continued from “Master Bedroom Redo”

After scouring the internet and reading the Fine Homebuilding article several times, I came up with a list of things I could do to soundproof our bedroom/bathroom wall. Here’s what I did:

I removed all the metal hanger straps that supported any pipe and replaced them with plastic hanger straps.
metal hanger strap plastic hanger strap
metal vs. plastic hanger straps

The plumbing drain stack was originally strapped tightly to the studs in the wall from the basement all the way through to the attic. Unfortunately, changes in water temperature and the weight of the water, caused the PVC pipe to expand, move and rub against wood studs, resulting in creaking sounds. The plastic straps are more flexible than the metal straps, so hopefully it would give more with the PVC plumbing.

I also suspended the pipes between the studs of the wet wall. Fortunately we have 2 walls (or a wet wall) which the pipes run between, so every other strap was attached to alternating wall studs. This way, the PVC would not directly touch the wood. A little complicated I know, but hopefully this arrangement will pay off.

Next, I wrapped pipe insulation, but only around the PVC drain stack and not on the copper water supply. I’ve found that the copper pipes were not the cause of the noise issue.

silencing the DWV pipe
In the picture above, the MLV is the black stuff at the bottom of the picture. Insulation is the yellow fiberglass sheathed in white paper backing. There are gray hanger straps seen at the top of the picture. (And since I had this wall open, I “prewired” electrical wire for future sconces - see, I really can sneak electrical work into any project).

Mass loaded vinyl (MLV), an acoustical sound deadener, was then wrapped over the pipe insulation. MLV weighs about 1 lb per square foot, as dense and heavy as lead. The MLV was secured with cable ties to the pipe. Also, any seams were taped over with seam tape, which is essentially like a wider roll of electrical tape.

wrapping pipes with MLV
I’m almost finished wrapping MLV around the pipes.

Once the pipes were taken care of, I then filled any large gap in the structure or framing with expandable foam (or what I call “foam in a can“). This way, noises coming from elsewhere will be muffled. Although I wrapped the pipe with insulation and MLV in this wall, the plumbing stack continues below to the first floor where I am unable to open up the wall and perform this “invasive surgery”. There could be lingering sound issues coming from below.

We did do two test sessions where we alternately ran hot and cold water to make sure the soundproofing worked.

using expandable foam
Foam filling the gap.

Next, sound board (or fiberboard) was installed. Fiberboard is now most commonly used as roofing material. It is very fibrous and sold in 4′x8′ sheets. Knight-Celotex makes a fiberboard product marketed as “SoundStop” which is what I used. Unfortunately for me, I had to cut up the sound board into smaller pieces to get it behind the studs (usually in new construction, sound board is installed over the studs and before drywall). I caulked all the seams with a very elastic caulk, called Big Stretch. I could have used acoustical caulk, but I’ve read this works just as well (and is probably cheaper).

sound board
Sound board or fiber board.

The caulk was also used where the sound board meets the bottom plate and to seal up the electrical boxes.

Then came the final layer of insulation. We used the typical pink fiberglass insulation with paper backing that goes in the wall cavity between studs.

wall insulation

So that’s the soundproofing project. I’m crossing my fingers that this works, or else I’ll just have to cry. Now, I need to close up the wall.