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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.
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| 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 |
≤11 to 56 lbs – two wires from housing to structure (may be slack) | Not Required |
Cable trays and electrical conduit independently supported and braced | Required |
Notes
- Refers to CISCA installation recommendations for zones 0-2 via ASCE 7. Max ceiling weight: 2.5 psf.
- 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.
- All USG DONN® brand ceiling suspension systems meet these requirements.
- Per ASTM C635.