Seismic FAQs

How have the seismic codes changed in the last several years?

In the past, seismic force levels were only considered in certain earthquake-prone locations. But major revisions to the International Building Code (IBC) have changed the requirements, which now mandate that every construction project must include and meet a seismic design category, even those that have not required seismic installations in the past.

What is the basis for determining the seismic requirements for a suspended ceiling?

Three factors must be taken into account: geographic location, soil condition and type of building. Over half of the U.S. is now considered to be at some level of risk for seismic activity, based on these criteria.

Where can I find information about all of the installation requirements in a seismic ceiling?

USG provides detailed information on installation requirements, as well as downloadable details.

As a contractor or architect, what documents should I have to help me determine seismic requirements?

The current version of ASCE7, and both CISCA publications—Guidelines for Seismic Restraint for Direct-hung Suspended Ceiling Assemblies (Zones 0-2) and Guidelines for Seismic Restraint for Direct-hung Suspended Ceiling Assemblies (Zones 3-4).

Do I need to use 2" wall angle?

IBC seismic design categories D, E, and F call for 2in. wall molding however many jurisdictions are allowing narrower 7/8in. wall angles with a seismic clip. Where the local code official allows a seismic clip with 7/8in. wall angle in IBC seismic design categories D, E, and F installations USG has the ACM7 seismic clip designed specifically for this purpose.

Which USG suspension systems can I use in a seismic application?

All main Donn suspension systems, AX, DX®/DXL™, Fineline® (DXF), Fineline® 1/8 (DXFF), Centricitee™ (DXT/DXLT), CE (Controlled Environment), DXSS, DXW, DXLA™, and ZXLA™ (Environmental), include the code-compliant heavy-duty main tee required for Seismic Design Categories D, E, and F or the code-compliant Intermediate Duty main tee required for Seismic Design Category C.

Which USG ceiling panels are seismic rated?

There are no seismic requirements for tile.

Does USG have a clip that makes it possible to use 7/8" wall molding in IBC seismic design categories D, E, and F construction?

Yes, it is called ACM7.

Why can USG's IBC seismic design categories D, E, and F alternate construction methods carry more weight than competing systems?

Seismic testing typically focuses on the suspension system, without minimum weight requirements for ceiling panels and no requirement to include components such as light fixtures and air handling equipment. On the job, however, the suspension system must support and carry the weight of a fully functional ceiling, including ceiling panels that can weigh up to 2 lb./sq. ft. or more. For this reason, USG tested suspension systems with light fixtures, air handing equipment, and a wide range of USG ceiling panels. This full-scale testing certifies that USG IBC-compliant assemblies accommodate loads 39% heavier than those claimed by competing systems. As demonstrated by these superior test results, no other suspension system can match the tightness and seismic performance of USG suspension systems.

Why is USG so active in seismic research?

USG has a long history of supporting the development and research of seismic ceiling design and application, and we remain committed to this endeavor through product development, participation in industry associations, and supporting the evolution of building codes as new knowledge and product technologies become available. In fact USG is the only manufacturer that continues to perform seismic qualification tests with both the University at Buffalo (SUNY), the Department of Civil, Structural and Environmental Engineering – Structural Engineering and Earthquake Simulation Laboratory (SEESL) as well as the University of California, Berkeley, Earthquake Engineering Research Center (EERC). We are proud to commit significant resources to this ongoing endeavor.

Why do USG ceilings out-perform seismic requirements?

Since 1957 Donn suspension systems have set the standard, with the optimal combination of shape, size, steel gauge and connection details to produce the tightest systems available, with the greatest lateral and torsional stiffness. For these reasons, suspension systems from USG are proven to greatly exceed the lateral forces experienced in a seismic event.

Are there special requirements for hanger wires in seismic applications?

You can still use the same 12 gauge wire that you always have, but there may be additional requirements for how and where to place these wires. Please refer to SC2493 and SC2522 for more information.

What sort of materials can be used for seismic compression posts?

In addition to DONN® seismic compression posts, other options may include cold or hot rolled angles, loadbearing or non-loadbearing studs, EMT or rigid conduit, or black iron. The product used depends on the plenum size (length of the compression post). This should be determined either by a professional engineer or a registered architect. In some jurisdictions, the local building department will supply a list of acceptable products and the allowable lengths. (Link the Seismic Compression Post.)