Okay, time for more post. Here’s part II of how to soundproof a wall.
By this point, I’ve already sealed the gaps in the other side of the wall with goop, and padded up the boxes and other protrusions. The blue-jeans cotton insulation has gone in, and it’s onto finishing the mass-loaded vinyl.
Once you’ve got the first course up, you’ve got to put up the second course above it. This is harder than it looks, since it weighs about one pound per square foot, comes in four-foot wide rolls, and you have to hold it up eight feet off the ground. I suggest you get help from your resident fourteen-year-old.
You want to make sure it covers everything and is continuous, since it acts like a barrier to block the higher frequency sound as well as medium frequency. When it comes to openings like doorways, though, you can either have it stop or wrap around the wood. You’re making the wall assembly heavier (more massive) and less able to vibrate and transmit sound, so any bit should help.
After both courses are up, held in place with the plastic-washer-style roofing cap nails, you seal it with lead tape. I’m probably going to have to add another disclosure form when I sell the house because of it, but you’re closing up gaps that allow air (and sound) through, and adding yet more mass to the wall.
Here’s also where you can fix bigger gaps, like where I misjudged the curve of each section of vinyl.
While it’s good to have continous sections, it’s not required because of the lead tape — you just need to use a bit more to seal the seams. In the living room, I cut sections of vinyl out to fit around the ceiling beams.
After the vinyl and lead tape comes the green foam padding tape. This resembles double-sided tape, because that’s pretty much what it is — foam tape that will go between the vinyl and the wallboard to provide another layer of padding (and thus sound dampening). The green tape gets placed over any studs or wood members — remember, the mass-loaded vinyl should be loose in the wall cavities.
So follow the stud (and fireblocking) pattern on one side…
and on the other.
Perfect alignment isn’t entirely necessary }:>
Next comes the soundboard. This seems to be a lightweight particle board, almost as though it were made from shredded cardboard bits. Here you have to use more of the sealant goop to seal up the gaps between the boards.
Note how the electrical boxes are still protruding from the soundboard. Here’s where those adjustable depth boxes (where you can adjust from the outside after the wallboard is put up) come in really handy.
Then, the sheetrock goes up. Both the soundboard and sheetrock are 5/8″ thickness, instead of the more normal 1/2″. Note also how the seams on the sheetrock are staggered from the seams on the soundboard.
Here’s a good shot where you can see a cross section of the whole thing, by the rack opening. The green foam tape is on the side of the frame, between the frame and the rack itself. Then you can see a tiny bit of the stud, then the mass-loaded vinyl. You can’t see the foam tape here, but you can then see the sound board, and then the drywall.
After this all goes up, tape the seams and fill the screw holes like normal (I had help from a friend on this because I’m hopeless when it comes to mud work), and you’re ready for texture and paint!
Next time — doors and the final sound level meter test!