Rewiring a House in London: What's Involved, When It's Needed, and What It Costs

**Signs that a full or partial rewire is required**:

• •*Rubber-insulated cables (pre-1960s wiring)*: Single-core rubber-insulated cables (black rubber outer sheath, red and black cores inside) are over 60 years old and should be replaced — the rubber insulation has hardened and cracked with age, and the wiring is no longer safe under BS 7671 (the current wiring regulations). Identifiable by: the distinctive black rubber cable jacket visible at sockets, switches, and the consumer unit; or by a visual inspection of the loft or under-floor void where cables may be visible.
• •*Old consumer unit (fuse box) without RCDs*: An old rewirable fuse unit (with porcelain fuse holders and wire fuses) or an early MCB (miniature circuit breaker) board without RCD (residual current device) protection should be replaced. RCDs protect against electric shock — they detect earth leakage current and disconnect the circuit within 40ms (fast enough to prevent cardiac arrest). Current regulations require RCD protection on all final circuits in domestic premises.
• •*Single-socket outlets throughout*: Victorian and Edwardian properties were wired with a small number of single sockets (the era before high-demand electrical appliances). Modern households require multiple twin sockets in every room — 4–8 sockets in a kitchen alone, 4+ in a bedroom for device charging. A property with only single or very few sockets in each room almost certainly has an outdated installation.
• •*Lack of earthing or inadequate earthing*: Old wiring systems may have poor earthing — the cable from the electricity meter to the consumer unit may not include an earth conductor, or the earth bonding to the water and gas services may be missing or inadequate.
• •*Periodic Electrical Inspection Report (EICR) recommending rewire*: An EICR (formerly known as a periodic inspection report or periodic electrical test) by a registered electrician grades observations from C1 (danger present) through C2 (potentially dangerous) to C3 (improvement recommended) and FI (further investigation). A report with multiple C2 observations typically indicates a rewire is advisable.
• •*Burning smell, flickering lights, or tripping circuits*: Symptomatic of a failing installation — these require immediate attention.

**When is a partial rewire sufficient?**

• A full rewire (replacing all cables throughout the house) is not always required:
• •If the wiring is post-1960s PVC-insulated cable in generally good condition, but the consumer unit is old and lacks RCD protection: replace the consumer unit with a modern dual-RCD or RCBO (residual current breaker with overload) board — cost £400–£800 for a consumer unit change by a registered electrician
• •If first-fix wiring in a specific area is being replaced as part of a kitchen or bathroom renovation (new circuits for the new kitchen), the rest of the house may be left in place if the EICR is satisfactory
• •If some circuits (particularly lighting circuits) are in good condition and newer circuits (sockets, kitchen, bathroom) are in poor condition, a selective rewire of the poor circuits may be appropriate

**What a full rewire involves**:

**First-fix electrical works**:

1. *Consumer unit removal and connection isolation*: The existing consumer unit is isolated and removed; the new consumer unit position is agreed (should be accessible to all occupants, near the main entry point if possible, avoiding bathrooms and gas meter locations) 2. *Cable installation*: New twin-and-earth PVC-insulated cable is installed for every circuit throughout the house: • *Ring final circuits*: The standard UK domestic socket circuit — a ring of cable starting at the consumer unit, visiting all socket outlets in a floor zone, and returning to the consumer unit; typically 2.5mm² twin-and-earth cable; maximum 100m² floor area per ring • *Lighting circuits*: Radial circuits (one-way from consumer unit) for each floor's lighting; typically 1.0mm² twin-and-earth • *Radial circuits for high-demand appliances*: Separate dedicated circuits for: cooker/oven (6mm² or 10mm² depending on rating); shower (6mm² or 10mm²); electric vehicle charger (6mm²–10mm²); dishwasher; washing machine/tumble dryer; fridge-freezer • *Bathroom circuits*: Shaver socket; underfloor heating (if electric); extraction fan; towel rail • *Smoke alarm circuits*: Mains-wired interconnected smoke alarm circuit 3. *Back boxes*: New socket and switch back boxes (metal or plastic, flush or surface-mounted) installed at agreed positions 4. *Consumer unit installation*: New consumer unit installed at the agreed position, circuits terminated, RCDs or RCBOs installed

**Chasing and damage**:

• In a Victorian terraced house, new cables are typically installed either:
• •*In surface-mounted conduit* (on the surface of the walls — the quickest and least disruptive method, but visible until painted)
• •*Chased into the plaster or masonry* (a slot cut in the plaster or brick, the cable laid in the slot, and the slot made good with plaster — this is hidden in the finished wall but produces significant dust and requires re-plastering)
• •*Through the void* (through the loft or under-floor void, dropping down between joists to reach socket positions — clean and invisible but requires access to the void at every socket position)

The method of cable installation depends on: whether the house is being renovated at the same time as the rewire (renovation = chase into bare plaster or route via exposed joists, then finish over); or whether the house is occupied and decorated (surface conduit avoids the disruption of chasing but is less aesthetically clean).

**Second-fix electrical works**:

1. *Fitting socket faceplates*: Double sockets, data points, USB socket outlets, USB-C charging outlets — installed at each back box position 2. *Fitting lighting switch plates and pendants*: Lighting switch plates, dimmer switches if specified, ceiling roses and pendant cables, or down-light drivers and fittings 3. *Connecting cooker, shower, and appliance circuits* 4. *Bathroom accessories*: Shaver socket, heated towel rail connections 5. *Testing and commissioning*: Dead tests (insulation resistance, loop impedance) followed by live commissioning tests; the electrician produces an installation certificate (Part P Building Control notification)

**Building Regulations Part P**:

• Part P of the Building Regulations (Electrical Safety in Dwellings) requires that notifiable electrical work in dwellings either:
• •Is carried out by a registered competent person (NICEIC, NAPIT, or ELECSA registered) who self-certifies the work — the registration body notifies Building Control on the electrician's behalf; or
• •Is inspected and certified by a Building Control officer (this route is used when an unregistered electrician carries out the work — rare for domestic projects)

Notifiable work includes: new consumer unit; new circuit from the consumer unit; any work in a bathroom or kitchen; any work within 3m of a swimming pool. Non-notifiable work (that does not require Part P notification) includes: replacing existing sockets, switches, and light fittings (like-for-like replacement); adding a spur from an existing socket.

For a full rewire: always use a NICEIC or NAPIT registered electrician who can self-certify — the certificate is the proof of compliance required by Building Control, mortgage lenders, and conveyancers when the property is sold.

**Typical rewire costs for London homes (2025)**:

| Property size | Full rewire (first fix + consumer unit, exc. second fix fittings) | Second fix and fittings | Total (exc. client-supplied light fittings and socket faceplates) | |---|---|---|---| | 1-bed flat (50m²) | £2,000–£3,000 | £400–£700 | £2,400–£3,700 | | 2-bed terraced (70m²) | £2,500–£4,000 | £500–£900 | £3,000–£4,900 | | 3-bed terraced (90m²) | £3,500–£5,500 | £700–£1,200 | £4,200–£6,700 | | 4-bed semi-detached (120m²) | £4,500–£7,000 | £900–£1,500 | £5,400–£8,500 | | 5-bed detached (180m²+) | £6,000–£10,000 | £1,200–£2,000 | £7,200–£12,000 |

*Notes on inclusions*: First fix includes cable installation, back boxes, and consumer unit. Second fix includes socket faceplates, switch plates, and light fitting connections. *Excluded* (client-supplied per RCB's terms): light fittings, decorative socket faceplates above standard, USB socket upgrades, smart home devices.

**Additional circuits that add to the base rewire cost**:

| Circuit | Additional cost | |---|---| | EV charger circuit + trunking to garage/driveway | £400–£800 | | New consumer unit only (no rewire, existing circuits retained) | £400–£800 | | Electric vehicle OZEV-compliant charger installation | £900–£1,500 | | Smart home/lighting control system (Lutron, Control4 first fix) | £2,000–£8,000+ | | MVHR electrical connection and commissioning | £200–£400 |

**Programme: how long does a rewire take?**

| Property size | First fix duration | Second fix duration | Total | |---|---|---|---| | 1–2 bed flat | 2–3 days | 1 day | 3–4 days | | 3-bed terraced | 3–5 days | 1–2 days | 4–7 days | | 4–5 bed house | 5–8 days | 2–3 days | 7–11 days |

**Integrating a rewire with renovation works**:

The most cost-effective and least disruptive time to rewire a house is during a renovation when the walls and ceilings are being stripped back and re-plastered anyway. The rewire should be integrated into the renovation programme as follows:

1. *Demolition and strip-out*: Existing plaster removed where required for the renovation; existing electrical installation isolated and removed at this stage 2. *Structural works*: New beams, lintels, and structural elements completed — at this stage, chasing for cables through the structure is straightforward before new plasterboard is fixed 3. *Electrical first fix*: All cables, back boxes, and consumer unit installed while walls and ceilings are open — no chasing required, cables run through the open structure 4. *Plasterboard and plaster*: Walls and ceilings boarded and plastered over the first-fix installation 5. *Decoration*: Rooms decorated 6. *Electrical second fix*: Socket faceplates, switch plates, and light fittings fitted after decoration is complete