|Plasterboard Resilient Bars|
The partition walls in most family
homes are constructed of plasterboard firmly attached to both sides of a wood stud frame.
When sound waves hit one side of the wall it causes the plasterboard on that side to
vibrate. Since the plasterboard is rigidly connected to the
stud frame, the vibration is transmitted right through the studwork to
the plasterboard on the other side. Those same vibrations
travelling through the studwork can also send noise throughout
adjacent floors and ceilings. Noises will radiate through the
structure because there's almost nothing there to cushion and
absorb the sound waves.
In order to dampen the sound waves, resilient 'furring' channels can be inserted between one of the plasterboard walls and the studwork. The resilient channel acts as a shock absorber, greatly reducing vibrations coming from either side of the wall.
Resilient channels typically add 3 to 5 Sound Transmission Class (STC) points to an otherwise identical wall or ceiling. This can often be enough to meet the STC ratings required.
It is important to distinguish acoustically effective resilient channels from hat channels, z-channels, and other lightweight metal furring systems. These other systems may resemble resilient channels, but they afford no movement and are simply too rigid to be effective. Only true resilient channels have any acoustical benefit.
It is extremely important to install Resilient Bars correctly. Improper installation will nullify any advantage gained from using it in the first place.
There are a few simple procedures that need to be followed when using resilient channels. On walls, the channel should be mounted perpendicular to the framing with the narrow flange along the bottom. This allows the plasterboard's weight to draw itself away from the framing. For ceilings, the flanges should all be pointing in one direction. This keeps the channels from fighting each other.
When fastening the plasterboard, the screws must be connected to the channels in-between the studs or joists. It is absolutely critical not to "short out" the resilient channels by screwing into the wood studs behind them. This rigid connection would destroy the benefit of the resilient channels.
The resilient channels should be held back from intersecting surfaces about 25mm on the side edges, and about 50mm to 75mm at the top and bottom of the wall. It does little good to carefully attach the channels in the middle of the wall when the baseboard screws connect the entire bottom edge to the sill plates. Similarly, it is easy to short out the resilient channels at the top of the wall by screwing into headers. The plasterboard attached to the channels also needs to be held back about 6mm from similar intersecting surfaces. If the plasterboard panels are jammed against the edges, then they will be rendered ineffective. The gaps should then be sealed, as air-tight as physically possible, with flexible non-hardening mastic.
When resilient channels are properly installed, it should be possible to slightly flex the wall or ceiling surface. A lack of flex indicates that the channels are shorted out by screws fastened into the wood framing. Also, it usually does not matter which side of the wall is resiliently hung.
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