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Standard Seismic Applications Guide - IBC Category D, E, F
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.
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| 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 |
Notes
- 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.