Tag Archives: acoustics

Improving Floor/Ceiling Sound Control in Multifamily Projects: Sound Testing Practices

by Josh Jonsson, CSI

The sound transmission class (STC) and impact insulation class (IIC) are ASTM-derived single number ratings that try to quantify how much sound a stopped by partition being tested.

Laboratory testing involves an ideal setting for the floor/ceiling assembly—it is isolated from the walls, and there are no penetrations for HVAC, plumbing lines, sprinklers, can lights, or electrical boxes. In the field (i.e. F-STC and F-IIC), the floor/ceiling assembly often sits on load-bearing walls, is connected to the structure, and contains many ceiling and floor penetrations for the items just mentioned. Consequently, the code allows for a lower rating for field scores over those in the lab.

The STC rating essentially tells how much noise is stopped from going through a wall. The test involves blasting loud noise at all the measured frequencies in a room. A Level 1 sound meter measures this exact noise in that room level at all frequencies, as well as the sound in the room on the other side of the partition. These two different levels are then essentially subtracted from each other, with some corrections made for background noise.

The IIC rating is not a comparative test like the STC. Rather, it uses an ASTM-specified tapping machine that sits directly on the floor—more specifically, directly atop the finished floorcovering. (Consequently, an IIC rating always lists the floorcovering with which it was tested.)

The machine has five steel hammers that spin on a cam shaft, falling onto the floor from the same height, no matter what or who is testing. These hammers put a consistent energy into the floor. The sound level meter is taken downstairs below the tapping machine and the sound level is measured at all the frequencies called out in the ASTM standard. These sound levels are plugged into the equations in the standard; a single number is generated summarizing how much sound was stopped.

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Improving Floor/Ceiling Sound Control in Multifamily Projects

DSC_1207-2

All images courtesy Maxxon Corporation

by Josh Jonsson, CSI

In recent years, demand has increased for better floor/ceiling acoustics in multifamily construction. This has been driven by consumer desires, new guidelines from code bodies, and stricter enforcement of existing codes. How do design professionals keep pace as the traditional approaches to multi-unit residential sound control evolve?

This article reviews important new guidelines that must be taken into account by architects and specifiers, and examines how construction manufacturers have created new products or enhanced existing ones in the pursuit of achieving higher acoustical performance.

Thanks to product technology improvements and more stringent regulations, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly.

Thanks to product technology improvements and more stringent regulations, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly.

Two of the principal measurement standards for acoustics in multifamily construction are:

  • sound transmission class (STC), which pertains to the amount of airborne sound contained by a given building element (i.e. walls, doors, windows, and floor/ceilings); and
  • impact insulation class (IIC), which deals with impact noise (i.e. footfall, chair scrapes, and dropped objects) transmitted through a floor/ceiling system.

Both these single-number ratings apply to the full assembly of building materials used to separate tenants, including floor/ceiling assemblies.

For more than 50 years, these measurements have helped architectural project design teams quantify the acoustic levels of floor/ceiling assemblies. In fact, the Department of Housing and Urban Development (HUD) wrote A Guide to Airborne, Impact, and Structure Borne Noise: Control in Multifamily Dwellings in 1967, helping reinforce the importance of sound control in multifamily construction. This document, along with the Uniform Building Code (UBC), helped project teams recognize an acoustical threshold was needed in multifamily construction. UBC required an STC and IIC rating of 50 (or 45 if field-tested as F-STC or F-IIC). The higher the rating, the better the performance. (See “Sound Testing Practices.”)

In 1997, UBC gave way to the International Building Code (IBC) as the widely accepted model code. This shift brought greater awareness of acoustical ratings and their deemed thresholds in unit-over-unit construction, however these code levels remained aligned with the UBC’s established minimum requirements of STC and IIC 50 (or 45 if field-tested).

As the multifamily industry became more competitive, developers began offering upgrades in flooring and lighting to tenants as an amenity, yet little to no attention was paid to acoustical performance. This is astounding when one considers acoustics continue to be one of the driving factors in maintaining low vacancy levels, as well as one of the most litigated issues in this type of construction. To compound the subject, many of the amenity upgrades offered, such as hard-surfaced finished floors and canister lighting, can adversely impact a floor/ceiling assembly’s performance.

CS_July_2014.inddUpdating acoustical recommendations
In response to the need for updated acoustical guidelines, the International Code Council (ICC), along with several respected acoustical experts, created ICC G2-2010, Guideline for Acoustics. The guideline recognizes:

the current level and approach of sound isolation requirements in the building code needs to be upgraded. The requirements are currently insufficient to meet occupant needs.

As shown in Figure 1, the guide provides two levels of acoustical performance: ‘acceptable’ and ‘preferred.’ Both exceed code minimums for airborne and structure-borne noise.

These new levels now give a clearer direction on what levels should be targeted for desired acoustical performance, depending on the building type. As the names suggest, when one wants a building that has an acceptable level of acoustical separation, ‘acceptable’ is targeted. When one is designing a building on the higher end of market rate or luxury level, or has tenants or owners sensitive to noise, the desire should be for a ‘preferred’ level of performance.

Components of acoustical design
How do these new recommendations apply to the current approach for multifamily construction? As Figure 2 shows, a commonly specified design for many multifamily projects, which is also recommended by acoustical consultants, includes:

  • hard-surfaced flooring;
  • 25 mm (1 in.) or more of gypsum concrete;
  • 6.4-mm (¼-in.) entangled mesh sound mat;
  • wood subfloor;
  • wood floor trusses or joists;
  • insulation;
  • resilient channel; and
  • one layer of gypsum board.

CS_July_2014.inddThe typical rating for the design would be an IIC 51 to 55 and STC 56 to 60, depending on the floorcovering (e.g. laminate, tile, floating engineered wood), the acoustical performance of which would be listed by the consultant and verified by test reports. These numbers exceed code minimum and exceed the STC requirement for ‘acceptable,’ but only marginally—at best—meet an ‘acceptable’ level for IIC and any nuisance impact noises from upstairs tenants (IIC).

It is important to keep in mind these listed ratings would be achieved by selecting and installing all the components based on proper acoustical design. For example, the resilient channel would need to be a product similar to a proprietary one using steel measuring 0.5 mm (0.021 in.) thick by 38 mm (1.5 in.) wide, as opposed to a similar but lesser design lacking proper acoustical performance. To increase the IIC rating, an upgrade to the sound mat and/or the resilient ceiling system must be made.

Improving IIC ratings with sound mats
Traditional sound control mats with entangled mesh enhance IIC performance through the mesh being attached to fabric, which is loose-laid over the subfloor and then encapsulated with a gypsum concrete topping. The entangled mesh acts as a spring and produces an air space with little surface contact (i.e. three to five percent). Until recently, IIC performance was upgraded by using a thicker sound mat and deeper gypsum concrete.

Sound mat manufacturers have added new technology that allows for higher ratings while continuing to meet industry expectations for the corresponding thickness of the gypsum concrete. Traditional entangled mesh mats are now being manufactured with an additional acoustical fabric—Figure 3 depicts a 6.4-mm (¼-in.) entangled mesh mat with this upgrade. The acoustical fabric is laminated to the underside of the mat, creating an additional vibration break and absorptive layer. This improved product requires the same thickness of gypsum concrete as its standard counterpart. The IIC performance of the system is improved by two to five points without adding any measurable thickness to the floor system.

Another option is to employ the original 6.4-mm entangled mesh sound mat and a secondary topical mat placed between the gypsum concrete and the finished floor. If this option is selected, this secondary mat should be high-quality and thoroughly tested for sound ratings. (The sound test showing this type of product’s performance must be specific to the assembly that is being used versus a sound test from an unrelated design—for example, using concrete test data for a 2×10 joist system.)

CS_July_2014.inddImproving IIC ratings with resilient clips and channels
Properly installed, high-quality resilient channel will improve IIC ratings, but the resilient channel’s effectiveness can be easily lessened through faulty installation. To install traditional resilient channel, proper-length screws are imperative so as not to penetrate the joist or remove the channel’s resiliency.

Penetrations from the drywall into the joist through the resilient channel create flanking paths that transfer sound through a floor/ceiling assembly, as does having a channel affixed tightly to the assembly. For these reasons, new resilient clips that are difficult to install improperly have been introduced to the market. These clips can deliver equivalent performance to properly installed, high-quality resilient channel.

Hanging systems that provide spring and reduce or eliminate resilient channel contact with the joist offer even better performance. Figure 4 shows two such products: the ceiling wave hanger and a spring isolator. Either of these products installed in conjunction with a 6.4-mm (¼-in.) entangled mesh sound mat on the floor above would help the system exceed the ‘acceptable’ level, and approach ‘preferred’ levels for the IIC rating with hard-surfaced floorcovering. See Figure 5 for various assemblies and their acoustics attributes.

How to design for desired acoustical performance
As a specifier or architect team leader, one must first determine the level of acoustic performance to which to design. This should not be a matter of just meeting code—rather, the entire conversation must be approached in a new light. The following questions should be asked:

  1. When considering the amenities offered to tenants, how important are the acoustics of the unit? In other words, how important is the quality of life related to acoustical privacy?
  2. Does the project team want to just meet code because complaints and vacancy rates are unimportant or not a factor? Do they want ‘acceptable’ performance, significantly reducing noise complaints and removing sound control from the vacancy equation? Or, do they want ‘preferred’ performance to meet client expectation and greatly reduce potential for noise complaints?
  3. Once the level is determined, which method makes the most sense for achieving that performance level? Does the sound mat get upgraded to a very high-performing mat (manufacturers offer many styles with differing performances)? Does the sound mat get upgraded while keeping the system as thin as possible? Does the sound mat stay the same and the ceiling hanger system get upgraded? Is a secondary sound mat added while upgrading the primary sound mat and/or ceiling system to reach optimal sound ratings? Or, do the mat and ceiling get upgraded to reach better ratings?

CS_July_2014.inddEven after the desired level of performance has been determined, there are other factors that should be considered, such as whether the project will always be apartments or if they could become condominiums. There is also the matter of whether carpet and pad areas will always have carpet and pad.

Projects that start as apartments and then plan on being converted into condominiums should be approached as if they were condominiums from the beginning. Future owners may tear out carpet and replace it with hard-surfaced flooring.

Sound mat manufacturers receive a high volume of phone calls every year where a condominium project put sound mat only in the hard-surfaced areas. The new owners want hard surfaced flooring throughout and are being told they need to provide levels of performance similar to the ‘preferred’ levels while only being able to add a thin amount to the profile of the floor. As they can only do work in their unit, they are left trying to use a thin, lower-performing sound mat to reach the requested, more stringent criterion.

Acoustic qualities of various fl ooring assemblies.

Acoustic qualities of various flooring assemblies.

Conclusion
Throughout the United States, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly. Innovative architectural acoustic products continue to see greater use in existing metropolitan areas as well as in new areas of the country. It is important specifiers continue to be educated on new products and adapt their specifications to ensure they meet defined levels of sound control that tie directly to the end user’s satisfaction with their living space.

Josh Jonsson, CSI, is an acoustical specialist and West regional manager at Maxxon Corporation. He has more than 15 years of experience in the architectural noise industry and has worked for acoustical and vibration consulting agencies. Jonsson is a member of CSI, Acoustical Society of America (ASA), and ASTM International committee E33 Building and Environmental Acoustics. He can be contacted via e-mail at josh@maxxon.com.

Shapes and Sounds: Designing concert halls with curves

Images courtesy Radius Track Corporation

Images courtesy Radius Track Corporation

by Chuck Mears, FAIA

The marriage of shape and sound are used to create world-class acoustical experiences inside the New World Center, designed by Frank Gehry, and the Kauffman Center for the Performing Arts, designed by Moshe Safdie.

Billowing clouds, curved ceilings, and swooping lines all have dramatic impact on the way concertgoers experience sound. Both architects relied on the use of curved surfaces to diffuse sound and to create the distinctive appearances, each with dramatically different visual results.

Technology has changed how spaces are designed. This image is a 3D framing model for an acoustic ceiling.

Technology has changed how spaces are designed. This image is a 3D framing model for an acoustic ceiling.

Gehry chose to expose the curved elements, enclosing them in a glazed box that allows passersby to glimpse the flowing interiors. Safdie used giant curves to define the shape of his building, composed of two symmetrical half shells of vertical concentric arches, which perch on a magnificent site overlooking the city. However, in both cases, the ability to interpret the acoustician’s nuanced instructions to exacting perfection was the key to creating an acoustical masterpiece in two of the United States’ most important symphonic institutions.

This article deconstructs the delicate balance between shaped walls, curved ceilings, and sound—principles that can apply in any performance space.

A look back in time
Concert halls have historically been designed with the architectural trends of the day. The science of architectural acoustics is just over a century old, but before it was hit or miss. Many of the early European halls, which were heavily ornamented on the walls and surfaces, were fortunate accidents, as the ornamentation served to diffuse sound.

It was not until Wallace Clement Sabine, an assistant professor at Harvard, was called on to correct an acoustically disastrous lecture hall on campus that modern acoustical science was launched. Sabine was able to determine, through experimentation, there is a definitive relationship between the quality of the acoustics, the size of the chamber, and the amount of absorption surface present. In 1898, he formally defined ‘reverberation time’—still the most important characteristic currently in use for gauging a room’s acoustical quality—as the number of seconds required for sound intensity to drop from the starting level by an amount of 60 dB.

In the 20th century, with growing popularity of ticketed concerts, many cities decided to build large-capacity venues, basing them on the parallelepipic form employed in some churches. The first reference model, called the ‘shoebox,’ places the orchestra directly in front of the audience; with musicians and spectators face-to-face. When designing for this type of architecture, acousticians must consider the shape and volume of the auditorium, and the materials used to achieve the ideal acoustic experience. What volume is required? How should the room be shaped?

Most auditoriums built since the 1950s have reproduced or adapted the shoebox model, which has the advantage of being well referenced, and therefore mastered by acousticians. However, contemporary architects like Safdie and Gehry are redefining the old models, and acousticians are learning new ways to incorporate complex design trends with the current knowledge base of acoustical engineering.

Designed by Moshe Safdie, the Kauffman Center for the Performing Arts’ prosceniumstyle Muriel Kauffmann Theater brings world-class cultural events to Kansas City, Missouri. Shown here are both early framing and completed work.

Designed by Moshe Safdie,
the Kauffman Center for the
Performing Arts’ prosceniumstyle
Muriel Kauffmann Theater
brings world-class cultural
events to Kansas City, Missouri.
Shown here are both early
framing and completed work.

IMG_6995IMG_0532The sound (and reverberation) of music
On a clear summer night, an outdoor concert can be entrancing. However, entering a well-designed concert hall can be even more magical, as the audience is enveloped in the music. This is because sound in a concert hall is related to vibrational energy.

Sound results from pressure fluctuations that travel through the medium of air. Various sources, such as an opera singer, a viola, or a horn, generate the air vibrations. The vibrations occur at varying rates, resulting in different frequencies of sound, which are perceived by humans as different pitches.

Low-pitched sounds (like that produced from a bass drum) vibrate at low frequencies, such as 20 to 250 cycles per second, or hertz (Hz). High-pitched sounds (like that of a piccolo) vibrate at high frequencies, such as 5000 to 20,000 Hz. Generally, humans can hear sounds from 20 to 20,000 Hz. These vibrations emanate in sound waves, which travel around the room, becoming reflected, absorbed, or transmitted at the walls or boundaries of the room. This is why the shape and size of the space, background noise, reverberation, as well as its material properties, are important.

In an enclosed environment, sound reflects—or reverberates—for a period after a source has stopped emitting sound. A space with a long reverberation time is known as a ‘live’ environment. Conversely, when sound dies out quickly, it is called a ‘dead’ environment. Speech is best understood in the latter, but music can be enhanced in the former, as the notes blend together.

Adding to an acoustician’s checklist are the different types of music that will be played in a space, as many venues today accommodate various styles. Reverberation time is affected by size and amount of reflective or absorptive surfaces in a space, making it one of the key considerations in a concert hall’s overall design and architecture.

For the Kauffman Center, form meets function—curves are both expressive aesthetic and carefully considered acoustic component.

For the Kauffman Center, form
meets function—curves are both
expressive aesthetic and carefully
considered acoustic component.

IMG_2816IMG_0591

Kauffman Center for the Performing Arts
Kansas City, Missouri’s Kauffman Center landed the Midwestern city among the ranks of world-class theaters like the Berlin State Opera in Germany and Disney Concert Hall in Los Angeles. The approximately 26,500-m2 (285,000-sf) facility has two technically sophisticated performance spaces: the proscenium-style Muriel Kauffman Theatre and Helzberg Hall.

With a seating plan similar to the traditional horseshoe of opera theaters in Europe, the Muriel Kauffman Theatre houses an acoustic infrastructure disguised within the aesthetics of the space, and showcases the integration of the architectural imagination with acoustical engineering.

Architect Moshe Safdie wanted the audience to experience a sense of warmth and intimacy with the performers. Referencing the fanning element of the facility’s north façade, the Muriel Kauffman Theatre curves around the seating pit and balcony; it naturally focuses sound waves to each of the 1800 seats.

Also pictured on page 10 and the cover, Helzberg Hall is one of the performing arts spaces in the Kauffmann Centre. Acoustic bumps were used behind an acoustically transparent mesh.

Helzberg Hall is one of the performing
arts spaces in the Kauffmann Centre.
Acoustic bumps were used behind
an acoustically transparent mesh.

CS_Helzberg_bumps

 

 

The seats were built with materials that narrow down the range between sound reflectance and absorption when occupied and when vacant—a difference of only 0.2 seconds. At the same time, semi-cylindrical bumps were installed behind the louver wall to balance out the acoustical focusing caused by the round shape of the theatre. Further, shallow balcony overhang design helped deliver direct sound to the audience from the stage. In this balancing act of absorption and reflection, shapes and textures have everything to do with the sound quality.

Similar to their design for the Muriel Kauffman Theater, Nagata Acoustics (Los Angeles) designed cylindrical, convex, acoustic elements behind acoustically transparent materials for 1600-seat Helzberg Hall. Similar to drawing a curtain on a messy room, these barriers conceal the bulky framework of an acoustical system, but do not stifle their acoustic properties. As captured so elegantly through Safdie’s design, acoustical materials are no longer an aesthetic obstacle for the architect.

Continuing in Helzberg Hall, architects and acoustical engineers worked against the challenge of maintaining sound intimacy in the face of a large expanse between the audience and performers. By devising a round room in which all the surfaces work together to reflect sound three-dimensionally, the team could channel the direct and clear sound reflections to each audience member.

Surface materials were a key part of the acoustic design in both performance spaces at the Kauffman Center. To channel quality acoustics up to the balcony from the Helzberg Hall stage, Safdie designed a shallow overhang to reflect the sound. Made of plaster with a sandblasted finish, the balcony’s surface materials are essential to the theatre’s ability to diffuse sound.

Performance Contracting Inc. (Lenexa, Kansas) worked with the curved cold-formed steel (CFS) framing provider to devise an advanced, structurally engineered framing approach to support the per-square-foot weight of the plastered acoustic surfaces, which included more than 907,000 kg (2 million lb) of acoustical plaster.

For Helzberg Hall, these curved framing members were engineered to shape and load requirements for acoustic elements that span nearly 30 m (100 ft) from the rear of the stage to the ceiling.

For Helzberg Hall, these curved framing members were engineered to shape and load requirements for acoustic elements that span nearly 30 m (100 ft) from the rear of the stage to the ceiling.

This weight of plaster was used to keep sound from transferring. To achieve this, the plaster on the ceilings had to be 63.5 mm (2 ½ in.) thick to meet the STC rating—1.2 to 1.4 kPa (25 to 30 psf). With nine different density requirements across varying plastered surfaces inside the concert hall, the geometry had to be perfect.

The process of tuning a musical venue has evolved from a ‘close enough’ mentality to extremely precise acoustical methods. In this case, the team’s process used 92 mm (3 5/8-in.) pre-curved studs tied to 19-mm (¾-in.) pre-curved cold-rolled channel framing to provide a precise and acoustically specific profile. Additionally, the perimeter of each of the acoustic elements created with the stud-channel framing methodology was finished with a custom-formed 110-mm (4 3/8-in.) track to provide crisp, clean edges and corners.

Kauffman’s complex geometry required an acoustic design complete with ‘bumps’ of various sizes in specific locations in each hall. For these elements too, the CFS framing provider prefabricated a complete kit of required parts, which was shipped to Kansas City and easily assembled onsite, reducing jobsite labor and installation time.

New World Center
Nagata Acoustics was also involved in the New World Center—Gehry Partners’ Miami project that used billowing shapes and acoustic clouds to render perfect pitch for the main performance space and practice rooms. Home to New World Symphony, the facility provides the noted orchestral academy with the space to “prepare highly gifted graduates of distinguished music programs for leadership roles in orchestras and ensembles around the world.” The centerpiece of the building is an adjustable 757-seat natural acoustic performance space, featuring large, distinctive sail-like acoustical surfaces designed for the ultimate orchestral experience.

Although New World Center is comparable to Helzberg Hall in its stage size and program capacity, the size of the room is smaller. Acoustically, this means less distance between the stage and the audience; therefore, the reflective surfaces are closer.

Sound in a compact space can be perceived as louder. By increasing the ceiling height to 15 m (50 ft), the room volume expanded and the level of sound decreased. The room, and consequently its sound, can be adjusted to a dazzling array of options, as Frank Gehry designed 14 different stage configurations within the hall’s trapezoidal shape. Seats can be retracted to add floor space and satellite platforms allow for performances off the main stage.

Five huge acoustic sails were among the primary tools Nagata’s acousticians used to focus sound. The sails are the focal point of the stage and also serve as video panels that enhance the concertgoer’s experience. The team was challenged to maintain the architectural ‘swoops’ of Gehry’s design and make it work acoustically. Some modifications were made to improve acoustics: tilt angles were adjusted, curvatures were changed slightly, and other tweaks were incorporated to deliver early reflections to the audience.

Such precision meant the CFS framing provider—working closely with Lotspeich Company, the specialty contractor responsible for metal stud framing, drywall, gypsum plaster, acoustical plaster, acoustical ceilings, and wall panels—had to be geometrically precise in fabricating the custom curved framing to create the exact shapes Gehry wanted.

Using 3D modeling, curved studs, curved box beams, curved channel, and knife edges were designed to meet the design intent and acoustic requirements. During this stage, there was also analysis with adjacent systems for clash detection and fit informed the design solution. The entire framing system was coordinated with audiovisual (AV), air-conditioning (AC), and lighting systems to fit seamlessly.

The CFS framing’s 3D model provided the data to fabricate 46,975 m2 (505,638 sf) of material, which included 3432 curved studs, and 2632 curved track framing pieces. Ninety four percent of the materials were created uniquely for the project. The company even developed a proprietary new construction method—knife edges—for corners that were not at right angles (a condition common in Gehry’s design). Every detail was designed with the project’s ultimate goal in mind: marvelous acoustics.

An evening view of the New World Center, featuring The Wall (a 650-m2 [7000-sf] projection wall) and SoundScape (a 1-ha [2.5-acre] multiuse urban space).

An evening view of the New World Center, featuring The Wall (a 650-m2 [7000-sf] projection wall) and SoundScape (a 1-ha [2.5-acre] multiuse urban space).

A view of the Atrium through New World Center’s six-story window wall where abstract forms and curved surfaces above house practice rooms for musicians and offi ces for the venue.

A view of the Atrium through New World Center’s six-story window wall where abstract forms and curved surfaces above house practice rooms for musicians and offices for the venue.

The New World Center’s main performance hall delivers a multimedia experience with crisp acoustic integrity.

The New World Center’s main
performance hall delivers a
multimedia experience with
crisp acoustic integrity.

 

 

 

 

 

 

 

 

 

 


Conclusion

Streamlining the construction process from blueprint to acoustic plaster element or complex ceiling design is achieved with advanced building information modeling (BIM), 3D modeling, CFS fabrication, and framing technology. This combination opens up unlimited acoustical opportunities for performance spaces around the world.

No longer are designers limited by straight lines and right angles. Curved surfaces can bring new levels of acoustic perfection to a space and can be precisely designed and studied prior to construction, as acousticians add subject matter experts like cold-formed steel framing manufacturers (and their tools) to the project team. The results, as patrons of both Kauffman Center for the Performing Arts and New World Center will attest, can be pitch-perfect.

Chuck Mears, FAIA, is the chief design officer and founder of Radius Track Corporation. He is an expert in the design and fabrication of complex cold-formed steel framing. Mears’ work in 3D computer modeling and fabrication technology allows his team to create cold-formed steel structural systems to support any imaginable architectural form. He can be contacted at chuck@radiustrack.com.

Choosing a Rubber Floor for Aesthetics and Performance

Photos courtesy Regupol America

Photos courtesy Regupol America

by John P. Aten

Functionality is the ultimate goal for athletic flooring, and high-performance assemblies can provide durability, shock absorption, acoustics, and aesthetics. Specifiers and designers should explore the various options based on individual projects.

Designers, architects, and specifiers have many questions to ask themselves before selecting facility floors. These include:

  • How much of the project’s budget can be dedicated to flooring costs?
  • Is sustainability an important factor?
  • Is the project new construction or a refurbishment?
  • What are the primary and secondary uses—is it a single-use or multi-purpose floor?
  • According to its use, what are the key athletic floors properties (e.g. shock absorption, energy return [i.e. the energy returned to the athlete after impact], floor deformation, or ball rebound)?
  • What are the aesthetic goals for the space? Is it an ideal location to promote brand recognition?

Now produced from recycled tires, rubber flooring is a high-performance, sustainable material that is often specified for athletic facility floors. The recycled tires are ground with color chips before being combined with a bonding agent. With color consistent throughout the product, the top does not show wear like products with a veneer or thin wear layer.

Before the 1990s, earlier similar products had a strong odor and lacked aesthetic options. Now, recycled rubber is customizable, and meets current South Coast Air Quality Management District’s (SCAQMD) volatile organic compounds (VOC) and indoor air quality (IAQ) standards.

Benefits of rubber flooring

Consisting of 100 percent post-consumer recycled tire rubber, the 25-mm (1-in.) thick flooring at Iowa State University’s facility provides superior performance and durability for the weight room.

Consisting of 100 percent post-consumer recycled tire rubber, the 25-mm (1-in.) thick flooring at Iowa State University’s facility provides superior performance and durability for the weight room.

In addition to a long service life, recycled rubber flooring requires low maintenance of routine damp mopping with neutral pH detergent. Roll and sheet products can be made with a smooth bottom and molded tiles can be manufactured with a waffle bottom to provide optimal shock-absorption for space such as cardio or heavy free-weight areas.

The void created by the waffle bottom adds a level of air-cushioning to the surface. The material’s density, along with the spring surface, is able to compress and then have a cushioning effect. The extra-thick, unique composite structure also provides durability.

Logos and custom color blends allow facilities to incorporate design and even targeted marketing. Produced using high-quality manufacturing standards, the rubber withstand a lot of abuse without losing performance capabilities. Customizable recycled rubber, made of 100 percent post-consumer content, offers aesthetic flexibility. Colleges will often employ team logos and school colors while athletic clubs can display their brand identity. Prefabricated for precision in density, thickness, and physical properties, its modular possibilities provide a range of functions as well as flexibility for various spaces.

For specifiers, recycled rubber flooring is an excellent choice for various areas of a facility. With the manufacturing easily producing both small and large batches, recycled rubber can be specified to fit a small locker room or a large arena.

Recycled rubber flooring uses 100 percent post-consumer tire rubber and post-industrial ethylene propylene diene monomer (EPDM) rubber in its manufacturing.

Flooring specification begins with determining the area’s function. From multi-purpose areas to single-use spaces, performance—including such factors as the level of shock absorption, durability, maintenance, acoustics, aesthetics, and sustainability—is all decided by the desired function. Specifiers must also consider the wear and tear of the space, and choose a surface that provides the best biomechanics to minimize athletic injuries.

For all types of flooring, installation requires an understanding of various factors, including moisture prevention and vapor emissions. Prior to installation, thorough testing of the area must be done to ensure adhesives can properly bond the flooring to the concrete, which will minimize maintenance problems in the future. This testing can be done during the installation and should be conducted by the flooring contractor as certain products have different moisture and relative humidity (RH) specifications.

Strategically designed with a waffle bottom, this floor provides shock-absorption, drainage, and cable routing. Its thick, composite structure is durable with wear resistance.

Strategically designed with a waffle bottom, this floor provides shock-absorption, drainage, and cable routing. Its thick, composite structure is durable with wear resistance.

Sustainability and environmental concerns are becoming a standard part of the specification process. In a large space like a sports facility, this becomes even more important. When maintaining a healthy environment, product’s volatile organic compounds (VOCs) and indoor air quality (IAQ) should be considered. For example, California has the strictest indoor air quality regulations for adhesives and building materials and products are third-party-tested to meet the state’s standards.

By having the products third-party verified, certain emission levels are tested based on organic compounds and formaldehyde, and levels cannot be higher than the threshold. (Throughout the United States, most manufacturers aim to meet California levels.) Though their initial costs may be slightly higher than low cost floor alternatives, the benefits of choosing a product such as recycled rubber flooring are ten-fold.

Measuring the benefits

While it can be difficult to measure the benefits of each type of high-performance flooring, responsibly designed flooring can minimize sports injuries through shock absorption and provide a more enjoyable experience. If the floor is selected based on its intended use, relevant testing data can provide background on how it fits the project. Standardization of safety rulings can aid specifiers in choosing the right surface. Specific sports flooring testing methods are employed to guarantee requirements are met.

There are certain safety requirements everyone must abide by, but some of the test methods are specific to the facility. For example, some are looking for pure performance or aesthetics. Every owner comes to a project with a certain criteria, but tweaks the specifications to fit their facility.

ASTM F2772-11, Standard Specification for Athletic Performance Properties of Indoor Sports Floor Systems, measures various performance characteristics for building products. Flooring is evaluated on four criteria:

  • force reduction;
  • ball rebound;
  • vertical deflection; and
  • surface finish effect.

It is then classified into one of five performance levels. In order to meet the standards of ASTM F2772-11, a floor must maintain:

  • 10 percent minimum shock absorption;
  • less than 3.5 mm (0.13 in.) vertical deformation;
  • minimum 90 percent ball rebound; and
  • between eight and 110 sliding effect value.

A plethora of options
Within the key sports flooring categories—namely vinyl, rubber, wood, and polyurethane—there are many divisions and price points. By knowing the intended use of the floor, specifiers can determine the ideal material based on the benefits.

CS_March_2014.inddDepending on whether this is a new project or refurbishment also plays a role in the appropriate selection. Modular rubber flooring works well for refurbished projects because a lot of floor preparation is not required. It can be laid right over top the current underlayment while other adhered options may require more preparation.

Aside from rubber, vinyl flooring is also a resilient surface, offering performance and design. In fact, vinyl includes the option to be printed as ‘wood grain.’ Cost and other benefits have solidified vinyl’s place in the athletic flooring world and the material is often selected for multi-purpose courts, institutional centers, gyms, and yoga studios.

A great option for hard and cushioned surfaces, rubber flooring comes in virgin sheet rubber and recycled rubber, which negotiates issues of sustainability and cost. Virgin sheet rubber has one of the highest price points, but also offers high performance, durability, and aesthetics.

Given the total cost of ownership, recycled rubber flooring as there are many options available based on use.. For example, in a weight room it is now a realistic option to use recycled rubber flooring. The benefits of employing rubber over carpeting include cleanliness in areas with heavy use. Instead of needing frequent, heavy-duty carpet cleaning, building owners can specify recycled rubber and know their upkeep costs will be lowered.

For a hard surface, wood flooring is a traditional choice, but its challenges include high maintenance costs and less flexibility. Wood flooring is specified by grade, thickness, and width.

Aesthetics and acoustics

Branding, team spirit, and loyalty are paramount in sporting facilities, and athletic directors and facility managers are looking to incorporate team logos and colors into the design. The hard surface of vinyl offers many possibilities, from painting to special printed effects. As discussed earlier, recycled rubber also has many customization and color options, ranging from standard black to numerous vibrant color blends in varying intensity to add color and visual effect.

Franklin & Marshall College (Lancaster, Pennsylvania) employed athletic rubber flooring for its high performance.

Franklin & Marshall College (Lancaster, Pennsylvania) employed athletic rubber flooring for its high performance.

Acoustics are another concern for areas with heavy use. Vinyl and wood do little to filter sound. Recycled rubber, however, is a material that cuts acoustic output and produces a less noisy space. For areas that require quiet, recycled rubber is a great fit.

Noise absorption is achieved by minimizing vibrations from sound. Facilities with multiple levels benefit from reduced sound from upstairs. Impact noise (i.e. when something is dropped on the floor) produces energy resulting in loud disruptions as it vibrates through the floor assembly.

As rubber flooring is not completely a hard surface, the sound is absorbed. Citing the noise reduction coefficient (NRC) can prove the effectiveness of acoustical airborne sound control, and rubber flooring can also reduce the impact sound through transmission to another floor below, also known as impact insulation class (IIC).

Conclusion

For sports and athletic flooring, functionality is understandably the goal. Recycled rubber, suitable for many types of areas, is an excellent choice for all areas of an athletic facility, from cardio areas, weight rooms, spinning rooms, to entryways and corridors. High performance—defined by a great showing in the level of shock absorption, durability, maintenance, acoustics, aesthetics, and sustainability—can be attained by thoroughly knowing the options available.

John P. Aten is the vice-president of sales and marketing for Regupol America. He has spent 23 years in the floor covering business, with an emphasis on the sports and fitness segments. Aten’s experience ranges from installing tracks to working closely on the specification of products for Big Ten athletic facilities. He can be reached at jpa@regupol.com.

A Sound Decision

Wood brings acoustic value to structures
by Michael Heeney

In the sea of concrete and granite that people have come to expect from buildings in Washington, D.C., one structure showcasing wood stands out from the crowd. When Arena Stage at the Mead Center for American Theater reopened in 2010, it was the capital’s first modern structure of its size to use heavy timber components. It was also the country’s first project to use a hybrid wood and glass enclosure to envelop two existing structures. Designed by Bing Thom Architects (with Fast+Epp Structural Engineers, Clark Construction, and StructureCraft Builders Inc.), the structure has a lobby large enough to hold up to 1400 patrons from all three theaters out at the same time. To warm that huge space and absorb sound, the design team again used stained poplar for the wood soffit on the lobby ceiling.
Photos © Nic Lehoux. Photos courtesy Bing Thom Architects

When designing a commercial structure, it is important to consider the situational aspects and parameters before selecting the most appropriate building products. While limitations such as budget and availability often sit at the forefront of these decisions, factors like aesthetic details and desired outcomes must be taken into account. One of the chief considerations for many projects should be the acoustics, encompassing everything from sound transmission to absorption and reverberation. Continue reading