• The Consequences of Cutting Corners


    We’ve all been there—whether it’s running late to work, trying to get out in front of the afternoon rush, or even replacing a few words in a text message with an emoji to save some time. Taking shortcuts is part of our everyday life. We strive for efficiency and speed, sometimes just racing the clock when we can’t find an actual opponent. “Get in, Get it done, and Get out” is more or less the catchphrase for every type of task most of us will encounter in our day.

    Construction can relate to this shortcut culture—maybe more than any other trade. With jobs, timing, and collectively billions of dollars on the line, speed is key. So, why wouldn’t we take a shortcut at every available opportunity? The advantages of a shortcut are sometimes too tempting to ignore. Unfortunately, the repercussions of them often set us back further than it would to if we stayed on the specified path. Unintended outcomes and unpredictability are the two most likely outcomes of shortcuts, and also some of the most damaging results in construction. Look no further to noise control systems for a real-life view of how shortcuts can lead us down the wrong path.


    Shortcuts for STC Standards

    In multi-family construction, there are codes that exist to help govern the amount of noise that can pass from unit to unit. Both walls and floor/ceiling assemblies must be designed and constructed well to meet these expectations. If not done, not only will the code not be met (or at least the performance diminished), but neither will the expectations of the occupant. As we increasingly move into higher density living conditions, noise control is one of the most talked about issues in multi-family. If our goal is to improve upon this, we need to design products to mitigate issues caused by taking a shortcut or even better products designed well enough so that there is no need to look for one.

    STC is the ASTM Standard for measurement of airborne sound from unit to unit. Examples of this are easy to imagine: human speech, television, music, etc. The generally accepted approach to increase the system's STC performance (wall or floor/ceiling) is to add mass. Gypsum board is a massive form of a cement board that helps as it pertains to flame spread and does a considerable amount of assisting in the acoustics of the wall assembly. The heavier the wall or floor, the better the performance. Details such as the treatment of the electrical outlets and other wall penetrations are critical to ensuring the marketed performance of the wall system. As it is easy to imagine, the best passageway for sound to travel easily is through air.



    The specified 1/8-inch gap between the ceiling board and wallboard at every intersection. The standard detail would be to use an acoustical caulk (expensive and time consuming) to fill that gap, then to tape, and mud that joint.


    Wouldn’t it be a lot easier to just skip the caulking? Why even work so hard to create a gap in the first place when all I intend to do is fill it?


    Every hole in our wall is a detriment to the system and needs to be treated with care. Without caulking, that gap has become a passageway for noise to travel, thereby creating the unintended consequences of a louder wall.


    A good designer and/or manufacturer can anticipate these shortfalls in execution and design systems that incorporate products to prevent these from happening. Keene Building Products’ Space Assurance™, a 4-inch wide non-combustible polyester strip, is a great example of this. Space Assurance™ is installed at the top plate of the wall with staples prior to the installation of the ceiling board. Next the excess material is folded under the ceiling board and the wallboard is slid into position. The fabric compresses to 1/8-inch in thickness creating that designated gap while filling it at the same time. The excess is trimmed, and the joint is taped and mudded, as it typically would be. Space Assurance™ is a great example of building smarter, not harder.


    Shortcuts for IIC Standards

    Moving down to the floors, again the performance is in the execution. The type of sound we are concerned with, however, is slightly different than in the walls.

    IIC, short for Impact Insulation Classification, is measurement of the vibrational noise—think a stomping sound—that passes from the floor to the ceiling below. Isolating the assembly or creating less connection points for the vibration to travel from one surface to the next best controls this type of noise. All the acoustical products in the marketplace are designed around this being the case with the best installation methods clearly denoting this.



    The drywall contractor is responsible for installing the RC-1 channel, a 1-legged resilient furring channel, and the gypsum board ceiling to the bottom of the joist. The standard detail of installation is to measure off all the joist intersections and to use a 1-inch specified screw length to attach the boards in the channel. This is an incredibly difficult thing to do quickly and consistently.


    Wouldn’t it be faster to not have to measure? A longer screw would make it a whole lot easier to attach the boards, why not just use those?


    Shortcuts would indeed make the job a lot simpler, but can significantly decrease the ability of the floor/ceiling to limit impact sound. This is due to a term most commonly referred to as short circuiting, meaning the installation had been compromised by penetrating the screw (due to placement or length) through the channel and into the joist. Each short circuit is an additional path for vibration to travel thus the system is noisier.


    An easy and inexpensive solution is to utilize a clip to prevent this from happening, no matter how haphazard the installation process is. All other vibration isolation clips available on the market today are limited in their application, since they typically only work with “Hat” type resilient channels. Luckily, Keene’s patented Cylent Assurance™ Clip (vibration isolation clip) can work with any type of standard resilient channel, including both Hat and RC-1 channels, to significantly reduce low frequency noise transfer in ceiling/wall assemblies used in modern multi-family construction.


    Build Smarter, Not Harder

    These solutions and more are available to designers and contractors alike to help preserve the performance of their systems. Planning for these shortcut situations ahead of time is the best way to avoid unexpected outcomes while speeding up the process at the same time. The updated Sound & UL Chart in our new Acoustic Product Guide includes job-specific acoustical testing that can make planning a bit easier. By attempting to build smarter with well-designed products, we will eliminate a whole host of these nagging issues with little left up to chance.

    Sounds good, doesn’t it?

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