Standard Seismic Applications Guide - IBC Category C

The following are all the IBC Category C2 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 / CT3
 

60 lbs

  • Vertical hanger wire 12-gauge @ 4' o.c.
 

Required

  • Connection device from vertical wire to the structure above must sustain min 100 lbs
 

Not Required

  • Main tee classifications
 

Intermediate- or heavy-duty

  • 1 in 6 max plumb of vertical hanger wires
 

Required

  • Perimeter vertical hanger wires not more than 8" from wall
 

Not required unless molding < 7/8"

  • Grid end/wall clearance
 

Min 3/8"

  • Perimeter closure (molding) width
 

Min 7/8" (or use perimeter wires)

  • Grid connection to perimeter attached on two adjacent walls
 

Not Permitted

  • Perimeter tee ends tied together
 

Required

  • Horizontal restraint (splay wires or rigid bracing) within 2" of intersection and splayed 90° apart at 45° angles
 

Not Required

  • Compression posts (struts) 12' o.c. in both directions, starting 6' from walls
 

Not Required

  • Splay bracing connection strength 200 lbs or the design load, whichever is greater
 

Not Required

  • Partition attachment
 

Allowed only if ceiling is able to move laterally

  • Seismic separation joint4
 

Not required

  • Rigid bracing for ceiling plane elevation changes
 

Not 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

 

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 3/8" on all sides

  • Cable trays and electrical conduit independently supported and braced
 

Not Required

 

Notes

  1. Refers to CISCA installation recommendations for zones 0-2 via ASCE 7. Max ceiling weight: 2.5 psf.
  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. All USG DONN® brand ceiling suspension systems meet these requirements.
  4. Per ASTM C635.

Suspended Ceiling Seismic Assemblies Guide