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,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 Bracing Requirements    
Minimum intersection strength limits @ MT / CT 180 lbs    
Vertical hanger wire 12-gauge @ 4' o.c. Required    
Connection device from vertical wire to the structure above must sustain min 100 lbs Required    
Main tee classifications Heavy-duty     
1 in 6 max plumb of vertical hanger wires Required    
Perimeter vertical hanger wires not more than 8" from wall Required    
Grid end/wall clearance Min 3/4"    
Perimeter closure (molding) width Min 2 "    
Grid connection to perimeter attached on two adjacent walls Required    
Perimeter tee ends tied together Required    
Horizontal restraint (splay wires or rigid bracing) within 2" of intersection and splayed 90° apart at 45° angles Required    
Compression posts (struts) 12' o.c. in both directions, starting 6' from walls Required    
Splay bracing connection strength 200 lbs or the design load, whichever is greater Required    
Partition attachment Bracing independent of ceiling splay bracing  
Seismic separation joint4 Required for areas > 2,500 sq. ft. (or full height partition)
Rigid bracing for ceiling plane elevation changes Required    
Light Fixture Attachment Requirements    
Light fixture (all types) mechanically attached to grid NEC 410-16 (two per fixture unless independently supported) Required    
- Surface-mounted fixtures attached to grid Not 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 approved Required    
Light Fixture Supplementary Hanger Wires Requirements    
Intermediate Duty Main Tees with cross tee rating below 16 lbs./LF Required    
- 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./LF Required    
- 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./LF Not Required    
Service Application   Requirements
Air terminals  
≤ 20 lbs – positively attached to grid Required
21 to 56 lbs – positively attached to grid and two wires to structure (may be slack) Required    
≥ 57 lbs – directly supported to structure Required
Sprinkler heads and other penetration clearance Min 2" dia. opening or a swing joint  
Cable trays and electrical conduit independently supported and braced Required


1. Refers to CISCA installation recommendations for zones 3-4 via ASCE 7.
2. 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.
3. Required for ceilings larger than 1,000 square feet.
4. Where substantiating design calculations are not provided.
5. USG DONN DXT 15 and DX 24 grid Heavy Duty meet this requirement