Health and Safety

Taking care with materials, equipment and work procedures and dealing with hazards.

Electrical safety

Electrical power use on building sites is particularly hazardous because of the need to use cables and flexible extension cords, and the power is often used in damp conditions.

Precautions must be taken to protect workers from electric shock, electrocution, fires and explosions.

On this page:

  • precautions when using power
  • safeguards for electrical supply
  • temporary supply switchboards
  • electrical equipment inspection
  • underground and overhead power lines
  • fitting insulation under a suspended floor.

Precautions when using power

Precautions when using power on a building site include:

  • do not overload circuits
  • do not used damaged flexible extension cords
  • keep flexible extension cords away from sharp edges
  • do not use electrical equipment in wet conditions
  • use equipment suitable for the working environment, e.g. cordless tools for damp conditions.

Safeguards for electrical supply

If a portable electrical appliance is used in damp situations, it must have the following safeguards:

  • An isolating transformer with a voltage between conductors not exceeding 230 volts.
  • Double insulation to the appliance.
  • A source to earth connection so that the earth voltage does not exceed 55 volts.
  • A residual current device (RCD). An RCD monitors the electric current flowing through a circuit. If you touch a live wire or faulty equipment and electricity flows through you to the ground, the RCD senses the reduction in current and shuts off the electricity. This reduces the risk of a serious or fatal injury.

Temporary supply switchboards

Temporary supply switchboards on building sites should:

  • be solidly constructed
  • be fixed to a permanent or specifically designed structure
  • should be weathertight for safe operation where installed outdoors
  • include an insulated slot in the bottom for cables and leads to feed through
  • provide a stand for the support of cables and flexible extension cords
  • have a door that can be locked, will not damage flexible cords and protect switches from mechanical damage.

Electrical equipment inspection

Electrical equipment on building sites must be tested and tagged every 3 months. See standard AS/NZS 3012:2010 Electrical installations - Construction and demolition sites. The tag should give the date of the inspection and the next date an inspection is due.

Underground and overhead power lines

When carrying out an excavation, always assume that cables will be present. Take precautions against striking underground cables by confirming the location of underground cables (and other services) and obtaining up-to-date electrical plans for adjacent buildings.

If working close to underground or overhead cables:

  • have the power temporarily disconnected by the utility company
  • do not allow any part of a crane, digger, excavator, drill rig or other mechanical plant, structure or scaffold closer than 4.0 m to an overhead line without the written consent of the power line owner.

Fitting insulation under a suspended floor

Power cables are often run along bearers and joists under a suspended floor. When installing underfloor insulation with steel staples turn off the power at the mains if there are electric cables present as it is extremely important not to staple through a live electricity cable electrocution can result. Four New Zealanders have died after doing this, and others have been injured. The practice of retrofitting or repairing foil insulation under floors was banned on 1 July 2016.


Updated: 18 October 2016