Soundproofing a Ceiling
joenorm
| Posted in General Questions on
If I wanted to soundproof an existing ceiling what would be the technique? There are no lights or anything up there. Would I install a channel of some sort and then add a second layer of drywall? If I wanted to do wood paneling instead, would there be a method to making it soundproof?
I regretfully missed the opportunity to add sound proofing to the ceiling cavity in this particular instance.
thanks
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The best thing you can do is to decouple the ceiling, so you'd put up hat channel on clips and then hang a layer (ideally two layers) of 5/8" drywall from the hat channel. This will actually do more to soundproof the ceiling than just stuffing batts into the cavities between joists. If you want to do wood paneling, you still need the mass of the drywall, so you'd probably want to put the paneling over the drywall, being careful to screw the paneling into the hat channel. Don't rely on the drywall along for support, since drywall isn't very good at holding fasteners, especially vertically like this.
Bill
Joe norm,
If you want to use acoustical channels or clips, you need to take off the existing drywall or you will have a small cavity that makes the ceiling worse than if you had left it alone. The channels need to be attached directly to the underside of the joists.
The most predicable way to do sound attenuation is to choose a rated assembly and reproduce it entirely. Then you know what the result will be. Here is a link to a whole bunch of options from our building code: https://free.bcpublications.ca/civix/document/id/public/bcbc2018/bcbc_2018dbp9rt
In a retrofit situation your best bet is more layers of drywall. Everything else means demoing the existing ceiling and starting with an assembly Malcolm linked to earlier.
Two layers of 5/8" over the existing 1/2" does a pretty good job of keeping the sound down. I would start with one layer and see if its good enough. Since wood is light, T&G itself does nothing for sound, this can be nailed up over the drywall with long nails into the ceiling joists or strap out the ceiling and nail to that.
I have 5/8" up there attached to joists currently. Above it is Advantek subfloor and then finished floor. The cavity is empty. Sound travels through surprising well. Demo is not an option. Would another layer of 5/8" be worth a try?
It depends on what kind of sound is “traveling through”. If you hear voices, for example, another layer of 5/8” drywall will help. If the annoying sound you want to block is footsteps, then a second layer won’t do as much, and you’ll really need to decouple the ceiling (hat channel as described above) will be needed. Decoupling helps to block conducted sound that is coming through the rigid connections to the joists.
Bill
Putting up a second layer of gyp board then requires finishing and painting that second layer, as it is what is now exposed. This creates dust and makes a mess. Since you are going to create dust and make a mess anyway and thus are going to need to remove everything from that room and tape off the area from the house and the HVAC system, just go ahead and add a day to your schedule and demo the existing gyp in the room.
1. You have to prep and put up the plastic anyway
2. Demo the existing gyp and remove ALL fasteners. Makes sure you take advantage of this opportunity of exposed subfloor above to either push shims or construction adhesive into ANY tiny gap between the subfloor above and the joists. That will help some of the echo sounds. Also seal all floor penetrations you see from below.
3. Install the clips yourself to ensure they are properly installed or get a good crew to install
4. A professional crew can hang back 2 layers of gyp on a ceiling of a room in a day. However, you might consider gyp specifically made for sound attenuation. They have some that is two layers of 3/8" with either acoustical sealant or lead sandwiched between. It costs a bit more in materials, and a bit more in labor because it is heavier, but well worth it. You will be much happier with the results. The main pain point is the dust and disruption, which you would have for a second layer of gyp anyway, so just bite the bullet and do it right.
5. Then you have the bedding, taping, sanding & finishing, and subsequent priming & painting you would have anyway with a 2nd layer.
Reviving this thread........
I am thinking of ways to reduce destruction. Would adding dense packed cellulose in the cavity help? I don't see how it couldn't. If so I could just drill a hole in each stud bay. This would be a lot less messy and economical than tearing the ceiling down.
It must help with transmission, absorbing some of the sound as it travels through the framing members?
I/m not looking for perfection(Hat Channel), just improvement.
The fill between joists helps sound travelling through the air, between the two diaphrams formed by the drywall on one side and the subfloor on the other. Ideally you don't want a full fill though, you want a small air gap between one diaphram and the other, which is why the Safe'n'Sound mineral wool batts are slightly thinner than the thermal batts (3" for a 2x4 wall, for example, to leave a 1/2" air gap). If you fully fill the cavity, you can sometimes make things worse in some frequency ranges.
I do think overall blowing in some cellulose will help quiet things down for you. Just remember that it will help more with transmitted sound like voices than it will with conducted sound like footsteps. A second layer of drywall over the existing ceiling will also help, since it will make the ceiling more rigid, and will add mass. The extra mass will also help to damp down sound.
Bill
When you look at STC of tested assemblies, the type of fluffy doesn't seem to matter. Of course this is for ideal assemblies without any flanking.
With an existing house, there is a lot of flanking paths and lot of air leaks, so dense pack can makes a big difference by sealing it up. Also a full fill of fluffy tends to get you about a 6dB increase in STC which is noticeable by most people.
I haven't tried it on ceiling but dense packing walls on a busy street did make a noticeable difference in sound. Dense packing is a pretty messy process but so is drywall work.
It will definitely make the sound situation better and if not enough, you can always go back to more layers of drywall.