The Seven Steps
Suspended Ceilings

The Problem

Unbraced acoustic-tile ceiling systems can shake loose during earthquakes. Heavy light fixtures and duct vents are particularly hazardous to occupants if they are not properly connected to the roof or the floor above (see drawings below). Unbraced ceilings can hit fire sprinkler heads, which may release water and flood the building.

This building sustained extensive interior nonstructural damage during the 1994 Northridge earthquake. Parts of the ceiling grid and tiles have fallen.
Source: Wiss, Janney, and Elstner Associates

How to Identify It

Lift a ceiling tile and look up into the space above the ceiling. If the tiles seem loose in their frames, they may fall when the building begins to move. In rooms more than 12 feet wide, you should see diagonal wires and vertical pipe struts connecting the ceiling tiles’ framework to the building’s framing above, spaced every 12 feet.

Look for wide, secure supports for the ceiling framework around the room’s edges.

Each light fixture and duct vent should be securely supported with at least two wires to the building framing above.

What Can Be Done

Wire hangers and braces can be added to ceiling systems, light fixtures, sprinklers, and vents. You can either make the additions yourself or hire a contractor (see below for instructions).

Make sure there are gaps that will allow pipes to move where they pass through ceilings and partitions.

Bracing ceilings – This view from the top of the ceiling tiles shows diagonal bracing and struts to keep the tiles from falling in earthquakes.
Source: California Office of Emergency Services

Lighting fixtures – Fluorescent lighting fixtures should be secured so they will not present hazards.
Source: California Office of Emergency Services

General Recommendations

  • Provide splay brace wires and compression struts.
  • Separate the edges of suspended ceilings from enclosing walls.
  • Secure lay-in tiles and boards used in ceiling grids with clips at exitways and corridors.

Typical Ceiling Grid
Source: Noson, Perbix, SSD

Supplies Required

  • Wire—No. 12 gage
  • Adjustable compression struts
  • Ceiling panel clips

Installation

  1. Install splayed wires at 12′ on center in four directions.
  2. Provide adjustable compression struts, at center of splayed wires, and attach to the structure above.
  3. Provide ceiling tile clips at exits and stairwells.
  4. Provide 1/2″ minimum separation between the ceiling system and the enclosing walls.

Seismic Separation Around Suspended Ceiling
Source: Noson, Perbix, SSD

Suspended ceilings in concrete and steel buildings.

Ceiling Supported by Steel Framing
Source: Noson, Perbix, SSD

Ceiling Supported by Concrete Framing
Source: Noson, Perbix, SSD

Caution

When anchoring to post-tensioned slab, locate and avoid reinforcing.

Supplies Required

  • Wire—No. 12 gage
  • Adjustable compression struts
  • Eye-bolts with expansion inserts—3/8″ diameter

Installation

  1. Install splay wires at 12′ on center in four directions (see “Typical Ceiling Grid” graphic above for layout).
  2. Attach adjustable compression struts, placed at the center of the splayed wires, to the structure above.

Suspended ceilings in wood buildings.

Wire to Blocking
Source: Noson, Perbix, SSD

Wire to Joists
Source: Noson, Perbix, SSD

Wire to Joists with Eye Screws
Source: Noson, Perbix, SSD

Supplies Required

  • Wire—No. 12 gage
  • Staples—No. 9 gage, 1-1/2″
    OR
    Stronghold J nails
  • Eye-screws—1/4″ diameter
  • Nails—16 penny common
  • 2x blocking
  • Adjustable compression struts

Installation

  1. Install splay wires at 12′ on center in four directions with staples, J nails, or eye-screws (see “Typical Ceiling Grid” graphic above for layout).
  2. Install 2x blocking between joists with common nails, where required for the attachment of splayed wires.
  3. Provide adjustable compression struts, at center of splayed wires, to the structure above.
© 2024 Statewide California Earthquake Center (SCEC), headquartered at the University of Southern California (USC)