Cavity Shaftwall: What You Need to Know
OnBoard Newsletter | December 2023
Cavity shaftwalls are crucial for ensuring the safety of occupants in multi-story commercial buildings, as they protect the means of egress. Even before the construction of the World Trade Center began in 1966, gypsum board manufacturers were developing an alternative to the traditional masonry elevator enclosures for this tall skyscraper. The solution they came up with was the cavity shaftwall system.
What is a Cavity Shaftwall System?
A cavity shaftwall is a non-load-bearing, 1- through 4-hour, fire-rated partition constructed from one side and used to enclose elevator shafts, stairs and mechanical shafts where the design requires resistance to fire. These systems can also be used as fire-rated, interior partitions where access is restricted to one side and as fire-rated, horizontal membranes.
Shaftwalls are fire rated from both sides of the wall, so they can be installed in either direction. They’re ideal when contractors can’t access one side, such as adding a fire-rated wall next to an existing wall.
Benefits Over Conventional Masonry
Shaftwalls are four to five times lighter and considerably less expensive to install than traditional masonry enclosures. With access challenges in taller buildings, constructing cavity shaftwalls from only one side makes installation easier.
Q: Are shaftwalls fire-rated from both sides?
A: Yes, they are tested from fire exposure on both sides of the assembly.
Q: Can I install shaftwalls in either direction?
A: Yes, you can install them in either direction since they are fire-rated from both sides.
Q: What determines the required fire rating of a shaft enclosure?
A: Shafts serving three stories or less require a 1-hour fire rating. Shafts serving four stories or more require a 2-hour fire rating.
Q: How do I make repairs on shaftwalls?
A: Whether it’s a small or large hole, reference pages 92-95 in The PURPLE Book® for repair details on 1- and 2-hour fire-rated shaftwalls.
Q: Can I use shaftwall assemblies as ceilings in corridors?
A: Because they can be built from below, shaftwalls are commonly used as ceilings in fire-rated corridors. To view a 2-hour shaftwall assembly used as a lid or ceiling on a 2-hour corridor, reference page 105 of The PURPLE Book. For shaftwall ceilings other than corridors, reference page 97.
Q: When must shaftwalls provide impact resistance?
A: As a result of the September 11 attack on the World Trade Center, International Building Code (IBC) high-rise buildings of Risk Category III or IV (schools and hospitals, for example) and all buildings over 420’ must meet the following levels of impact resistance as defined by ASTM C1629: Standard Classification for Abuse-Resistant Nondecorated Interior Gypsum Panel Products and Fiber-Reinforced Cement Panels:
- Soft-body requirements of Level 2.
- Hard-body requirements: The exterior face of the shaft enclosure must include either two layers of gypsum board with each meeting Hard-body Level 2 or one layer of gypsum board meeting Hard-body Level 2 or multiple layers tested together meeting Hard-body Level 3.
- Note: To meet both the soft- and hard-body impact requirements of the IBC, install Gold Bond® XP® Hi-Impact® Gypsum Board as the face layer on the tenant side of a 2-hour shaftwall.
For more FAQs, please visit this NGC Blog post.
Key Components for Shaftwalls
Shaftliner, J-track and shaftwall studs are a few key components in shaftwalls. Use 1” thick by 24” wide gypsum panels on the shaft side of the shaftwall assemblies. Gold Bond® Shaftliner XP® and Gold Bond® eXP® Shaftliner can create 1- and 2-hour UL fire-rated shaftwall assemblies. J-track is metal track shaped like the letter “J” with uneven flanges at the top, bottom and ends of a shaftwall assembly. Shaftwall studs are CT, CH or I shaped steel studs designed to be friction fit into the J-tracks of a shaftwall assembly with integral slots and tabs to support the shaftliner panels.
Shaftwall System Resources
Understanding Shaftwall Design - Get answers to 10 common questions about shaftwall and stairwell enclosures for commercial buildings. Learn more.
Cavity Shaftwall System Details - Reference pages 183-195 in the NGC Construction Guide™ for an overview of construction and technical details. To find a shaftwall enclosure assembly detail that best meets your project requirements, refer to pages 50-95 of The PURPLE Book. Specify UL Design No. W419 for your 1- to 4-hour cavity shaftwall systems.
How to Build a Shaftwall in Commercial Construction - Learn the details of building a shaftwall system from the experts at 1-800-NATIONAL®, including details for corners, duct and elevator door openings.
“The PURPLE Book dedicates 45 pages to shaftwall construction. Each one of your projects is unique and may require a detail that isn’t straightforward. Reach out to your local construction design manager for help. We have the resources to keep your project moving forward.”
Scott HughesConstruction Design ManagerNational Gypsum Company
"Designers today have more flexibility in both cavity shaftwall material selection and system design. Modern shafts may be enclosed with cast-in-place concrete, masonry, gypsum plaster, steel stud drywall or specially designed gypsum panel shaftwall systems. National Gypsum has a great selection of UL designs to help in your building design."
Alan ZeedykConstruction Design ManagerNational Gypsum Company
Product Spotlight: Cavity Shaftwall Product List
We recommend these Gold Bond products to construct cavity shaftwalls. They all have built-in mold-, mildew- and moisture resistance and have achieved UL GREENGUARD Gold certification for optimal indoor air quality. Consider specifying:
This November, ProForm Finishing Products began shipping a more environmentally friendly pail, including 30% post-consumer recycled (PCR) plastic, from its Belcamp, MD plant. This packaging transition will expand to all ProForm manufacturing plants in 2024.
By reducing the environmental impact of ProForm packaging, we support the circular economy for plastics recycling while maintaining the same high-performance finishing product. Learn more!
New Course Under Construction - We are developing a cavity shaftwall systems course that will launch in 2024. Contact your construction design manager in advance to book this LIVE Lunch ‘N Learn.
Continuing Education - It’s time to plan your continuing education for 2024. Expand your knowledge and skills with our wide array of in-person and online continuing education courses, all of which are eligible for AIA learning credits. Contact your construction design manager today to schedule a Lunch ‘N Learn that will provoke thought and stimulate discussion.
From expertise on building products in fire- and sound-rated assemblies to specifying the best products for your next project, we have a construction design manager available to provide architectural design assistance every step of the way. We are here to help you design and build better. Connect now!