Q: Can I use different types and thickness of wallboard than those listed in the instruction booklet?

A: Yes, but be sure to use different types and/or thicknesses for each of the two layers so that you don't double-up on any natural resonances associated with a particular wallboard.

Q: I've heard you're not supposed to put moisture resistant wallboard on ceilings. Is this true?

A: You can use MR board (green board) on ceilings as long as the framing members are sufficiently close to one another. In the case of the Iso-Wall system, the framing members for the wallboard are the resilient channels. If you are using 1/2" moisture resistant board as currently recommended in our instruction booklet, then placing the resilient channels no more than 12" apart, as stated in the ceiling instructions, is sufficiently close according to the 2000 USG Construction Handbook. If you are planning on using 5/8" moisture resistant board on the ceiling, then you will need to adjust your system to place the resilient channels no more than 16" apart to be sufficiently close.

Q: The installation instructions require that I attach the ceiling Perimeter Gasket to the nailer plate above the top plates on the wall, but what if my walls don't have a nailer plate above the top plates?

A: In this case, you will need to place blocking between the ceiling joists at the perimeters of the ceiling. This will give you a continuous framed perimeter for attaching the ceiling Perimeter Gasket.

Q: Your instructions state that I should use insulation blanket with no paper or foil backing. Why is that?

A: Two reasons. First, it is best to avoid the possibility of the paper or foil surface ever coming in contact with the resilient channel. This could create a situation where there may be a slapping sound heard from the vibration of the channel against the thin membrane. Second, we want to keep the air-flow chamber as large as possible directly behind the wall. This allows deeper breathing ability and, hence, greater overall effectiveness.

Q: What if I need to have foil or paper backing on my insulation or use a separate type of membrane as a vapor barrier?

A: If you need to have a vapor barrier, you have several options. First, if you can use insulation blanket with foil or paper backing, place the backing away from the interior of the room (see the FAQ immediately above) for which the Iso-Wall system is being applied. If you must place the backing toward the interior of the room, use wire insulation supports (as suggested in the instructions for wall installation step [1] ) to hold the backing at least 1inch away from the resilient channel. Second, if you need to use a sheet of visquine or other material to cover the entire wall, place it on the opposite side of the frame from the side for which you are applying the Iso-Wall system. If you must place the material on the interior side of the frame, place it separately over each stud cavity, tucking the edges into the interior of the cavity and attaching it to the sides of the studs . This leaves the stud faces exposed for placement of the Iso-Wall system. Be sure to tuck the material far enough into the cavity so that it is no closer than 1 inch away from the resilient channel at any point (see FAQ immediately above). If you are applying a vapor barrier to conform to building code, you may be able to get the Iso-Wall system itself to be considered an acceptable vapor barrier by your building inspector. If you are using the 2 layers of wallboard, including moisture resistant board, 1/2" gasket, and acoustic sealant as directed in the installation instructions, you have built an air/moisture-tight seal on that surface. This is what is required for an acceptable vapor barrier. We have at least one confirmed case of a building inspector approving our Iso-Wall system as an acceptable vapor barrier in a new construction home.

Q: I have a recording studio and I want to have a cable pass-through built into the wall. Can I do this and still use your Iso-Wall system?

A: Yes, and, in fact, we can even help make your cable pass-through better suited for use in combination with the Iso-Wall system.

Q: Can I use cement board or limp mass barriers with the Iso-Wall system?

A: Yes, you can use more massive wallboard or additional layers of extra mass with the Iso-Wall system. Be sure to place the resilient channel more closely together to provide the extra weight support needed, if you do this. It is important to note, however, that the individual sound blocking abilities of different materials do not simply add to one another. For example, a layer of mass-loaded vinyl may have an independent STC rating of 30dB and your existing wall may also have an independent STC rating of 30dB, but when put together you will NOT achieve an STC of 60dB. Doubling the mass of a wall will typically increase the soundblocking power by 2 to 4dB. So, for the previous example the resulting STC would most likely fall between 32 and 34dB.

Q: How do I build light switches and electrical outlets into the Iso-Wall system?

A: Every room has its own unique configuration and we defer the exact solution to the expertise of the on-site builder/contractor. However, as a general rule, electrical outlets usually occur around 10" off the floor. This places them between the bottom resilient channel and the second resilient channel up from the floor. You should offset junction boxes to take into account the additional thickness of the resilient channel and 2 layers of drywall, as well as the small thickness added by the layers of Wall Damp material, making the total wall thickness in the range of 1-3/4 inches. It is recommended that you leave a 1/4" gap between the edge of the box and the wallboard that should be sealed with acoustic caulk, identical to the edges of the wall. Face plates can be screwed tightly to the boxes once the caulking has had sufficient time to dry. For light switches, you should plan ahead so that appropriate adjustments to the resilient channel spacing can be made to avoid interfering with any junction boxes. Built-in lighting on the ceiling can be addressed in a similar fashion. Note: some preliminary research findings have indicated that there may be a possible small improvement to the sound-blocking power of a wall by using plastic junction boxes instead of metal ones.

Q: How can I further enhance my Iso-Wall system?

A: Optional additional steps you can take are to:

1. Apply the optional Wall Damp application, shown at the end of the installation instructions, to the opposite side of the wall (interior walls only)
2. Add ASC Stud Stabilizers to the framework or stabilize the framework by attaching it to concrete walls or foundation
3. Use larger studs and joists and fill the cavities with thicker insulation (e.g. use 2x6 with 5" insulation fill vs 2x4 with 3" insulation fill)
4. Place your layers of wallboard perpendicular to one another (i.e. put one layer on vertically and the other horizontally)
5. Put extra Wall Damp strips on the first layer of wallboard wherever you project the second wallboard layer seams will occur
6. Use a staggered stud or double stud frame design.
7. Use ASC Wall Wool Batts in place of standard fiberglass insulation.
8. Use acoustically absorptive wall panels to reduce the level of high-frequency reverberation within the room containing the sound source.
9. Use steel framing.

Q: Can I put the Iso-Wall system on the floor?

A: No, although Wall Damp material can be used in the construction of a floating floor to isolate sound transfer through that surface. Generally, if you are trying to improve sound blocking power through the floor, you should apply the Iso-Wall system to the ceiling in the space below. If you wish to add a floating floor or riser to the room, we can provide recommendations for construction using WallDamp materials. Contact us at 1-800-272-8823 for more information.

Q: Can I use a layer of Plywood in the walls with the Iso-Wall system?

A: It is OK to use plywood as the first layer of the IsoWall. Apply WallDamp as usual. We normally prefer using gypboard because the gyp is heavier than plywood of the same thickness which allows the possibility for greater mass in a smaller space. But it can certainly be done using plywood. You can put gypboard over the plywood if you wish to make up for any lost weight.