Rewiring a property involves replacing the fixed wiring that runs to sockets, lighting points, switches and other electrical accessories and outlets throughout the building. A full rewire covers the entire installation from the consumer unit outwards; a partial rewire addresses a defined section of the property, a single floor, or a number of identified circuits where the existing wiring is no longer serviceable.
Rewiring becomes necessary when the existing wiring has deteriorated to a degree where it cannot be safely repaired or upgraded on a circuit-by-circuit basis. Common triggers include the presence of rubber or lead-sheathed insulation, which becomes brittle and can crack or disintegrate with age; or an electrical installation condition check that has found widespread deterioration, inadequate protection or non-compliant installation methods across the property.
Older red and black conductor colours can indicate the age of wiring, but do not by themselves establish that it is unsafe or needs replacing. Inspection and testing determine its condition.
The practical process of rewiring involves routing new cables through the property. This typically requires lifting floorboards to access floor voids, chasing channels into plasterwork to conceal cables in walls, and working in roof spaces.
The extent of disruption depends on the size and layout of the property and whether existing cable routes can be reused. Plastering and making good of disturbed surfaces is generally carried out by a separate trade once the first-fix electrical wiring is complete.
Once all new cables are run and connected, the electrician carries out a full programme of tests before the installation is commissioned. New circuits installed as part of a rewire are notifiable under Part P of the Building Regulations in England, and Electrical Installation Certificates must be issued for the work.