The partition walls in most family homes are constructed of Drywall (Sheetrock/Gypsum Board) firmly attached to both sides of a wood or metal stud frame. When sound waves hit one side of the wall it causes the drywall on that side to vibrate. Since the drywall is rigidly connected to the stud frame, the vibration is transmitted right through the studwork to the drywall on the other side. Those same vibrations traveling through the studwork can also duct noise throughout adjacent floors and ceilings. Noise will radiate easily through the structure because there’s almost nothing there to isolate or absorb the sound waves.
To reduce this effect and to dampen the sound waves, resilient metal channels can be inserted between one of the drywall walls and the studwork. The resilient channels act as shock absorbers, greatly reducing vibrations coming from either side of the wall from passing through the wall. Absorbent mat is used inside the wall to cushion the channel/drywall and to provide an absorbent compartment to trap sound waves.
The resilient channel technique by itself typically adds 3 to 5 (or more) Sound Transmission Class (STC) points to an otherwise identical wall or ceiling. This by itself, is not usually sufficient to meet total noise level reduction requirements under most circumstances. Other added construction materials and techniques are usually needed, such as adding absorbent mat and/or barrier material to the wall space. Some considerations are the amount of wall space that can be donated as mounting the wallboard on these 1/2″ thick channels increases the thickness of the wall (or ceiling) somewhat.
It is important to distinguish acoustically effective resilient channels from hat channels, Z-channels and other lightweight metal furring systems that drywall contractors are used to installing. These other systems may resemble resilient channels, but they allow no movement and are simply too rigid to be effective. Only true resilient channels have any acoustical benefits.
It is extremely important to install these channels 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 them. In existing walls, large opening should be cut in the drywall panels to Open Up the wall and expose the dead air to the new wall covering. One large dead air space that is created and linked together contributes greatly to the sound control system. In fact, adding furring strips (spacing blocks) of 1″-2″ increases the sound reduction effect (especially at low frequencies of sound) by increasing the dead airspace. The channels are then applied directly over Super Soundproofing MLV barrier mat that should be first used to cover the wall. The new drywall panels are then coated with absorbent closed cell matting material to create an absorbent compartment to dampen sound waves. The absorbent mat is applied like wallpaper using contact cement and a roller. The thickness of material used depends on the level of sound control desired: More is better! In an open, studded wall, sound barrier material (MLV) is typically stapled to the studs, but for best results, between a layer of soundboard and drywall attached to the channels, even though it can be cut and weaved between the studding. On walls and ceilings, the channel should be mounted at a right angle to the framing. On walls, mount with the narrow flange along the bottom and the larger flange up. This allows the drywall’s weight to draw itself away from the framing. Make sure all the flanges should are pointing in the same direction.
When fastening the drywall to the channels, the mounting screws are to be driven into the channels in-between the studs or joists. It is absolutely critical not to “short out” the resilient channels by screwing long screws into the studs behind them. This rigid connection would destroy their benefit of “Floating” the wall or ceiling assembly.
The resilient channels should be held back from intersecting surfaces about ¼” on the side edges, and about 4-6″ from the top and bottom of the wall.
It does little good to carefully attach the channels in the middle of the wall if one installs baseboard screws that may connect the entire bottom edge to sill plates. Similarly, it is easy to “short out” the resilient channels at the top of the wall by screwing into headers. Leave space where the wallboard is not connected. The drywall attached to the channels also needs to be held back about ¼” from similar intersecting corners. If the drywall panel edges are jammed against wall or ceiling panels, then they will tend to be rendered ineffective. For walls, the drywall edges should be resting on neoprene vibration pads and sealed with caulk before the wall is finish taped and painted. This provides a supporting base on which to mount the wall and “Unload” the channels from the weight of the drywall panels. Use 2 of the 2″ pads per vertical sheet of drywall or, 1 every 2′ or so.. The weight of the drywall will tend to crush the drywall edge down on the pad, narrowing the gap to the floor to be sealed. The gaps should then be sealed, as air-tight as physically possible, with plenty of flexible non-hardening caulk. “Backer Square” or Lead tape can also be used for this.
When the resilient channels are properly installed, it should be possible to push and slightly flex the wall or ceiling surface. A lack of flex indicates that the channels too rigid, perhaps because they are shorted out by too long of screws fastened into the wood framing. Also, it usually does not matter which side of the wall is resiliently hung. Of course, doing both sides of the wall is better. For ceilings, use RC-2, which is simply two-legged RC-1. If not readily available, RC-1 can be used but more of it is needed.
Resilient Channels and “Soundboard”
Sound deadening board is a material made from compressed wood fibers (Sometimes called “construction panel”) another similar trade name is “Homasote” ( Somewhat better, but considerably more expensive) and it functions as a thick paper cushion. “Celotex” also makes a version. It used to be that theory was that soundboard would provide basic resilient isolation for the drywall layers on top. However, screws or nails breach the system and reduce the isolation to the point where, acoustically speaking, it would be better to replace the screws with construction adhesive as much as possible. When using resilient channel and double layers, use extra care to screw the drywall mostly into the soundboard and not through to the metal channels and not to touch studs underneath. The benefit is that the different physical acoustical properties of the drywall and soundboard complement each other, improving sound reduction qualities. Mass loaded barrier is appropriately used between the soundboard and drywall for many added STC points. A construction adhesive like “Liquid Nails” may be used if need be.
(Note the large flange is up).
Resilient channel is a thin metal channel designed to substantially improve the sound insulation of drywall, sheetrock and plasterboard walls and ceilings. The channel effectively isolates the drywall from the framing studwork, reducing €˜direct contact€™ to help dissipate sound which would normally be directly transferred through the frame. This system is easy to install and produces dramatic results. The channels measure about 1/2″ in thickness and the wide flange (drywall mount) is about a 1 1/4″ wide. The vibration absorpsion properties of the channel can be additionally enhanced by applying thin (1/8″) “Super Soundproofing Absorbent Tape” to the flange of the drywall mount. If not using the channel or Sound Clips, at least use the tape on the face of the studs.
Example: A standard metal framed stud partition lined both sides with ½” drywall with fiberglass insulation in the wall cavity, (Note: “Packing” in the insulation many may think increases the thermal properties, but it will definitely decrease sound reduction), gives an STC rating of around 20-25 or less.
Conversation can be heard).
The same wall, but with just resilient channel between the drywall and frame, to one side only, can increase the rating to as high as a STC rating of 35 or so. (Now, only loud shouting can be heard).
Even greater improvements in soundproofing the wall can be gained by:
- Adding an additional layer of drywall on channel to the other side.
- Adding a layer of “Wonderboard” or “Duroc” a concrete based construction material to add more mass (this will help reduce low frequency sound). Add to existing wall, first.
- Adding a layer of “Super Soundproofing Silencer “Mass Loaded” Barrier” to the existing wall or adding a layer of Super Soundproofing absorbent Mat” to the existing wall, or both.
- Mounting “Soundboard” (Celotex-sound deadening board) or “Homasote” to the channels before the drywall is attached. Caulk and seal the edges of the panels for best results.
For maximum effect and best results: use “all of the above”.
Channel Cutting: Resilient Channel can easily be cut with tin-snips or hacksaw.
Installation: Walls require less channel than a ceiling for obvious reasons. If they are to be fitted directly to the underside of an existing ceiling, furring strips should be screwed to the ceiling at 2′ centers, right angle to the joists.
The absorbent mat of the appropriate thickness should be applied inside the joists/studding before this stage.
Care must be taken to ensure that the attachments used are secured to the underlying joists where they cross and NOT just to the existing drywall.
The channel should be screwed to all of the strips with drywall screws. Channel should be joined by overlapping them by a few inches with the corrugated webs nested together and BOTH base flanges screwed through to the strip beneath. A “pop” rivet would add extra security to the channel joint.
Drywall Installation: Furring strips are usually not required unless added dead air space is needed in the new wall/ceiling. A panel of 5/8″ “Firecode” Drywall, or similar composite (“Sheetrock, Plasterboard”, “Gypsumboard” etc), should be used and fitted to within ¼” of the surrounding walls/ceiling. Joints should be staggered in all directions. ALL joints should be secured to the resilient strip with the appropriate length screws close to their edges. Adding our tape to the channel pads the metal where it touches the wallboard. (If the panel is not covered with mat already).
Attaching: Secure the first of the material to be used to the resilient channel with the appropriate length drywall screws, making sure that the screws ONLY penetrate the corrugated web part of the resilient channel. IT IS ESSENTIAL THAT THE SCREWS ONLY PENETRATE THE CORRUGATED WEBS AND DO NOT COME INTO CONTACT WITH THE RESILIENT channel base SUPPORTS OR furring strips. Do not overly tighten the screws or they may pull through the thin metal channel. Just “snug” them.
Attach the second layer of material (drywall) using the correct length LONGER screws taking care to offset the joints of the first layer and screw only into the first layer of material, not into the resilient channel. (If not using a panel adhesive, a few screws may be put through to the channel if need be). A ball peen hammer will dimple the drywall for help in setting the screw heads. Do not break the paper facing of the drywall panels with the screws as a reduction of strength will result.
Edge Sealant: Flexible acoustical caulking compound that will remain flexible for years should be applied to ALL the edge perimeters after the installation of EACH layer to achieve optimum results.
All drywall joints should be finished with traditional jointing methods and plaster covered before painting/decorating in the normal manner. Do not heavily “mud” the gaps. (Tape and Paint). Protruding screws may be lightly tapped with a hammer and carefully tightened some more by hand. Do not break through the paper covering!
Resilient Channel: Part/Number: “RC-1”
Dimensions: Steel Gauge : .018
Weight : approx. 0.37Kg/m
Length : Cut for UPS shipping: ( 6€™)
Availability: Manufactured by “Unimast”. Check with them or your local Builders Supply for availability in 12′ length, otherwise order from us. (We cut to 6′ for UPS shipping:). We also have RC-2 and DWFC.
TIPS for Walls: Don€™t allow the drywall sheets to set directly on the floor. Use vibration pads made of ribbed neoprene and cork to place under drywall sheets for support when used for walls. Caulk well. Stagger joints. Use metal tape on underlying joints. Caulk well. Don€™t screw baseboard onto both the pads and the wall base sill.
When installing the channel over thicker mat (like 1″), don’t pull mounting screws down too tightly. This will deform the channel. Don’t break the paper of the drywall with the screw!
Remodeling a typical wall for average sound reduction: Apply Mass Loaded Vinyl (MLV) directly to the existing wall. (Two layers is best). Stapling will hold it temporarily in place. Now install at least one layer of 5/8″ firecode drywall over it. Tape off and paint. This will more than double the sound reduction of the existing wall.
Remodeling a typical wall for even more sound reduction: (Where existing wall has little or no sound blocking qualities). Take drywall off on one side, then the joists/studding, electrical boxes inside is caulked well and our 1/4″ acoustical mat is glued to the opposite inside wall and the exposed studding is covered, too. Our “Silencer” flooring (MLV) is stapled to the joists/studding, covering the ceiling/wall completely. Seams are sealed with caulk or tape. (Lead tape improves the seam seal). For an 8′ high wall, three RC-1 channels are installed horizontally over the wall, one in the middle, one at the top and bottom, located a few inches down to avoid the footer and header. Then 5/8″ “firecode” drywall (this is now also available with a lead foil covering) and is laid out on sawhorses and covered with a layer of the 1/4″ foam mat using contact cement and a roller. These panels are installed on the channels with screws and is supported by 2″ square vibration pads located every 2 feet or so. The bottom of the drywall is caulked tight and the seams too.
To help fill the gap and reduce the amount of caulk use “Backer Square”
Additional soundproofing material will increase the sound control ability of the wall in proportion to the type and amount added.
Be sure to cover the entire wall, no gaps left open. Gaps amounting to 2-3% of the wall covered can reduce the effectiveness of the job by 50%!
Due to vast differences in the care taken using these installation techniques, information contained in these instructions is given in good faith but without any kind of warranty.The EPA Manual has more information on this and other techniques.See our prices pages for product/cost information and availability or call for free consulting! 760-752-3030NEW! Sound Control Clips hold the panels better and are easier to install than resilient channel: Get more than double the STC of resilient channel! Call about the new SuperSound Clips!