Resilient channel for shop sound attenuation

[Victor Robinson]

I'm considering using RC behind the drywall in the garage to help with reducing sound transmission to the neighbors (attached row houses). This is in addition to Roxul batts. My understanding is that a proper RC drywall installation keeps the drywall floating and you must not hit the framing with the drywall fasteners. So for shop walls, is it essentially useless since I would expect to be able to screw things to the wall (e.g. cabinets, shelving, racks, etc). Or is it still better than not using RC?

Dont want to use green glue and double layer dw - too expensive for this project.

[Victor Robinson]

Well based on some more research it seems like RC walls are really pointless in this application and rapidly decline in sound attenuation if short-circuited.

[Bob Falk]

FWIW, I insulated with Roxul between my new kitchen/living space and my new garage shop. 6" of Roxul and a layer of 1/2 drywall in kitchen and 5/8 in garage. I did the same in my garage/shop ceiling (master BR overhead), however I used 1" of foam board (mainly for the radiant heat floor), 6" of Roxul and added a second layer of drywall between the joists. It certainly isn't what I would call soundproof when I am running my dust collector and shaper or router, but it would be intolerable without. To be honest, I haven't been on the receiving end as i am in the shop when my tools are running, but I've asked my wife about the noise and she says no worse than a lawnmower running outside (with windows closed). I considered resilient channel, but decided it was probably not worth the cost (I may be wrong). In any case, I mainly woodwork during the day when I'm not bothering anyone.

[Mel Fulks]

Since its a garage it's easy to make the wall thicker , and temporary if desired, and use Bob's method. And possibly add one more layer of Roxul Safe N Sound

[Victor Robinson]

Since its a garage it's easy to make the wall thicker , and temporary if desired, and use Bob's method. And possibly add one more layer of Roxul Safe N Sound

Yeah I think you're right, though I'd prefer not to build out the wall further (from both a labor point of view and losing valuable inches from my shop dimensions!). Already kind of bummed to lose all that storage between the studs, but then again it was just encouraging hoarding of scraps.

These are the exterior side walls of the house (2x6) and actually just have the house siding on the "exterior" side (no sheathing), with probably a few inches of air gap, then the neighbor's siding. In another (non-shop) portion of the house I used 2 inch EPS against the siding sealed with canned foam between the studs plus roxul, but for sound attenuation I don't think this approach would work in the garage as the rigid foam may actually serve to amplify sound (???). Maybe furring out and two layers of Roxul would be best without any additional air sealing...not really necessary here in our climate...just thinking aloud.

[Victor Robinson]

FWIW, I insulated with Roxul between my new kitchen/living space and my new garage shop. 6" of Roxul and a layer of 1/2 drywall in kitchen and 5/8 in garage. I did the same in my garage/shop ceiling (master BR overhead), however I used 1" of foam board (mainly for the radiant heat floor), 6" of Roxul and added a second layer of drywall between the joists. It certainly isn't what I would call soundproof when I am running my dust collector and shaper or router, but it would be intolerable without. To be honest, I haven't been on the receiving end as i am in the shop when my tools are running, but I've asked my wife about the noise and she says no worse than a lawnmower running outside (with windows closed). I considered resilient channel, but decided it was probably not worth the cost (I may be wrong). In any case, I mainly woodwork during the day when I'm not bothering anyone.

I'm curious in your ceiling insulation with the foam board and the roxul, how many air gaps do you have? I've heard that the foam board can actually amplify sound, especially in conjunction with the "triple leaf effect" (two air gaps).

[Victor Robinson]

I'm curious in your ceiling insulation with the foam board and the roxul, how many air gaps do you have? I've heard that the foam board can actually amplify sound, especially in conjunction with the "triple leaf effect" (two air gaps).

Ah nevermind - batts wouldn't create a triple leaf effect, only the "solid" parts of a wall assembly, so if there was a gap between the foam and the sheathing (or subfloor in your case), then there would be an issue, but a gap between foam and roxul and another between roxul and drywall would be okay.

http://www.greengluecompany.com/site...eaf_Effect.pdf

[Mel Fulks]

If you go the route of a temp wall ,I would cover with sheet rock. Would help stop noise and Roxul dust getting into the air.

[Bob Falk]

I just wedged the foam into the space between the joists with a tight friction fit, then put up the Roxul, then drywall. Because my ceiling had I-joists, I just cut the drywall to sit on top of the bottom flange of the I-joists and then used construction adhesive (read cheap) to glue the drywall to the flange...then the drywallers came in and put 5/8 drywall everywhere in garage/shop. I don't think I have many airgaps. Everything I read suggested that you need to use mass and, if possible, decouple the sound transmission (e.g. resilient channel). Drywall is cheap and heavy. Worked OK for me.