work sites you're at for a year or two.
As far as cutting off nails, I'd invest in an inexpensive handheld cutoff/grinding wheel. If you have a Harbor Freight nearby, here's a pretty reasonable one.
http://www.harborfreight.com/4-12-in-43-amp-angle-grinder-69645.html
here are the cut off wheels:
http://www.harborfreight.com/4-12-in-40-grit-metal-cut-off-wheel-10-pc-61195.html
make sure to wear good safety goggles and gloves at the least, and a full face shield, if available.
Yes, sparks will be thrown. This is considered "Hot Work" on any commercial construction site and is to be treated with respect. Clear all flammable materials from the area as best as possible, or use a shovel or piece of sheet metal to protect delicate items that can't be moved. Cover the floor with something you can sacrifice, if it's already finished, and keep a fire extinguisher handy.
With a sharp cutting wheel you shouldn't be throwing that many sparks for too long to start any wood on fire, but best to be over cautious.
 

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Thanks for the reply! I'm glad to hear someone with such a similar situation as me had success. I'm hoping someone will confirm that option B is also a good solution :) I'm just not sure if it's safe to tap into the beam like that.
Option A is the way to go. For footfall damping you really need the mass and damping (green glue) right up against the subfloor. Option b adds mass to the area, but an echo chamber above it for the feet above. By putting another layer or two with GG in between right up against the subfloor, those foot strikes get damped very quickly. The subfloor becomes part of the damped mass.

I am about to go through the same thing, I think, but I have literally hundreds of nails coming through all over the place (it's double layer already, and when they laid the subfloor over the sub-sub floor, they nailed it everywhere (not in lines) and ALL of the nails came through. Ugh. I keep trying to talk myself out of doing it since I have mostly carpet upstairs...but the ceiling is open...so it's now or never. I'm starting to think about just pressing and tapping the drywall right onto the nails instead of cutting them off. They only stick out about a half inch or less, so it wouldn't even go through one layer.
 

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Discussion Starter · #8 ·
Thanks for the replies everyone. After my second post nudging for an opinion about option B I saw the soundproofing company article about air cavity depth, so I had a feeling that was going to be shot down. At least my ceiling doesn't have the mess that billwil has to deal with :). Also, that's for the tips on hardware and safety-wear Big mouth and weasel! This thread is definitely leaving me feeling more confident.
 

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Thanks for the replies everyone. After my second post nudging for an opinion about option B I saw the soundproofing company article about air cavity depth, so I had a feeling that was going to be shot down. At least my ceiling doesn't have the mess that billwil has to deal with :). Also, that's for the tips on hardware and safety-wear Big mouth and weasel! This thread is definitely leaving me feeling more confident.
Here is a post I did tonight of starting to lop off those nails. You might find it interesting as to a much lesser extent, you're about to be in the same boat. Ceiling Nailed Post.
 

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Good ideas. One thing never to use is a Dremel tool with a cutoff disk. Not only do those disks not last very long, but they have a tendency to shatter.
 

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Discussion Starter · #11 ·
Good ideas. One thing never to use is a Dremel tool with a cutoff disk. Not only do those disks not last very long, but they have a tendency to shatter.
Good to know.

A new question related to installation.
I'm currently moving some pipes around so the wall I want to hang my screen on is clear of obstacles. I planned on going ahead and doing the drywall between a few joists, before I block them with the new pipes. However, I realized I hadn't actually read the steps for installing the drywall with GG. I assumed since it was glue that just the glue would hold it, but watching and reading directions for the GG online it looks like I still need to hold them with drywall screws. I'm worried though because the floor above me is tiled. I guess I don't know enough about the structure of a home, but can I really safely tap drywall screws to the ceiling without accidentally driving them through the floor above? I'm assuming I'm just dealing with the thickness of plywood.
 

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The rear of my theater is right under a kitchen; the front of the theater is under the family room. I used the tool BIG reference above to cut down all the nail protrusions and dried wood glue before loading the drywall pieces between the I-joists. I do hear some footfalls, but not a whoooole lot.
 

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Discussion Starter · #13 ·
the floor above me is tiled. I guess I don't know enough about the structure of a home, but can I really safely tap drywall screws to the ceiling without accidentally driving them through the floor above? I'm assuming I'm just dealing with the thickness of plywood.
I thought a little bit more about this. My floor is 3/4" thick. Drywall is 5/8" thick. Can I get away with 1" drywall screws?
 

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1" or 1 1/4" should work fine. If you use 1", I would use more as you'll barely be getting into the wood through that 5/8" Type X sheetrock. 1.25" might be better...just be careful on driving them too deep if you use the latter. Are you using Green Glue?
 

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Discussion Starter · #15 ·
1" or 1 1/4" should work fine. If you use 1", I would use more as you'll barely be getting into the wood through that 5/8" Type X sheetrock. 1.25" might be better...just be careful on driving them too deep if you use the latter. Are you using Green Glue?
I am going to be using GG. 1 1/4" makes me nervous since that only leaves me with 1/8" before I actually penetrate through the floor. While it's my understanding that GG can't be used alone to hold drywall in place I have to believe it would help elevate some of the strain the screws will be facing.
 

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Good ideas. One thing never to use is a Dremel tool with a cutoff disk. Not only do those disks not last very long, but they have a tendency to shatter.
I never had a problem with a dremel and the cutoff disks shattering, but they do wear down fast. My dremel has one of those quick connect heads so it was a breeze to swap them out. I got through 25-30 nails per disk. They do throw sparks so definitely wear goggles and a long sleeve shirt. Had at least one cutoff nail drop on my arm and cause a burn.

I am going to be using GG. 1 1/4" makes me nervous since that only leaves me with 1/8" before I actually penetrate through the floor. While it's my understanding that GG can't be used alone to hold drywall in place I have to believe it would help alleviate some of the strain the screws will be facing.
I'd go with 1" for the first layer. If you drive it properly, it will go just a bit into the drywall and should stop just short of all the way through the subfloor. I'd guess your tile was applied onto a layer of grout or tile cement, so even if you go a little through, you'll probably avoid the tile anyway. Definitely don't expect the GG to hold the pieces in place.
 

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Nope...I didn't ask about GG for holding power, I asked for the extra 1/16th of space it will likely give him. DON'T USE GG AS, WELL, GLUE. :) Also, as mentioned, your tile is not directly on your subfloor, there's likely quite a bit of space (another 1/8" at least) before hitting tile. That said, do what makes you feel comfortable, but if you go with the 1", like I said, just use a few more because some of them will likely not have as much holding power. If you go with the longer ones, be careful about pulling through the paper. Either one will be fine if you're careful, I think. Good luck, and keep us posted.
 

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Discussion Starter · #19 ·
Thanks again everyone for the info. I didn't realize GG had no adhesive properties. BTW, billwil, your Whisper Mountain Theater thread has been quite interesting to look through.
 

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Thanks again everyone for the info. I didn't realize GG had no adhesive properties. BTW, billwil, your Whisper Mountain Theater thread has been quite interesting to look through.
Well, let me clarify. Green Glue is not an adhesive at all.....unless of course you get it on something you don't want it on, or yourself, and then you'll find that it's the strongest stuff in the world. :) Just kidding, of course, but if you use it you'll know what I mean...tenacious stuff.

And I'm glad you're enjoying the build. I wish it was done and we were all enjoying reminiscing about it, but alas, here I am in the midst of another major project...so I might as well enjoy it. ;)
 
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