Re: Sound Class Transmission Rating
From: Fred-List manager (
Date: Tue, 10 Mar 2015 06:09:05 -0700 (PDT)
Stew Mayer <mayers [at]>
is the author of the message below.  It was posted by
Fred, the Cohousing-L list manager <fholson [at]>
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--------------------  FORWARDED MESSAGE FOLLOWS --------------------
Your double 2x4 stud wall assembly with woven batt insulation is a
practical, cost-effective construction, no problem there.  Here are a
couple of low-cost and simple enhancements since additional sound
baffling needed:

1. Apply a bead of caulk at the ceiling/wall intersection (if
practical at this point) and another at the floor/baseboard

2. I would not recommend simply adding additional layers of drywall or
gypsum board hard against the existing wall board, not enough sound
reduction to warrant the expense.  However, with either of the two
following additional steps you will see sound transmission reduced:

        a.      before applying new board run vertical continuous beads of
acoustical sealant (available at any building supply, comes in a
cartridge) over where studs are locate in existing wall .  Then apply
the board with drywall screws, only tightening them to the point where
the board is straight/true. Wait 24-hrs, then tighten those screws
down and finish your wall.

        b.      better idea - install metal 'acoustical channel' (a drywall
supply item readily available) vertically into each stud.  Then
install your new drywall.  These channels are relatively inexpensive,
easy to install, and very effective in "floating", or separating, the
old and new drywall installs.  You will see a significant improvement
in sound reduction.

The above presumes your sound problem is wall transmission; if the
sound is actually traveling under the walls thru the flooring between
units, that is a more complicated fix.

Good luck!

Stew Mayer

Architect, Partner, Communitas Development Associates
508.962.4721   -  Boston
760.705.4369   -  San Diego
mayers [at]

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