Selecting Acoustic Flooring Underlayment for High-Density Housing
Under glue-down, nail-down or floating wood, laminate or luxury vinyl tile flooring, quality underlayment designed to improve acoustic properties can help reduce impact sound, dampen ambient sound and inhibit other sounds caused by voices, thumping music, loud TVs, door slams or footfalls.
Underlayment is available in a wide range of materials, including natural, synthetic or wood fiber, foam, cork and rubber. Some products are also approved for use over radiant heated floors – check with the manufacturer and do not assume. Additionally, the North American Laminate Flooring Association (NALFA), a trade organization made up of flooring and underlayment manufacturers, has created commercial and residential standards for underlayments. The NALFA Certified Underlayment seal means the product passes stringent testing set forth by the member laminate flooring manufacturers.
During the planning stages of a project that includes new flooring, owners of new and renovating multi-family housing should make sure their architects, designers or contractors specify acoustical floor underlayment that not only meets local building department standards for sound attenuation but, wherever financially viable, exceeds local code. Code is usually the minimum any housing project owner would want to build to.
Minimum acoustical codes were written many years ago to minimize sound transmission between floors in low-cost HUD housing and eventually were adopted by the International Building Code (IBC). Today, buyers and renters alike in upscale or even middle-income units in multi-family projects expect a greater degree of relative quiet. One good way to evaluate the effectiveness of a manufacturer’s claims as to how well the underlayment addresses sound attenuation is to look for testing results provided by third-party lab testing. Manufacturers who take the effort to and bear the expense of following this route will likely make that information readily available in company literature, on company websites and on the product packaging itself.
The IBC recognizes two tests performed in a controlled laboratory environment of the floor/ceiling assembly (not just a single component) for sound that travels from one living area down to another, including in a multi-family residential complex: Impact Insulation Class (IIC) and Sound Transmission Class (STC). IIC tests the ability to block impact sound by measuring the resistance to transmission of impact noise or structure-borne noise. STC evaluates the ability of a specific construction assembly (e.g. floor, window, door) to reduce airborne sounds, such as voices, stereo systems and TVs. The tests are often considered essential tools for evaluating sound in multi-level dwellings.
An IIC rating of 50 satisfies IBC requirements but does not necessarily placate tenants, who, with only that level of insulation in the floor/ceiling assembly, likely would still notice and call the landlord about intruding noise. Flooring components that, put together as a floor-ceiling assembly, achieve a higher score – e.g. 57 or 58 – would reduce the likelihood of complaints.
Field tests (FIIC) for the same properties may be conducted in an actual building, after the flooring is installed, sometimes called for by building departments to show the flooring assembly complies with the acoustic code requirements. The IBC requires a rating of at least 45 in this test. But again that is just a minimum requirement. Underlayment that, in certified field sound tests in an installation over a standard concrete subfloor, receives a score in the upper 50s will buffet sound transmission much more effectively than the bare minimum to reach the building code.
Some sound-attenuating underlayments have additional attributes that would be attractive to environmentally aware owners and tenants—including that they are made from recycled materials such as textile fibers diverted from landfill, and/or meet LEED standards for low emissions and may help a floor assembly contribute to earning LEED credits in the categories of Materials and Resources and/or Indoor Environmental Quality. These features, like sound test results, are also typically indicated in manufacturer literature.
Look for other seals awarded by independent testing labs, such as Scientific Certification Systems (SCS) which not only certifies recycled content but also tests for any off-gassing or volatile organic compounds (VOCs) which can cause potential health problems. The SCS “Indoor Advantage Gold” certification clears the way for products to be installed in hospitals, schools and government buildings as a contributor to clean air.
Installing a flooring assembly that is based on overall value, not just price, and minimizes sound transmission between floors not only makes for better neighbors but good business sense. To that end, acoustical underlayment with strong sound-deadening features would be a very valuable component of new flooring in multi-family residential projects, quietly benefitting residents and owners alike for the life of the installation.
Jack Boesch is the director of marketing at MP Global Products, a Norfolk, Neb.-based manufacturer of fiber acoustic underlayment for hard surface flooring. For more information, visit www.quietwalk.com or call (888) 379-9695.