I am drywalling the ceiling of a room under a bathroom and would like to isolate the ‘plumbing’ noise to a reasonable level. After looking over archived posts and searching online, my plan is to enclose the plumbing runs with XPS foamboard or FG insulation, then install RC-2 resilient channel for attaching the 5/8″ drywall. However, I have a few issues/questions that might be answered here:
1) How do I finish the wall/ceiling intersection if the ceiling needs to remain decoupled from the wall (so that I do not create a short-circuit for the sound to pass through? I should note that the room has curved walls, so finishing is a little more difficult.
2) Should I be installing foam strips between the RC2 and drywall (I have read about this in a couple of places, but can’t seem to find any product for this locally)?
3) What is the best material for insulating the pipes/joist bays- Fiberglass batting, XPS, ??
4) I need to have one access panel in the ceiling (under the tub plumbing)- how best to incorporate this into the resilient channel design?
thanks in advance for any suggestions!
Replies
The ideal thing would be to wrap the pipes with something about the consistency of plumber's putty. Then you wouldn't need anything else.
But I don't know of a suitable material to use (other than plumber's putty or duct seal, which are both too expensive).
Isolating the ceiling won't do much good, and in fact might make things worse. You're not trying to prevent transmission from the floor above, but from the pipes. The floor isn't moving much, especially if it's tiled. Better to have the ceiling rigidly tied to he non-moving floor than to have it loose and acting as a diaphragm to transmit sound.
Also, there's no point in decoupling the ceiling from the wall -- the wall isn't moving either, and tying the ceiling to the wall will help prevent motion in the ceiling.
Net-net: Wrap whatever you can around the pipes to silence them (the more mass the better), then put up a double layer of drywall, without all the fancy resilient channels.
update on project
The plumbing is PVC and although cast iron sounds like a good idea, it seems way beyond my capabilities...plus I didn't want to tear out existing work. The finished floor above this room has two layers of plywood and slate flooring, so not hearing anything from foot traffic above. Noticing that the water noise is almost entirely at the vertical transitions (coming out of the sink, tub and toilet traps), I wrapped these areas with foam insulation and then a couple layers of window wrap that I had laying around. This helped a little, but not enough. So I continued by boxing these areas in with plywood and completely filling the interior of the boxes with foam/sprayfoam- this made a huge improvement.
Now I am ready to drywall and am contemplating how to proceed? Everything I read, except for the comments in this thread, seems to recommend decoupling the drywall from the joists using RC. But I don't want to go through the extra work if it isn't going to help. Any more thoughts?
Look up Ted White on this site and see if he has any input. I'll guess he says 2 layers of 5/8" drywall with GreenGlue sandwitched between. A bucket of GG costs about $130 I think, but would be perfect for your project.
I have seen this once, and it worked well
The plastic drain lines-3 and 4 inch-were wrapped tite with what looked alot like the old style horse hair carpet pad. Wrapped twice and tie wired snug.
Only one layer of 5/8's board was below this in the ceiling and on the sides of the chase as it made it's way to the basement.
Foam board would act too much like a sounding drum because it would have space between it and the pipe and would resonate.
Best of luck.
Pipe wrap
You can buy f/g pipe wrap of closed cell foam pipe wrap at most well stocked plumbing supply houses. Both types have special pieces made for elbows, traps. tees and such as well asspecialty tape for sealing the joints in the wrap.
An important aspect of preventing noise in the waste pipes is making sure that the pipe is tightly supported. Generally that means hangers designed for the pipe and more than youthink you need.
Do the pipes run across the bays or parallel?
One thing I've thought about for this - sand. Cheap and simple, you just have to figure out how to keep it where you want it. I was thinking you could make some chutes around the sewer pipe with something like Sono-tube, taping the seams. Then shovel in the sand. The sand not only adds mass, but it absorbs waves as well doing double duty.
Sound Attenuation Mineral Wool Insulation
The idea about pipe wrap sounds good. You might be able to work in sound attenuation mineral wool insulation into the joist bay as well as the pipe wrap. The stuff is itchy and definately wear a N-95 or better, but its reletively cheap and effective.