Seismic Solutions

Introduction to Seismic Solutions

Seismic compliance

Seismic compliance refers to the use of approved systems and designs that meet the seismic design requirements of a building project to provide life safety to occupants and maintain building function during and after an earthquake. Nonstructural components represent a high percentage of a project’s capital investment. Failure of these components in an earthquake has the potential to cause harm, block egress and impede rescue efforts, and can disrupt the building’s function. The basic objectives of seismic design for nonstructural components are to provide life safety, minimize property loss and prevent functional loss.


The following are all the IBC Category D, E, and F2 Code Requirements for lay-in acoustical panels and direct-hung acoustical tiles. The specifications below are for standard applications. View an alternate solution that delivers additional options.


Basic Connections, Perimeter, and Lateral Splay BracingRequirements
Minimum intersection strength limits @ MT / CT180 lbs
Vertical hanger wire 12-gauge @ 4' o.c.Required
Connection device from vertical wire to the structure above must sustain min 100 lbsRequired
Main tee classificationsHeavy-duty 
1 in 6 max plumb of vertical hanger wiresRequired
Perimeter vertical hanger wires not more than 8" from wallRequired
Grid end/wall clearanceMin 3/4"
Perimeter closure (molding) widthMin 2 "
Grid connection to perimeter attached on two adjacent wallsRequired
Perimeter tee ends tied togetherRequired
Horizontal restraint (splay wires or rigid bracing) within 2" of intersection and splayed 90° apart at 45° anglesRequired
Compression posts (struts) 12' o.c. in both directions, starting 6' from wallsRequired
Splay bracing connection strength 200 lbs or the design load, whichever is greaterRequired
Partition attachmentBracing independent of ceiling splay bracing
Seismic separation joint4Required for areas > 2,500 sq. ft. (or full height partition)
Rigid bracing for ceiling plane elevation changesRequired


Light Fixture AttachmentRequirements
Light fixture (all types) mechanically attached to grid NEC 410-16 (two per fixture unless independently supported)Required
Surface-mounted fixtures attached to gridNot required
Pendant-hung fixtures directly supported from structure with 9-gauge wire (or approved alternative)Required
Rigid lay-in or can light fixtures-
? 10 lbs – one wire to structure (may be slack)Required
11 to 56 lbs – two wires from housing to structure (may be slack)Required
? 57 lbs – supported directly to structure by approvedRequired


Light Fixture Supplementary Hanger WiresRequirements
Intermediate Duty Main Tees with cross tee rating below 16 lbs./LFRequired
Min. 12-gauge hanger wires must be attached to the grid members within 3 inches of each corner of each light fixture.-
Heavy Duty Main Tees with cross tee rating below 16 lbs./LFRequired
Min. 12-gauge hanger wires must be attached to the supporting cross tee within 3 inches of the corner of each light fixture.-
Supplementary hanger wires for Heavy Duty Main Tees with cross tee rating equal to 16 lbs./LFNot Required


Service ApplicationRequirements
Air terminals-
? 20 lbs – positively attached to gridRequired
21 to 56 lbs – positively attached to grid and two wires to structure (may be slack)Required
? 57 lbs – directly supported to structureRequired
Sprinkler heads and other penetration clearanceMin 2" dia. opening or a swing joint
Cable trays and electrical conduit independently supported and bracedRequired



  • Refers to CISCA installation recommendations for zones 3-4 via ASCE 7.
  • The above information is correct to the best of our knowledge at the date of issuance. Because codes continue to evolve, check with a local official prior to designing and installing a ceiling system. This is only intended as a quick reference.
  • Required for ceilings larger than 1,000 square feet.
  • Where substantiating design calculations are not provided.
  • USG DONN DXT 15 and DX 24 grid Heavy Duty meet this requirement