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Context: Old rowhouse with joists running across the structure. Bathroom is on 2nd floor over the kitchen/dining room. Bathroom floor is 4" of concrete + tile.

Over the summer, we discovered a leak in our bathroom and had to have about 40 sf of ceiling removed from the kitchen/dining room area due to water damage and to provide access. That ceiling was about 1 1/8" thick, made of plaster+lath and drywall laminated overtop.

The leak happened to be located within the concrete floor, so a portion of the bathroom floor was also demoed to gain access. When the leak was fixed, the concrete was re-poured and is awaiting new tile. During the repair process, more defects were discovered and as a result, most of the cast iron in my bathroom is now replaced with ABS.

So now, without a ceiling (we've been letting everything dry out) and with ABS pipes, we have a very noisy plumbing situation: it sounds like a small waterfall when someone flushes the toilet. I'm trying to think through how I might be able to mitigate this as much as possible when I go to repair the ceiling.

The pipes run perpendicular to the joists, but only come out maybe 2' into the room.

What I was thinking of doing was creating a 'box' of rock wool: placing it under the pipes and then also placing it vertically to try and contain the sound. Kind of like firestopping, but horizontally, to block the vibrations.

I have no idea if that is going to be effective, but my thinking was that the rockwool would at least dampen a lot of the higher frequencies.

I also considered using 1/2" RC1 as a way of furring down the joists before applying 5/8" drywall. Again, not sure if this would truly help, since the ceiling would only be decoupled in about 25% of the space, essentially the area directly beneath the bathroom floor. Perhaps that's not the best solution? Would resilient channel make any difference at all if it's not across the entire ceiling?

Other option would be to laminate 2 layers of drywall - either 1/2+5/8 or 1/2+1/2 -- I need to verify if the ceiling is truly 1 1/8" all the way around. I could even put green glue in between those pieces of drywall, if that would help.

Do any of these solutions seem sensible? Or should I be thinking about it differently?

isherwood
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justpaintoverit
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  • Does this answer your question? The principles are the same. [How can I sound proof bathroom walls?](https://diy.stackexchange.com/questions/12381/how-can-i-sound-proof-bathroom-walls) – isherwood Oct 04 '22 at 19:41

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I think you're on the right track. I agree with you that the resilient channel might not be the best way here. Density could be. First make sure every pipe is well mounted at short spaced intervals so they are as secure as they can be. and then just add mass. Dense insulation with no gaps and then double drywall with all joints offset between the layers. Not seen a glue used in between the drywall layers, so I'm not sure if that would help or not.

The most important thing is integrity. Sound, like air and heat leaks like water through any gaps.

handyman
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wrap that pipe in dense sound insulation, the heavier the better

rockwool, used carpet, automotive sound deadening, whatever. due to the increased weight you may need more pipe brackets.

get the noise under control and then worry about the ceiling height. it may be that you can get enough noise reduction that you don't need to re-engineer the ceiling.

Jasen
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