This is my first post here, so please bear with me if I'm not quite up to speed on technical know-how or on this forum's etiquette. I'm still learning.
I have lived in my townhouse for close to two years. We are the 3rd owners, and it was built in 2001.
My main concern is sound transmission through the common walls with the neighbors on each side. A secondary concern is whether the common walls are built to code for their fire rating.
Footfall on the floors and stairs, closet doors closing, baby crying, and chairs being slid over hardwood floor are all clearly audible. When one neighbor closes her front door, I can feel a thud move through the structure, and the common wall creaks. None of this seemed right to me, especially since when we bought the place I assumed each unit was separate and independent, with it's own "exterior" walls between adjacent homes.
I was very disappointed when I discovered that my townhouse shared a single common wall with the neighbors on each side. Prior to that, I had always thought of townhomes as independent structures. Needless to say, the IRC code exception under 3.17.2 for a 2-hour fire-resistance wall instead of two independent structures is NOT my friend.
So now I'm trying to figure out if the walls I have are actually approved 2-hour rated assemblies. From the walls in the unpainted attic, I know that the outermost sheet of drywall is 1/2" (not sure if it's "X type" fire rated). The wall with one neighbor has 3 electrical penetrations; the other common wall has no penetrations. The penetrations do not appear to have any fire stop behind them (no putty pad or other visible stop), and I can clearly see the drywall sheet on the other side while looking through the gap next to the electrical box with the plates removed. The cavity is not insulated, at least near the electrical penetrations.
I have tried to measure the inside of the wall cavity by sliding a thin ruler between the electrical box and the sheetrock, and the measurement I get to the outside of the drywall is 4-1/2". That leads me to conclude that I have two sheets of 1/2" drywall on my side, plus a standard 3-1/2" depth from the stud.
So, assuming I've measured correctly, and that the drywall on my neighbor's side of the wall is the same is mine, does anyone know of a 2-hour rated assembly that uses two sheets of 1/2" drywall (either X type or non) and an uninsulated cavity? This seems to be closer to a 1-hour rated assembly, which from my reading of 3.17.2 exception, may not be to code.
Any and all help is appreciated. And again, my ultimate concern is to address the sound transmission issues, which are certainly related to the thickness of the common wall, lack of insulation, and unprotected penetrations. I have been told that my area did not have any sound transmission code in place when my townhouse was built, so the fire resistance rating of the wall assembly may be my only protection under code. I also hope it doesn't matter that our townhouse is equipped with a sprinkler system - I didn't see that mentioned under the townhouse section of the IRC.