Sound-proofing Existing walls (1 Viewer)

[Greg Foan]

Hello,

The walls in my soon-to-be basement HT are already drywalled. Since I don't want to rip them out, I was wondering if anyone had an idea on what I can do to increase sound isolation. I'd prefer not to lose 3 1/2" required with the "room within a room" thing per wall....but would really like to minimize as much sound as possible.

Thanks,

Greg

 

[Dennis Erskine]

Your choices are very limited given your parameters. The wall and ceiling cavities need to be insulated and/or isolated to reduce sound transmission. [BTW, you won't get a "sound proof" room in any case without tremendous expense and effort.]

At this point, you could investigate an expanding *open cell* foam product ... or other insulation product designed for retro installations. An additional layer of drywall will help as well; but, unless you're willing to do something to the cavities in the walls, I wouldn't bother with that either.

 

[Lee L]

Look up your local commercial drywall supplier. Ask them for resilient channel similar to the Unimast URC channel shown here. You attach this thin piece of metal to the wall horizontally and then attach new drywall on top of it using screws. This will give you some isolation and gives you the extra mass of the second layer of sheetrock as well a place to put a thin piece of foam insulation. Of course you will still have to finish all that sheetrock but it will only take about 1 1/2" away from your room and you can also run wires back there.

 

[Dennis Erskine]

You can use RC. Don't put foam insualtion behind it unless that foam insulation is 'open cell'. The RC will not be helpful as a isolation device if you put something rigid between the two layers of dry wall. Do not put wires in the space between the two layers of drywall unless you enjoy finding rattles. If you put rigid foam sheets between the two layers of drywall you can also achieve rattles. RC, when installed properly, can provide sound isolation. In a playback environment it can have unpredicable and negative effects on bass response.

You could install firring strips, install 1.5" fiberglass insulation and then a layer of 5/8" drywall. The firring strips would need to be slightly less thick than the fiberglass insulation.