Using Resilient Channels

Hey there. I am using RC for my basement ceiling to reduce sound transmission between floors. I am wondering the best way for dealing with installing electrical junction boxes in the ceiling and accounting for the added space from the RC. Do you need to add blocking to set the boxes lower than the joists?

Hi Tim,
Sure a surface mounted box would give the best sound proofing results, but rarely works on a basement ceiling because of height limitations. Actually the most important offender for sound transmission through space separators, like a ceiling/floor section, are air paths that carry sound directly past all sound dampening efforts. These are called “flanking paths”. For electrical boxes, these can be stopped by using air tight electrical boxes, usually available in large renovation centres, or on Amazon.

https://joneakes.com/jons-fixit-database/1914-Soundproofing-party-walls
https://joneakes.com/jons-fixit-database/1428-What-is-an-air-tight-electrical-box

Jon

Hi Jon,

I'm adding a rental suite to my basement and am hoping you can provide some guidance please.

I'll be installing 2 layers of sound insulation, resilient channel, and a single sheet of 5/8 drywall to the entire ceiling including the ductwork boxes, as well as on a shared interior wall.

I'm wondering how to finish the edges on the ceiling,ductwork, and shared partitions which all have resilient channel and will have both inside and outside corners?

I'm also wondering how to finish the edges where the ceiling meets the exterior wall which will not have resilient channel?

Typically I would use steel corner beads on the outside edge and paper on the inside, but I wont have backing to screw the corner beads into, and am not sure if the mud will crack given the flex of the resilient channel.

Also, from reading online some people say leave 1/4" gap and install acoustic caulk, and others say but it tight if it's only 1 sheet. Do you have a preference?

Any help would be greatly appreciated.

Thanks,
Mark

Hi Mark,

Nothing is perfect in soundproofing and the same is true with the edges of soundproofing. What you need to accomplish is an air tight flexible joint between the drywall and other surfaces. Acoustical sealant is not good because it will flow with time, it never sets. Acoustical sealant is made for putting over a stud and then attaching drywall to give it a soft landing -- but the adhesive is sandwiched in.

For an open corner joint you could use silicone caulking. Some use plastic or rubber sheets strips sealed and mechanically attached to both sides of the joint with flex in the middle. That goes for both inside and outside corners.

To hide that ugly joint you attach trim board or ogee to one side only and let it stand a fraction free of the other side. There will be a "decorative" dark line, but the seal is underneath.

None of that is easy but it makes for great sound proofing. Air seal with flexible materials and float decorative trim over the seal.

I hope that helps,

Jon

Hi Jon,
I am using resilient channel on a ceiling for sound and fire proofing. It will be from wall to wall and the interior walls build after. My question is how to attach the interior walls to the ceiling with the channels. I could not find any information on this.

Hello Marc,
If you were only working on a sound barrier, the trick is to use permanently flexible sealants, like silicone or polyurethane to seal the ceiling to the outer walls, and then again to seal the inserted walls to the floating ceiling. If you need some mechanical attachment at the top, put blocking behind but not in contact with the floating ceiling and then drive long screws upward from the new wall to the blocking. That leaves very little contact with the floating ceiling panel, hence little sound transmition.

But you say sound AND fire proofing. That is more complicated because these flexible caulking products are not fireproof. There exist fireproof gasket like materials designed to expand in a fire and close off the space around plumbing pipes, electrical wires or other passageways through a fire wall, some even collapse and close the pipes, very destructive but good fire blocking. Judicious use of these materials could do the trick, but you do need to check local code about what is acceptable to maintain a true "fire wall". I suspect that the fire requirements will compromise the soundproofing to some extent -- unless you can get all the fireproofing you need before putting up the soundproofing ceiling.

used metal channel 25 years ago in 100 apt units channels are rubbing against nails causing sqeeks this is in cielings how to solve

Hello Jack,

I have never heard of this so I am hoping someone else looking at Resilient Channels may have some experience with this. When does it squeak – when people walk upstairs? Are you sure it is the channels making the noise and not the floor boards?

If in fact the screws from the drywall into the channels are causing the problem you could simply add more screws.

If the screws going up into the wood are making the noise that could be another problem but I can’t imagine those screws coming loose unless you had used very long screws into wet lumber. See the explanation of nail-popping in the video list on the left -- Repairs - Nail-Pops.

The only way I can think of cinching up those screws without removing the ceiling would be to do observe the screw heads or use a metal detector set to very shallow to locate the resilient bar face against the drywall, then test to find which side of that is where the mounting face of the bar is located. Then either drill clearance holes in the drywall, or simply drive drywall screws right through the drywall and sink the head all the way up to squeeze the bar tight against the joist above. You may need a small exploration hole to orient you and find the joists. You have to decide if patching all those holes is better or worse than pulling the drywall down.

Anyone out there have any experience with this squeaking on a ceiling?

jon

Jon,
We are restoring the historic Snyder Mercantile building in Tenakee Springs, Alaska. The owner's residence is upstairs so we have resilent channels crossing the joists, 5/8" drywall then goes on then 5/8" of old growth recycled fir t&g. My question is about fastening the t&g. We don't want to screw it to the joists which would defeat the resilient channel concept I reckon. Can we just glue it with construction adhesive and throw a finish nail through the tongue into the channel to hold it until the glue sets up?

Really appreciate your opinion on this.
Thanks , Gordon

Hello Gordon,
Yes you can glue the t&g to drywall. If you want to avoid the finish nail -- use Quick Grab adhesive. No nails needed.
-- Jon