Noise problems associated with flooring range in transmission from voices, television and music to footfall impact and plumbing. The proper installation of a sound reduction system during the construction process can be a proactive solution to help prevent issues that could otherwise be very difficult and expensive to resolve. 

“Soundproofing is an important element of commercial and residential buildings, such as apartments, condominiums, hospitals or offices,” said Dustin Prevete, senior product manager, Laticrete. These types of buildings require minimal impact noise from floor spaces above so they can provide quiet comfort levels for occupants.” 


Before working with sound control products, installers should carefully consider the building code requirements for the project’s jurisdiction to ensure that the appropriate sound reduction performance properties are achieved. To make an intelligent decision about what type of product to specify or install, it is important to understand what is required by the building code and what the performance standards of IIC and STC actually mean. 

“A product’s sound-reduction capabilities are typically measured by the products’ IIC rating, which determines how well a building floor attenuates impact sounds, such as footsteps,” Prevete said. “Likewise, Sound Transmission Class (STC) is another way to measure airborne sounds, which includes speech, music, television, traffic and other common daily sounds that can penetrate through flooring.” 

When determining which type of sound reduction product is most appropriate for the desired installation, Prevete said installers should begin by examining the targeted IIC rating required for the specific project. This rating is measured in an acoustic lab through a tapping machine with steel-faced hammers, which evaluates the sound-insulation properties of a building’s elements to determine the effectiveness of floor coverings in reducing impact sound transmission through concrete floors. 

Impact Isolation Class 

Impact Isolation Class (IIC) refers to the measurement used to quantify the transmission of impact sound through a flooring assembly. IIC sound is the equivalent of footsteps, dropped articles, or furniture being dragged across the floor. IIC is measured and tested for per ASTM Test Method E492. There is an additional IIC test standard for concrete subfloors defined by ASTM Standard E2179. This standard states the IIC rating as the ∆ (Delta), or contributed value for the underlayment and flooring and is meant to provide some clarity as to the actual performance of systems. If you are looking at ∆  IIC data, in most cases a ∆ IIC value more than 20 will be required to provide Code Compliance. 

Sound Transmission Class 

Sound Transmission Class (STC) refers to the measurement used to quantify the transmission of airborne sound such as laughter, voices, clapping, radios, etc., through building elements, such as walls or floors. STC is measured and tested per ASTM Test Method E90. 

Products for Sound Reduction 

Adhesives and underlayments both work to eliminate the transmission of substrate cracks from transferring to the finished floor. For some, adhesives are the preferred method for sound control because they take the place of costly, time-consuming underlayment mat systems, while experts say that underlayment sheet mats tend to work best under other types of glue-down finishes. 


“The advantage of selecting an adhesive that provides sound control is that you can simplify the installation method down to a single step,” said Jeff Johnson, business manager, Mapei. 

Replacing the need for costly, time-consuming underlayment mat systems, adhesives allow for faster, more effective tile or stone installations. Specifically, adhesive products are best suited for ceramic and porcelain tile finishes as well as natural stone. They are also ideal for renovation projects where finish heights have already been established due to their thinner system profile build up. 

However, Johnson notes that there are some disadvantages to adhesive solutions that installers should be aware of. “The disadvantage of a single-step adhesive solution is that it is limited to a single application of adhesive, which is driven by the requisite coverage required by the flooring type.” 


Adhesives are not ideal for all types of floorcoverings, and this is where underlayment mats come in. Underlayment mats for sound control often include a wide array of mat thicknesses and IIC values, making them possible to be used in all types of flooring projects rather than limited to tile or stone. As a rule of thumb, underlayment sheet mats tend to work best under other types of glue-down finishes, such as hardwood, making them more versatile when various finishes require sound control.  

Most recently, an overwhelming majority of commercial underlayment projects are installations using a recycled rubber underlayment, specifically in areas with large numbers of multi-story buildings because recycled rubber underlayment has proven performance over a longer period of time. 

In addition to taking the recycled content of a underlayment into consideration, experts suggest installers do their homework when selecting an underlayment, taking factors such as lab and field tests into consideration. And after sound considerations, installers are advised to look at other performance principles like the type of subfloor, moisture protection, compression resistance, whether or not the underlayment offers any thermal insulation for flooring and how it contributes to clean air quality.