Volume 26, Issue 3 - May/June 2012

Glass Tech

Walking on Air
Transparent Floors and Stairs Make Dreams Come True

by Ashley M. Charest

Have you ever had one of those dreams where you’re between floating and walking on your own, seeing everything below you confidently, and yet lightly walking with small unsure steps? We’ve all had that dream. Technologies today have made that floating-on-air sensation possible through the design and installation of glass floors and stairs. Walking on a glass floor is much like your dream. It’s very cool, and you are still aware that you can see straight down.

The Glass Association of North America (GANA) has an informative Glass Informational Bulletin on this subject. The below text is taken directly from LD 06-1107 Glass Floors and Stairs and the full document can be downloaded at

Choosing the Glazing
Several types of glass products are used in floors and stair treads, including laminated glass and glass block systems. A description of these glass types follows:
• Laminated glass - two or more pieces of glass bonded together with an interlayer. The glass may be annealed, heat- or chemically-strengthened or fully tempered.
• Glass block - a decorative hollow glass building block that is set in an aluminum or concrete framework and sealed against moisture.

Providing Slip Resistance
Slip resistance of a walking surface is an important safety consideration. The Occupational Safety and Health Administration requires a minimum slip resistance, expressed as a static coefficient of friction of 0.50. However, special activities, such as dancing, may require a different level of slip resistance. Glass floors used near entrances that may get wet require special consideration.

There are a variety of ASTM test methods that measure slip resistance using specific test equipment under dry or wet conditions. These are:
• F 609 - Standard Test Method for Static Slip Resistance of Footwear, Sole, Heel, or Related Materials by Horizontal Pull Slipmeter (HPS);
• F 1677 - Standard Test Method for Using a Portable Inclinable Articulated Strut Tester (PIAST);
• F 1679 - Standard Test Method for Using a Variable Incidence Tribometer (VIT); and
• D 2047 - Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine.

Other industry standards, such as ASTM F 1637 - Standard Practice for Safe Walking Surfaces, ASTM F 1646 - Standard Terminology Relating to Safety and Traction for Footwear and Underwriters Laboratory4 (UL) UL 410 - Slip Resistance of Floor Surface Materials, address the safety issues of walkway surfaces from a more general point of view.

Processes designed to roughen the top surface of the glass to provide slip resistance include sandblasting, acid-etching, ceramic frit and embossing. It is important to note that sandblasting may reduce the strength of the glass by as much as 50 percent. Therefore glass flooring should never be sand blasted in the field without a complete engineering analysis.

Considering Modesty
Modesty becomes an issue when glass floors are found on upper levels and inappropriate lines of sight are created from spaces below. When modesty is a concern, it may be necessary to incorporate a ceramic enamel finish or a decorated or translucent interlayer in the glass to create opacity.

Glass floors can be tested for strength or impact resistance. Test methods that are used include:
• ASTM E 72 - Standard Test Methods of Conducting Strength Tests of Panels for Building Construction;
• ASTM E 695 - Standard Method for Measuring Relative Resistance of Wall, Floor, and Roof Construction to Impact Loading; and • ASTM E 2322 - Standard Test Method for Conducting Traverse and Concentrated Tests on Panels Used in Floor and Roof Construction.

Additional resources include UL 410 Slip Resistance of Floor Surface Materials and the American Disabilities Act for information on friction rating and route requirement criteria.

Ashley M. Charest is the account executive for the Glass Association of North America in Topeka, Kan.


Architects' Guide to Glass & Metal
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