Hanging Requirements for Lighting Fixtures in Earthquake Areas

Surface-Mounted Lighting

• For lighting fixtures installed flush with the ceiling, compliance with codes is mainly done in the support system in the ceiling. Fixtures must have slack safety wires leading from the clamping device holding the lighting fixture and the nearest ceiling hanger. Fixtures under 10 pounds need only one safety wire; those between 10 and 56 pounds need two safety wires set diagonally to each other. For fixtures more than 56 pounds, the guidelines for heavy lighting fixtures including anchoring the lighting fixture in a concrete slab.

Pendant Lighting

• Hanging pendant lighting fixtures will depend on the location of the lights. Schools have stricter rules governing the support system around a pendant light. You need to hang the light with cable that can hold at least twice the weight of the fixture. As with other lighting fixtures, the light must be supported directly in a joist or other part of the of the building's framing. Use a safety chain and bulb covers to upgrade older pendant lighting. If the fixture is in a position where it would swing wildly during an earthquake and hit other structures, you need to add restraint wires.

Recessed Lighting

• Recessed lighting fixtures are completely within the ceiling. The support for such lights are unseen, but still just as important as with other fixtures. Recessed lights should be supported in at least two positions to the ceiling grid so either attachment can hold the entire weight of the light. You'll need additional safety wires as a backup support; keep these wires slack. The number of wires is the same as for surface-mounted lighting. Add horizontal bracing of the lighting fixture, accomplished with splay wires attached at the corners of the fixture. Restrain the bulb and glass of the fixture to keep them from falling.

Heavy Lighting Fixtures

• Heavy fixtures include those weighing more than 56 pounds. You must hang these carefully because their large size can be lethal if a light falls on a person during an earthquake. Expansion anchors hold the lighting fixture to a 4-inch thick concrete slab. Vertical stiffeners or a pipe support the heavy lighting fixture between the top of the ceiling and the concrete slab above. These are attached to steel plates on both ends. Threaded rod hangers separate the 4-inch space between the bottom steel plate in the ceiling and the mounting plate for the fixture.