Jim Ittenbach's Adventures in Soundproofing
It seems like it will never end, but it will one day. It's been a lot of work
and my guess is I have finished between 5-10% of the project. There are about 25 sheets or
sheetrock between the joists now. I have decided to go all the way and build a room within a
room. This requires new walls and ceiling that do not touch any of the existing structure.
This adds some new design complexities, but it also removes some of the concerns over how much sheetrock is
between the joists because the sheetrock that will make up the actual ceiling will not be attached to the
original joists. The ceiling sheetrock will be attached to the new room within a room joists, so the
deadweight rating of the original joists will not be affected by the sheetrock attached to the new,
decoupled joists. My studies at recording.org and johnlslayers.com have let me know
that I do not need to decouple from the basement floor because the mass of the floor is difficult for
sound to move. I am opting to simply purchase some iso sill padding for under the
base of the new walls to provide a minimal effort decoupling strategy for between the floor and the new
The things I have to pay immediate attention to now are the existing
duct and the structure for the walls and ceiling. I have taken down the carpet and demo'd the wall that
was near the HVAC units. This was necessary for several reasons. First if I put sheet rock on those walls I
would not be able to change the filter in my HVAC unit and second those walls would have provided a perfect
vehicle for flanking into the rest of the house structure.
My son (a sheet metal journeyman) is going to come down with his
friend (an HVAC expert) and assess what I will need to order to replace the existing duct work. Right not the
duct vibration is causing the loudest path for sound to travel. The upstairs HVAC feeds act like little
speakers. Since I have a wide open space now, pulling down the existing duct and replacing it should be
relatively easy. I think I will replace the main feed with fiberboard duct and use flex
duct to tangent off and feed the upstairs. I am going to run separate duct to the studio later. I
don't want to tap off the existing duct because I want the feeds to the studio as far removed from the
upstairs feeds as possible. Those feeds will likely be fiberboard and flex duct as well ad will tap into the
system closer to the HVAC system.
As far as the wall/ceiling structure goes, there will need to
be five beams run perpendicular to the existing joists. These beams will provide a
way to box in the HVAC duct, the I Beam and another to make sure that the new joist
lengths stay short so I can use 2X6 lumber for the joists. The beams will be 2X8 though. I am
going to intentionally create a slight pitch in the joists, between the beams so there are a few angles in
the ceiling. This will eliminate parallel surfaces between the floor and the ceiling (helping to eliminate standing
The beams will be supported by the new walls. Every place the
beams go there will be three 2X4 studs next to each other in the wall. The middle stud will be
shorter than the other two and will house the end of a beam, with the other two 2X4s making sure the beam will
remain securely in place.
This week's goal will be to remove the
pegboard from the back wall and start building some of the wall frames.
My son Aaron and his buddy Mike Menard came over to look at the
duct work I have in place. The first phase of dealing with HVAC issues is to take down the existing duct and
replace the main feed with sheet metal duct with 1" fiberglass inside. Mike will actually do a custom build of the
duct work. The feeder ducts leading upstairs will be replaced with flexduct. Once the walls are up we will design
the feeds and returns for the studio, which will tap into the system closer to the main HVAC unit so sound will
have a harder time finding its way to the rest of the house.