Q: My project design requires that a continuous run of USG Cavity Shaft Wall be installed beyond the Limiting Height allowance listed in the SA926 brochure. What can I do to solve the problem?

A: For heights exceeding the Limiting Height tables found in the System Catalog (SA926) brochure, we recommend installing the 20 gauge x 6" C-H Stud in combination with a standard 4" C-Stud of heavier gauge. The two stud sections should be fastened together (back-to-back with fasteners spaced 12" o.c. and staggered. The design or project structural engineer must review any design. Q My project design requires a Shaft Wall system that will be installed to a continuous height of 70 feet. Is this possible with the USG Cavity Shaft Wall System?

Q: Can I substitute other products in these USG Cavity Shaft Wall assemblies?

A: No. The products indicated in the UL Design should be used to construct the USG Cavity Shaft Wall.

Q: Can I substitute components in a USG Cavity Shaft Wall?

A: Components other than those listed in the UL fire resistance design should not be used in a USG Cavity Shaft Wall. This could compromise the tested performance of the USG Cavity Shaft Wall.

Q: Can the Horizontal Shaft Wall carry live loads?

A: No. The ceiling is designed to carry only its own weight.

Q: What are the UL Design numbers for USG Cavity Shaft Wall?

A: UL Design Numbers U415, U438, U459, U467, U469, and U492.

Q: I have an air duct I need to enclose. Can I use USG Cavity Shaft Wall?

A: Yes! USG has a design for a 2-hour Cavity Shaft Wall enclosure.

Q: In SA926, I see limiting height tables for unlined shafts, as well as regular shafts. What is the difference?

A: The difference is in one case the load is considered intermittent, or the load is only applied as the elevator moves by. In the other case the load is sustained or constant. This would be the case for air handling systems. The sustained load is far more severe. The codes allow us to increase the allowable stress by 1/3 if the load is considered intermittent.

Q: I need to have a 2 hr. rated corridor ceiling. What can you offer?

A: USG Cavity Shaft Wall

Q: What sizes are available for USG C-H Stud?

A: 2 1/2", 4" and 6" 25, 22 and 20 gauge. Please contact your local USG Representative for pricing and availability.

Q: Can the Shaft Wall span be greater than what is published?

A: In order to achieve span heights greater than the limited spans the system must be tied back to the structure. The Architect or Engineer of Record determines the details for this attachment.

Q: In the SHEETROCK® Brand Shaft Wall System, can 5/8 inch Type X gypsum board, be substituted for 1/2 inch Type C gypsum board?

A: Yes

Q: Can the Horizontal Shaft Wall be penetrated for light fixtures?

A: No.

Q: Why is the USG J-Runner 24 ga.

A: Elevator shaft walls are considered working walls. By that, they flex both inward and outward as the elevator passes by. This flexing causes the runner track to fail due to fatigue. Tests have shown that to oscillate one million cycles the gauge of the runner has to be increased to 24.

Q: Are the Shaft Wall limiting heights, free spanning heights?

A: No. The heights are slab-to-slab spans.

Q: Is the Horizontal Shaft Wall UL tested?

A: No. The system has been tested for fire and is covered for use throughout the United States. The fire test number is WHI 495-PSH-0154/0167 and report number is NER-258 and ER-5693. UL, and rightly so, will not provide a number to system that falls outside the scope of ASTM testing. In this case, to meet the requirements of ASTM E119 testing, the system would be considered a floor ceiling assembly. As such it must be structurally designed to carry live and dead loads. Shaft Wall membranes cannot handle live loads. They can only cover dead loads. Also, in some cases the fire exposure on a membrane is from the top, which would never occur in a floor ceiling assembly.

Q: Who makes the steel components for USG Cavity Shaft Wall?

A: All steel framing components for USG Cavity Shaft Wall are made to precise USG Specifications. Depending on the market you are in, the product will be made at one of three manufacturing locations:

• Marino/Ware Industries, South Plainfield, NJ
• USG Medina, Medina, OH
• CEMCO, City of Industry, CA

Q: What are the components of USG Cavity Shaft Wall?

A: SHEETROCK^® Brand Gypsum Liner Panels & SHEETROCK^® Brand Gypsum Panels (FIRECODE, FIRECODE C, or ULTRACODE CORE. Please refer to the appropriate fire-resistance design for specific panel selection.  

Q: Where can USG Cavity Shaft Wall be used?

A: USG Cavity Shaft Wall can be used in elevator and mechanical shafts, air ducts, stairwells, and areas where wall construction is only available from one side. In addition, USG Cavity Shaft Wall can be used to provide horizontal protection for corridor ceilings, underside of stairwells, and other applications.

Q: Can USG Cavity Shaft Wall be used for vent shafts?

A: Yes. USG Cavity Shaft Wall vertical vent shaft assembly rated 2 hours per UL Design Number U529.

Q: Where can Double E studs be placed?

A: Do not locate the splice in the middle 1/3 of the span.

Q: How do I install the USG Cavity Shaft Wall?

A: The wall should be installed from floor to floor.

Q: Can Double USG E-studs be spliced?

A: Yes. We recommend that the splice not be located in the middle 1/3 of the span. Please refer to System Catalog (SA926) for additional information.

Q: In a USG Cavity Shaft Wall can 5/8" SHEETROCK^® Brand Gypsum Panels, FIRECODE Core (Type X), be substituted for 1/2" SHEETROCK^® Brand Gypsum Panels, FIRECODE C Core?

A: Yes.

Q: Is it necessary to tape the joints of the 1" SHEETROCK Brand Gypsum Liner Panel in a USG Cavity Shaft Wall assembly?

A: No. The joints do not require tape, however it is necessary to stagger the joints of the liner panels. Please refer to System Folder System Catalog (SA926) for detailed information on this application.

Q: Can you use Shaft Wall in a curved condition?

A: The system does not lend itself for tight radii. A 50 radius has been done, but anything less would require the assistance of the USG Architectural Services group. They can be contacted at 1-800-USG-4-YOU (800-874-4968).  

Q: How are the Double USG E-studs attached?

A: Fasteners should be located at both ends, and staggered 12 inches or closer the full length of the studs.

Q: In the literature piece SA926 in the base section detail there is a piece of gyp board at a 75 minimum angle. What is this for and is it required?

A: When the slab extends over 2? from the interior side of the Shaft Wall that piece is there to offer protection from things falling onto the ledge and to provide safety to ensure nothing can sit or be left there. It does not have an effect on the fire rating.

Q: Can studs be substituted in UL design test number?

A: Yes. It is possible to substitute studs as long as the stud is of thicker gauge, size, or both.

Q: What is the limiting height of the USG Cavity Shaft Wall?

A: The limiting height is based upon the stud size and gauge, allowable deflection and air pressure load. System Catalog (SA926) - PDF contains a limiting heights chart.

Q: Can you test a wall assembly horizontally to acquire a fire rating for a ceiling?

A: Not in general. The exception is the SHEETROCK® Brand Shaft Wall, which is the only wall assembly that can be tested for ceilings by testing it horizontally.

Q: Is it possible to substitute Type C for Type X?

A: Yes. Type C can be used in place of Type X, but Type X cannot be used in place of Type C.

Q: How is the air pressure load determined? If I am not using the USG Cavity Shaft Wall in an elevator shaft, can I work off of the 5 psf pressure load?

A: The elevator cab speed and the number of elevators per shaft determine the air pressure load. Yes, if not enclosed in an elevator shaft you can work off the 5 psf pressure load.

Q: How can a fire rating be achieved with access to only one side of a partition?

A: A shaft wall can be built in front of the existing partition. This system can be used for ratings of up to 4 hours.

Q: How do I treat the horizontal butt joints of the 1" SHEETROCK® Brand Gypsum Liner Panels in a USG Cavity Shaft Wall?

A: The Fire Resistance Rating does not require any joint finishing of the horizontal butt joints of the 1" Liner Panels. We do recommend for heights over 12 feet the horizontal butt joints be staggered for proper structural integrity of the wall system. Please refer to USG Cavity Shaft Wall System Catalog (SA926) for additional information.  

Q: Does USG offer a 3hr rating for Cavity Shaft Wall?

A: Yes, U415.

Q: What structural header is required above a two-hour fire damper located within a two-hour fire rated USG Cavity Shaft Wall system?

A: The design of structural members containing fire damper assemblies is normally the responsibility of the fire damper manufacturer, and not USG. This is for proper operation of the fire damper during a fire.

Q: Is the THERMAFIBER insulation necessary? Can I substitute fiberglass insulation?

A: There are designs that require THERMAFIBER insulation to achieve the fire rating. Check the UL Fire Resistance Directory for the specific design requirements. In other assemblies, the THERMAFIBER insulation is used to increase the STC. Fiberglass insulation cannot be substituted for THERMAFIBER insulation.

Q: What type of fire rating can I get with a USG Cavity Shaft Wall?

A: USG Cavity Shaft Walls provide UL tested 1 to 4-hour fire resistance.