Structural Silicone Glazing Changing the face of architectural design

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Perhaps no other city in the United States can point to a more modern skyline than Dallas. Certainly no other city relies more on structural silicone glazing to bring distinction to its urban landscape. From Lincoln Plaza to One Spectrum Center to the Allied Bank Center and more, the list of buildings structurally glazed with Dow Corning® brand silicone adhesive/sealants is long. The design diversity is amazing. The effect is remarkable.

©1990, 1999 Dow Corning Corporation. All rights reserved.

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NOTE: Photography in this brochure shows applications for Dow Corning ® brand silicone construction materials. Endorsements of specific products are not implied unless specifically stated.

Transforming urban skylines Structural silicone glazing is one of the most versatile forms of curtainwall construction in the commercial facade business. In the past three decades, it has helped architects and designers transform the skylines of cities around the world. Dow Corning Corporation has contributed to the technology’s advancement and the success of those who have employed it since the beginning. Dow Corning, the world leader in silicone technology, was a key contributor in America’s first multi-story structural silicone glazing project in 1971, working in concert with the architects and curtainwall manufacturers and creating the first adhesive/sealants to be used as the primary curtainwall attachment. Since that first project, architects and builders have relied upon Dow Corning for virtually every new advancement in the technology, producing ever-increasing design freedom, performance, long-term savings and durability.

Design freedom Structural silicone glazing gives architects and designers the freedom to create dramatic facades. This effective and economical technology allows architects to adhere glass, ceramic, metal, stone and composite panels to building frames using silicone adhesive/sealants. Its design potential to enhance the aesthetic appeal of commercial buildings is almost unlimited. For both new construction and renovation projects, structural silicone glazing is proven technology that produces striking results.

Structural silicone glazing allows architects to create some of the world’s most unique and beautiful buildings. In 1994, Hellmuth, Obata & Kassabaum, P.C., specified silicone adhesive/ sealants from Dow Corning for structural glazing of the dazzling porcelain tile facade of the new

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United States Navy Intelligence Center building in Suitland, Maryland.

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In 1983, Park Avenue Tower was New York City’s first experiment with structural silicone glazing. With over 220,000 square feet of reflective glass curtainwall adhered with an adhesive/sealant from Dow Corning in a two-sided structural glazing system, the 37-story office tower immediately became a landmark for its soaring, delicate beauty. It also became the standard by which the dozens of structural silicone glazed buildings that followed were judged.

Performance Beauty is only skin deep. It’s important for a building to be aesthetically appealing, but it’s also critical that the building be structurally sound. The key to successful structural silicone glazing is a highperformance silicone adhesive/sealant, formulated and tested to meet the demanding performance requirements of this curtainwall technology.

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In a structural silicone glazing system, the silicone sealant serves a dual purpose. It seals the building from the elements and supports the building’s curtainwall, transmitting wind loads to the structure. When properly designed, specified and fabricated, the system withstands flexure, tension, compression, thermal shear stresses and continuous movement. It also stands up to weathering, extreme temperature changes and chemical corrosion. Silicone sealants form watertight bonds, adhere through weather extremes, withstand designer-specified joint movements and remain flexible. Silicone is the only sealant alternative to mechanical fastening. That’s because silicone sealants are the only sealants with the stability, adhesion and movement capability required to withstand the rigors of structural glazing applications.

Long-term savings In addition to greater design freedom and reliable performance, structural silicone glazing offers economic advantages. Structural silicone glazing technology promotes optimum sound and heat insulation. Moreover, the elimination of thermal breaks and unnecessary metal can further reduce building costs. Properly installed, four-sided structural silicone glazing systems provide leak-free performance. This is because the silicone sealant, used as an adhesive by design, also seals out air and water – and with certain designs can eliminate weep systems.

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Photo courtesy of HNTB Architects, Engineers, Planners. Photographer: Mike Sinclair

In 1985, the architectural firm of Howard, Needles, Tammen & Bergdoff designed an office tower that fit perfectly into Kansas City’s downtown of traditional stone buildings. The 38-story Town Pavilion features vertical granite bands on each side of the building, flanked by contemporary reflective glass curtainwall. The structure uses both two- and four-sided structural silicone glazing with Dow Corning adhesive/sealants for structural glazing and weathersealing. The Town Pavilion is reminiscent of the past, yet unmistakably modern – proof of the design potential of structural silicone glazing.

Reliability With literally thousands of buildings worldwide constructed using structural silicone glazing in the past three decades, the technology has earned a well-deserved reputation for reliability. This track record has been built by the cooperative efforts of architects, consultants, designers, structural engineers, curtainwall manufacturers and erectors, and glass and component suppliers that help ensure successful structural silicone glazing designs. Dow Corning strongly recom-

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mends this complete cooperation

When California’s worst earthquake since 1906 struck the San Francisco area in 1989, structural silicone glazing passed the test at the Marathon Plaza, the city’s largest concrete commercial building. While neighboring buildings had windows crack and fall out, and the nearby Embarcadero Freeway suffered massive damage, the Marathon Plaza’s two-sided structural glazed ribbon windows “floated” on their silicone sealant from Dow Corning, cushioned against the

throughout all phases of project planning and construction. Materials used in structural silicone glazing must be matched for adhesive properties, compatibility and proper dimensions. Therefore, careful pre-job testing, design,

seismic movement. Not a single lite was lost.

material selection and close

control of workmanship contribute to the reliability of this system. That’s why a prior review by Dow Corning is required for each structural application project before a warranty is issued. This review process helps

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ensure that the proper steps are taken to a successful project completion.

The Atria West office building on Los Angeles’ Santa Monica Boulevard features five soaring 50-foot atria and 900 feet of glass curtainwall in a two-sided structural glazing system with vertical mullions. When a severe earthquake jolted the Los Angeles area in 1994, none of its hundreds of glass lites

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were cracked or lost. Though just 15 miles from the epicenter, Atria West shrugged off the quake and more than 6,000 aftershocks and went on with its business

5 Photo courtesy of The Nadel Partnership, Inc.

A design primer There are two basic forms of structural silicone glazing: two-sided and four-sided. Both can be fabricated by being either (1) glazed in the factory (shop-glazed) or (2) glazed directly on the job site (field-glazed). In general, shop-glazed elements can be fabricated under more easily controlled conditions – eliminating exposure to airborne dust and debris, and ensuring maximum cleanliness, sealant cure and development of adhesive properties. These elements are then moved to the job site and mechanically attached to the curtainwall structure. Two-sided structural silicone glazing provides mechanical support for either vertical or horizontal joints (see Figure 1). In this illustration, only the vertical joints are structurally adhered to the supporting structure. The dead load of the panel weight is supported mechanically. The live load is carried on two sides by structural silicone adhesive/sealant, and is carried at the head and sill by mechanical fastening. Four-sided structural silicone glazing provides no mechanical support for the facade-fronting materials (see Figure 2). Silicone adhesive/sealant is used for glazing on all four sides. Dead loads are either supported mechanically by a horizontal fin or by the silicone sealant, depending upon the design. Four-sided structural silicone glazing systems are also less likely to leak due to the adhesive/sealant, which blocks water and air

Figure 1. Two-sided structural silicone glazing

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from entering the building interior. This design may incorporate a split mullion that acts as an expansion joint, thereby simplifying the building design. Structural silicone glazing can also incorporate insulating glass units (see Figure 3). A horizontal fin is used to support the weight (dead load) of the insulating glass unit. These insulating glass units must also be sealed with silicone sealant. Very heavy stone panels may also require additonal dead-load support.

Figure 2. Four-sided structural silicone glazing

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Figure 3. Design system for insulating glass units 1

1. Insulating glass unit 2. Structural silicone glazing sealant 3. Silicone rubber spacer 4. Silicone rubber setting blocks 5. Aluminum support 2

6. Backer rod 7. Width of SSG joint 8. Depth of SSG joint

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9. Width of weatherseal 10. Silicone weatherseal 11. Silicone insulating glass sealant

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For each design project, the dimensions of the structural and weatherseal joints are calculated individually. Special considerations must also be made in the design of the insulating glass unit (see Figures 4 and 5).

Figure 5. Typical structural glazing design Structural Glazing Design Guidelines 1. Glue thickness must not be less than 1/4". 2. Structural bite must not be less than glue thickness. 3. Structural bite (in) = 0.5 x smallest leg of largest lite (ft) x windload (lb/ft2) Sealant design strength* (20 lb/in2) x (12 in/ft) 4. Always round up when using the above equation. For instance, a 4' x 8' lite under a 40 psf windload requires 0.3333" of silicone. This is then rounded up to 3/8". Never round down.

Figure 4. Sealant bite for windload on rectangular glass panels

5. The structural sealant joint must be able to be filled using standard caulking practices.

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6. The structural joint must not move during cure.

Smallest Glass Dimension (ft)

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These are only preliminary guidelines for structural glazing details. 10

Dow Corning must review all structural glazing details before any warranty can be issued.

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GLASS

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Windload (psf) SILICONE STRUCTURAL ADHESIVE

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*Dow Corning structural glazing sealants have a minimum ultimate strength of 50 psi. We recommend a 2.5:1 safety factor, resulting in a 20 psi design strength.

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A commitment to quality and service Dow Corning is committed to ensuring the quality and high performance of its silicone construction materials. Dow Corning offers a Structural Glazing Sealant Warranty for construction projects in the United States and Canada. This warranty certifies that Dow Corning silicone construction sealants will not fail adhesively or cohesively for a period of 20 years from the date of purchase, when used in accordance with Dow Corning recommendations. To qualify for the warranty, actual project job site substrates, blueprints and design specifications must be submitted to Dow Corning for review and testing. Job site substrate samples must include glass or panels, mullions and other elastomeric spacer and gasket materials that may come in contact with Dow Corning silicone construction sealants. These materials are then tested for compatibility and for their effect on the adhesive properties of the structural silicone sealant under accelerated performance testing conditions. Dow Corning’s print/specification assessment is performed to review the sufficiency of the joint designs to provide proper adhesion in accordance with the specified types and sizes of materials and the windload specifications. These tests are also conducted to ensure optimum performance of the Dow Corning silicone construction sealants selected for your specific construction project. Warranty requests may be submitted through your Dow Corning sales representative, regional construction project service testing facility or your local Dow Corning distributor. AV04464

Specific warranty details and limitations are outlined in the Dow Corning Structural Silicone Glazing Warranty. This warranty program currently applies only to construction projects in the United States and Canada. However, other Dow Corning regions may offer similar

Around the world, Dow Corning people provide the project coordination experience and technical expertise to help the most challenging construction and renovation projects succeed.

programs. For additional information on international projects, please contact the Dow Corning Corporation office in the area in which you are doing business. (See back cover.) For answers to technical questions, call Dow Corning Customer Service at (517) 496-6000.

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Global project service and support Three decades of experience helping customers successfully construct structural silicone glazed buildings or renovate older buildings using the technology has enabled Dow Corning to develop specialized tests and project services. These are available at regionally located facilities in the United States, Australia, Belgium, Brazil, Japan, Germany and the United Kingdom. Dow Corning also maintains extensive records on substrates and accessory

Quality products are only part of the equation. Dow Corning is committed to providing its construction industry customers

components for pre-job material selection. Our laboratories provide preliminary print assistance with mock-ups and on-site inspec-

worldwide with the service and expert technical support they need to see projects from concept to

tions. Dow Corning has a worldwide network

successful completion.

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reviews, substrate and material testing and

of technical service centers and the industry specialists to provide support on a regional and global basis, ensuring rapid response to all your needs and hands-on assistance from the onset to the completion of your structural silicone glazing project. Structural silicone glazing provides architects and designers with remarkable creative freedom – made possible with Dow Corning silicone

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construction materials and Dow Corning’s commitment to your success.

Two old brick buildings in downtown Grand Rapids, Michigan, had little to recommend them in 1985, except an owner with vision. Striking new painted steel and glass facades, connected

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by a soaring atrium, turned the buildings into the award-winning 50 Monroe Place, proof of the value of structural silicone glazing in renovation projects. With a Dow Corning adhesive/ sealant sealing the vertical edges of the glass in this two-sided structurally glazed project, the old buildings have decades of renewed life and service ahead of them.

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Tampa’s modern skyline is proof of its vitality. The C&S Tower, 100 North Tampa Building and Mack Center II are just three of its landmarks

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that testify to the design versatility of structural silicone glazing and the quality and durability of silicone sealants from Dow Corning.

The Gateway Towers, Pacific First Center and 2nd & Seneca Building are among the many commercial buildings on Seattle’s dramatic skyline that rely on silicone adhesive/sealants from Dow Corning. Famous for its almost perpetual wet weather, but less well known as an active seismic zone, Seattle is a proving ground for the quality and performance of silicones.

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For more information Product information is available 24 hours a day, seven days a week, through our Select-A-Fax system. For an index of literature that can be obtained through the system, call 1-800-443-2932 or (516) 822-7650 on your touch-tone phone. Follow the prompts and enter 15 when asked for the Literature Code you desire. For information on specific Dow Corning silicone construction materials, enter the appropriate Literature Code(s) in the box below. AV04490

Within moments you will receive via fax the information you requested. Dow Corning maintains state-of-the-art materials testing laboratories around the

Select-A-FAX Literature Codes

world to help customers design and build with structural silicone glazed curtainwall technology.

Product ................................................... Literature Code Dow Corning ® 790 Silicone Building Sealant ............................. 618841 Dow Corning ® 791 Silicone Perimeter Sealant ........................... 621501 Dow Corning ® 795 Silicone Building Sealant ............................. 618851 Dow Corning ® 756 Silicone Building Sealant-H.P. ...................... 624721 Dow Corning ® 983 Glazing and Curtainwall Adhesive/Sealant .. 618641 Dow Corning ® FC Parking Structure Sealant .............................. 624891 Dow Corning ® NS Parking Structure Sealant .............................. 624871 Dow Corning ® SL Parking Structure Sealant .............................. 624881 Dow Corning ® 3-5000 Silicone Roof Coating .............................. 612711 Dow Corning ® 123 Silicone Seal .................................................. 624691 Dow Corning ® AllGuard Elastomeric Coating ............................ 620481

Contact Dow Corning For more information on Dow Corning silicone construction materials or the name of the Dow Corning sales representative or product distributor in your area, call: U.S. 1-800-322-8723

Belgium 32 2 655 2111

Singapore 65 253 6611

Canada 1-800-268-5359

Brazil 55 11 3759 4300

U.K. 44 932 351911

Mexico 525 327 1300

Hong Kong 852 5 215521

Australia

Japan

61 2 868 9111

81 3 3503 3561

Visit our web site at www.dowcorning.com.

We help you invent the future.™

WARRANTY INFORMATION – PLEASE READ CAREFULLY The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer’s tests to ensure that Dow Corning’s products are safe, effective, and fully satisfactory for the intended end use. Dow Corning’s sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment. Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted. Dow Corning specifically disclaims any other express or implied warranty of fitness for a particular purpose or merchantability. Unless Dow Corning provides you with a specific, duly signed endorsement of fitness for use, Dow Corning disclaims liability for any incidental or consequential damages. Suggestions of uses should not be taken as inducements to infringe any particular patent. Dow Corning is a registered trademark of Dow Corning Corporation. We help you invent the future is a trademark of Dow Corning Corporation. Printed in USA

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