Electrical Work in London Homes: Part P, Rewiring, Consumer Units, and What Requires a Qualified Electrician

Key Takeaways

• ✓Part P of the Building Regulations (England) covers electrical safety in dwellings. It requires that certain types of electrical work in dwellings (and outbuildings and garden) must be either: carried out by a "competent person" who is registered with a Government-approved competent person scheme (CPS) — such as NAPIT, NICEIC, or ELECSA — and who self-certifies the work (notifying the local authority Building Control on the homeowner's behalf and issuing a completion certificate); or notified to the local authority Building Control before the work begins, with the work then inspected and certified by a Building Control inspector. "Notifiable" electrical work under Part P includes: new consumer unit installation or replacement; installation of a new circuit (adding a new circuit from the consumer unit to a new location); addition of new wiring in certain locations (special locations — kitchens, bathrooms, and outdoors — where water and electricity are more likely to come into contact); installation of a new fuseboard (consumer unit) in a special location. "Non-notifiable" (exempt) work includes: adding a new socket outlet or light fitting to an existing circuit (not in a special location); adding a spur to an existing circuit; replacing like-for-like accessories (sockets, switches, light fittings) in the same position. For practical purposes, any electrical work beyond the simplest replacement or addition should be carried out by a NICEIC/NAPIT/ELECSA registered electrician who can self-certify the work and provide the required certificates
• ✓The EICR (Electrical Installation Condition Report — formerly called a Periodic Inspection Report or PIR) is an assessment of the condition and safety of an existing electrical installation. An EICR is carried out by a qualified electrician or approved electrical inspector (typically a NICEIC or NAPIT registered contractor) who inspects, tests, and reports on the existing fixed wiring, consumer unit, earthing and bonding arrangements, and all fixed electrical accessories. The EICR identifies: C1 observations (Danger present — immediate action required); C2 observations (Potentially dangerous — urgent remedial action required); C3 observations (Improvement recommended — not immediately dangerous but below modern standards); and FI observations (Further investigation required — cannot be completed without further investigation). An EICR for a standard 3-bedroom London Victorian terrace typically takes 3–5 hours and costs £150–£350. An EICR is required: by landlords for all privately rented properties (legally required every 5 years or at change of tenancy since July 2020 for new tenancies and April 2021 for all rented properties); when buying an older London property (strongly recommended before exchange of contracts to identify any electrical safety issues that may affect the offer price or the insurance position); and before carrying out significant building works to a property (to establish the baseline condition of the existing electrical installation and identify any safety issues that should be addressed as part of the building works project). An EICR will typically recommend that properties with rubber-insulated cables, asbestos-insulated wiring, aluminum wiring, or an old fuseboard without RCD protection be rewired as the appropriate action to bring the installation to a satisfactory standard
• ✓Full rewiring of a London Victorian terrace is required when: the existing wiring is rubber-insulated (the rubber insulation in pre-1965 wiring becomes brittle with age and can crack, exposing live conductors — a fire and electrocution risk); the wiring is old-style lead or aluminium cable (lead-sheathed or lead-insulated cables, or aluminium wiring from the 1960s–70s which is prone to overheating at connections); the installation has no RCD (Residual Current Device) protection (RCDs detect earth faults and disconnect the circuit in milliseconds, preventing electrocution — an installation without RCDs is a significant safety deficiency); the consumer unit is an old-style rewirable fuse board (where the protection is provided by cartridge fuses or rewirable wire fuses rather than miniature circuit breakers — MCBs). A full rewire involves: stripping out all of the existing fixed wiring; installing new twin-and-earth PVC-insulated cables, or (in some applications) SWA cables or flexible conduit; installing a new consumer unit with MCB protection on all circuits, RCD protection (typically by way of dual-RCD or RCBO protection throughout), and surge protection where specified; and reinstatement of all lighting and power accessories. A full rewire of a 3-bedroom Victorian terrace in London typically costs £3,500–£7,000 for the electrical work alone (excluding plastering and decoration of the inevitable cable routes and first-fix penetrations), and takes 3–7 days on site
• ✓Consumer unit replacement (upgrading an old fuse board to a modern consumer unit) is one of the most common electrical works in London Victorian terraces. The current standard consumer unit for UK domestic installations is a metal-clad consumer unit (since the 2019 amendment to BS 7671 — the 18th edition of the IET Wiring Regulations — required consumer units in domestic dwellings to be metal-clad to reduce the fire risk from consumer unit faults, which had been identified as a cause of house fires where plastic consumer units were used). A modern consumer unit should include: RCD protection on all circuits (either dual-RCD split-load protection, where circuits are split between two RCDs, or individual RCBO protection for each circuit — which avoids "nuisance tripping" where a fault on one circuit trips the RCD and cuts power to multiple circuits); surge protection devices (SPDs) — recommended for new installations and increasingly specified as standard; and correctly rated MCBs for each circuit (typically 6–10A for lighting circuits, 20A for ring main circuits, and specific ratings for cooker, shower, and other dedicated circuits). A consumer unit replacement for a standard 3-bedroom London Victorian terrace (replacing an old fuse board with a new metal-clad consumer unit, upgrading to RCD protection, with new circuits as required) typically costs £800–£1,800 supply and install, plus the cost of any additional cable renewal or circuit additions identified during the work
• ✓First-fix and second-fix electrical work is the standard sequencing for electrical installation in a building project. First-fix electrics (the work carried out before plastering and finishing): installing all cable routes (chasing channels in masonry walls, drilling joists for cable passage through floors, clipping cables on exposed surfaces before they are enclosed by plasterboard); installing all back boxes (for sockets, switches, and consumer unit); positioning the consumer unit enclosure; running cables to all final circuit positions. First-fix electrics should be inspected and tested by the electrician (for continuity and insulation resistance) before plastering to confirm that no cable damage occurred during the first-fix installation. Second-fix electrics (the work carried out after plastering, painting, and flooring): installing all socket and switch accessories; installing light fittings; connecting all circuits at the consumer unit; testing and commissioning the complete installation; issuing the Electrical Installation Certificate (EIC). The sequencing of first-fix and second-fix electrics within the wider building programme is a critical coordination point — the first-fix must be complete (and approved) before plastering and boarding, and the consumer unit must be energised before second-fix testing can be completed. On a full house refurbishment or loft conversion project, the first-fix electrical programme typically overlaps with the first-fix plumbing and carpentry programme