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By: Robert Grupe
Director, Architectural and Technical Solutions, United States Gypsum Company

Phil Shaeffer
Manager, Codes and Technical Support, United States Gypsum Company

Dean Updegrove
Product Marketing Manager, United States Gypsum Company

5. To provide the safest possible cavity shaft wall construction, carefully review the manufacturer’s limiting height data.

6. Oscillating height testing is another key consideration. Manufacturer oscillation testing has demonstrated that J-runners at the top and bottom of the shaft wall should be at least 24 gauge to withstand the positive and negative pressures created by the elevators. Lesser-strength J-runners can fatigue and may be subject to fastener failure and fracturing. Look for specific test data up to at least 1 million cycles to ensure overall system longevity.

7. When designing mechanical shaft walls, give careful consideration to ductwork penetrations. If not designed properly, these penetrations may negate the wall’s fire endurance rating. Typically, a fire damper in the ductwork itself is sufficient; however, make sure the damper is compatible with the type of wall specified and that both the wall and the damper have been evaluated under actual fire testing.

8. Typically, shaft wall installation closely follows the erection of the superstructure. This is done to provide a safety barrier around the shaft openings and speed the installation. Unfortunately this is sometimes done prior to completion of the exterior envelope. This exposes all building materials to moisture, which can lead to a variety of adverse conditions. To ensure proper performance, it is vitally important to control moisture on a project. (More information on moisture control is included in the required additional reading materials.)

9. Shaft walls with elevator door frames in them should be a minimum of 5 inches thick to accommodate the boxes for call buttons, position indicators and fireman’s access keys.

10. Where shaft walls enclose elevator and unlined return air vents, and intermittent pressures are expected, sealant is recommended at intersections with floors, ceilings, columns, ducts, etc. to seal peripheries and penetrations to minimize whistling and dirt accumulation due to air movement.

11. If the gypsum shaft wall is intended to enclose a mechanical shaft and there will be no sheet metal ductwork, the system should be designed with the following performance provisions:

• The gypsum board surface temperature should not exceed 125 degrees F.
• Air stream dew point temperatures should be maintained below gypsum board surface temperatures.
• The assembly should be designed to withstand sustained design uniform air pressure loads not exceeding 10 psf. Start-up surges should be no greater than 11/2 times the design static load.
• Separate approved liners should be installed in areas subject to continuous moisture overspray, condensation or air stream temperature exceeding 125 degrees F.
• Appropriate sealants should be used to ensure airtight construction.

Conclusion

Because gypsum shaft walls enable designers to meet all key performance, design and installation criteria more effectively than competing systems, they are now considered the standard for low-, mid- and high-rise construction. Gypsum systems not only enabled the construction of ultra-high-rise buildings such as the Sears Tower in Chicago and the Petronis Towers in Kuala Lumpur, Malaysia, but they also provide a superior combination of benefits for low- and mid-rise construction.

No matter what the application, gypsum shaft walls are required to meet a complex range of performance and design functions. As such, architects must account for multiple variables in the specification process. With this in mind, designers are well advised to work with manufacturers that offer the most extensive testing data and technical support services. Doing so will minimize the risk for all parties involved and ensure long-term performance.

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