Electrical Hazards During Demolition

Demolition and renovation workers are often killed or hurt when they cut, break or pull into energized wiring they didn’t know was there. Old buildings have undocumented circuits, back-fed power, hidden junction boxes and live service lines. Water from firefighting or demolition dust makes everything worse. Knowing where power is, and shutting it off and proving it dead, is the first step of any demolition.

• Demolition Crews
• Renovation Workers
• Electricians
• Laborers

Why demolition is high-risk for electrical contact

• Unknown wiring: older buildings may have wiring that is not on any plan, or that was changed many times. Abandoned wiring may still be live or be re-energized by another circuit.
• Backfeed: generators, solar systems, battery systems, tenants or neighboring buildings can send power back into wiring that appears dead. See Standby Generators and Battery Energy Storage.
• Damaged insulation and exposed conductors from tearing out walls, ceilings and floors, and from machines like excavators, grapples and hammers.
• Wet conditions: water from rain, fire hoses, dust suppression and broken pipes can make live parts deadly. See Wet Locations.
• Overhead and underground services: service drops, feeders and buried lines can be hit by machines and falling material. See Overhead Power Lines, Underground Power Lines and Equipment Contact With Power Lines.
• Hazardous materials mixed in: asbestos-wrapped wires, lead and PCB-containing equipment, and mercury switches. See Asbestos.
• Structural collapse can bring down live conductors onto workers and equipment.

Survey and planning before work starts

• Do an engineering survey of the building and its utilities before demolition, as OSHA’s demolition rules require, and identify all electrical services, panels, feeders, transformers, generators and other sources. See Demolition Workers.
• Get utilities shut off and capped. OSHA requires that utility services be shut off, capped or otherwise controlled at or outside the building before demolition begins (29 CFR 1926.850). Contact the electric utility to disconnect the service, meter and service drop, and get written confirmation.
• Call 811 and arrange for locating of underground lines, and consider private locates for buried lines on the property. See Call 811 and Private Utility Locating.
• Identify all circuits and sources in the building, including those serving fire alarms, emergency lighting, elevators, other tenants and rooftop equipment. Mark panels and circuits, and map what will stay energized, if anything.
• Write a plan for who will de-energize, lock out, test and remove electrical equipment, and in what order. Use a qualified electrician for this. See Qualified vs. Unqualified Persons.
• Plan temporary power for tools and lighting, from a separate GFCI-protected source, and keep it away from demolition debris, water and machinery. See Temporary Power and GFCI Protection.
• Check for hazardous materials before disturbing wiring and equipment, and plan for safe handling and disposal.

De-energize, lock out and verify

• Treat every conductor as live until it’s tested and proven dead. Never assume a circuit is dead because the lights are off or because a panel is labeled.
• Shut off at the source and lock out and tag out each disconnecting means. See Lockout/Tagout.
• Test for absence of voltage at the point of work with a rated tester, which you check on a known source before and after. See Absence-of-Voltage Testing and Test Meters.
• Ground and short conductors where there is a chance of backfeed or induced voltage, as the electrical program requires.
• Cut off the service outside the building where possible, so the entire building wiring is isolated. Remove meters and service conductors as the utility directs.
• Keep control of the locks. Re-verify after shifts, breaks and weather events, and anytime a circuit could have been changed. Don’t remove another person’s lock.
• If power must stay on for part of the building, clearly separate and protect live parts, mark them and keep demolition away from them. Use qualified persons and follow energized work rules. See Energized Work Permits.

Removing wiring and equipment

• Remove electrical equipment first (soft stripping), by qualified persons, before heavy demolition. Cut and cap or remove wire, and remove panels, lighting and devices. Use insulated tools and appropriate PPE.
• Don’t cut unknown wires or conduit with a saw, torch or machine. Identify each cable and test it first. See Cable & Wire Rope Cutters and Hidden Wiring.
• Watch for transformers, capacitors and batteries that can hold stored energy after disconnect, or contain oil with PCBs. See Capacitors and Transformers.
• Don’t use equipment near live lines. Keep excavators, cranes, booms and wrecking attachments at safe distances, and use spotters. See Excavators.
• Protect workers from hazards from cutting and torches when electrical conduit and boxes are removed, including fire from sparks and hot work. See Hot Work Permits.
• Use GFCI protection on temporary tool circuits and keep cords out of water and debris.
• After removing equipment, remove or cap all remaining conductors, so no one can be exposed to live ends later.

Wet conditions and emergencies

• Water and electricity are deadly together. Shut off power before using water for dust control or in a flooded building, and stay out of water near energized equipment. See Electrical Injuries.
• If a machine contacts a live line, the operator should stay in the cab and warn others to stay away, unless there is a fire. See Downed Power Lines.
• Know emergency procedures, including calling the utility and 911, and the location of first aid. See Electric Shock Response.
• Workers hit by electricity should be treated as having serious injuries even if they seem fine.

Demolition electrical checklist

• A survey identified all electrical services and sources; utilities are shut off and capped, and confirmed in writing
• 811 was called; underground and overhead lines are located and protected
• Every circuit is locked out, tested dead and verified again after breaks and weather changes
• Only qualified people remove wiring, panels and equipment, and unknown cables are never cut by guess
• Temporary power is separate and GFCI-protected, away from water and debris
• Machines and spotters keep a safe distance from any live lines

Last updated: October 5, 2026