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Changes in Resilient Channels

Acoustical Consultants often specify resilient channels to improve the sound isolation of a construction assembly. Sound isolation is the amount of noise the wall or floor/ceiling reduces. Resilient channels are installed perpendicular to the stud or joist. This reduces the number of points were the gypsum board system is actually in direct contact with the framing system (called a lattice connection system) and provides the gypsum board some ability to "deflect" when sound waves come in contact with it. This deflection "absorbs" some the acoutical energy and therefore reduces the sound levels heard on the other side of the partition.

There are several manufacturers of resilient channels. The original manufacturer US Gypsum (USG), created and tested the first resilient channel USG RC-1, but as is often the case the copies are not a good as the original. When competitor resilient channels are tested side by side against the USG RC-1 channel, the RC-1 always outperforms the others. For example, when we were called in as an expert for a multifamily housing project and had a wall or ceiling opened up for inspection, in every problem case a non-USG RC-1 channel was used. When the USG RC-1 was installed and the ceiling was refinished, the problems almost always went away. The installation of the correct channel and even the proper installation of channels seem to be a challenge in the field at a job site. There was one project that had three different channels installed on one wall and none of them were the specified USG RC-1.

The basic design of a resilient channel is a metal channel bent into three sections: a flange about 40 cm wide (where the gypsum board is attached); a section about 12 cm tall (with long slots routed into it to provide some spring); and the third flange about 15 cm wide where the channel is attached to the joist or stud. (Go to http://www.ta-inc.com/newshtml/rc.htm for more information.) USG has sold their product to Unimast, which then sold it to Worthington Industries. Worthington Industries' Dietrich Division now manufacturers two versions of resilient channels, the RC Deluxe and the URC, yes it is confusing. The RC Deluxe is very similar to the original USG RC-1 but the URC version has smaller slots and if tested would not perform as well. So, while we still specify resilient channels we have been looking for a better solution that will be a little more contractor friendly. One new product is a metal clip with a rubber busing that will support a traditional hat channel. In looking at it, it seems to be a system that field crews will have an easier time installing. The extra thickness will help minimize some of the common problems we see where the installers use a screw that is too long and screw through the channel and into the framing system. This "short circuits" the resilient channel, eliminating the deflection component of the system. The new product tests well in the laboratory. We have specified it in some of our more recent multifamily projects and a couple of commercial projects. The projects are not finished, so we do not have actual field test results, but from what we have heard, everything is looking and sounding good.


Thorburn Associates, April 2004

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