Full House Rewire for London Victorian Terraces: 18th Edition BS 7671, Consumer Units, and Part P

THE DECISION TO REWIRE A LONDON VICTORIAN TERRACE IS NOT ALWAYS STRAIGHTFORWARD — THE ELECTRICAL INSTALLATION MAY APPEAR TO FUNCTION WITHOUT PROBLEMS WHILE HAVING SIGNIFICANT HIDDEN SAFETY DEFICIENCIES. THE FOLLOWING INDICATORS STRONGLY SUGGEST THAT A FULL REWIRE IS REQUIRED RATHER THAN PARTIAL REPAIRS.

AGE OF INSTALLATION: ANY ELECTRICAL INSTALLATION IN A LONDON VICTORIAN TERRACE THAT HAS NOT BEEN FULLY REWIRED SINCE APPROXIMATELY 1960 SHOULD BE CONSIDERED FOR REWIRING. PRE-1960 WIRING MATERIALS (RUBBER-INSULATED WIRING — VIR — VULCANISED INDIA RUBBER — OR LEAD-SHEATHED WIRING) SHOULD BE CONSIDERED END-OF-LIFE AND REWIRED WITHOUT DELAY. 1960S-1970S PVC-INSULATED WIRING: STILL TECHNICALLY SERVICEABLE IN MANY CASES — BUT THE PVC INSULATION FROM THIS ERA (PARTICULARLY THE EARLY PVC FORMULATIONS WITH LOWER PLASTICISER CONTENT) IS OFTEN BRITTLE AND PRONE TO CRACKING WHEN DISTURBED — AN ELECTRICAL INSTALLATION CONDITION REPORT (EICR) BY A QUALIFIED ELECTRICIAN WILL IDENTIFY WHETHER THE CONDITION OF THE WIRING MERITS FULL REWIRING OR IS ADEQUATE FOR CONTINUED USE (WITH REPAIRS).

ELECTRICAL INSTALLATION CONDITION REPORT (EICR): AN EICR (ALSO KNOWN AS A PERIODIC INSPECTION REPORT) IS THE FORMAL ASSESSMENT OF AN EXISTING ELECTRICAL INSTALLATION BY A REGISTERED ELECTRICIAN — CLASSIFIED UNDER BS 7671 AS: C1 — DANGER PRESENT (IMMEDIATE RISK OF INJURY — MUST BE RECTIFIED IMMEDIATELY); C2 — POTENTIALLY DANGEROUS (REQUIRES URGENT ATTENTION — SHOULD BE RECTIFIED AS SOON AS POSSIBLE); C3 — IMPROVEMENT RECOMMENDED (NOT IMMEDIATELY DANGEROUS — BUT IMPROVEMENT WOULD BE BENEFICIAL); FI — FURTHER INVESTIGATION REQUIRED. AN EICR WITH C1 OR C2 CODES INDICATES THAT THE INSTALLATION IS NOT SAFE FOR CONTINUED USE WITHOUT RECTIFICATION — IN A LONDON VICTORIAN TERRACE WITH ORIGINAL OR EARLY REPLACEMENT WIRING, AN EICR TYPICALLY PRODUCES MULTIPLE C2 CODES RELATED TO: ABSENT OR INADEQUATE EARTHING; ABSENT OR INADEQUATE BONDING (OF GAS AND WATER SERVICES); ABSENCE OF RCD PROTECTION; OVERCURRENT PROTECTION INADEQUATE FOR THE INSTALLED CABLE SIZES; DETERIORATED WIRING INSULATION.

RENOVATION TRIGGER: A FULL REWIRE IS ALMOST ALWAYS THE CORRECT DECISION WHEN A LONDON VICTORIAN TERRACE IS UNDERGOING A COMPREHENSIVE RENOVATION — BECAUSE THE REWIRE IS MOST COST-EFFECTIVE WHEN THE WALLS AND CEILINGS ARE OPEN (DURING FIRST-FIX CONSTRUCTION PHASE — BEFORE PLASTERING OR DRYLINING) — REWIRING THROUGH CLOSED WALLS AND CEILINGS (THE ALTERNATIVE — CALLED A SURFACE REWIRE OR COSMETIC REWIRE) IS SIGNIFICANTLY MORE DISRUPTIVE AND EXPENSIVE FOR THE SAME END RESULT.

THE CONSUMER UNIT (THE MODERN EQUIVALENT OF THE FUSEBOX — CONTAINING THE MAIN SWITCH, THE OVERCURRENT PROTECTIVE DEVICES — EITHER MCBS OR RCBOS — AND THE RESIDUAL CURRENT DEVICES — RCDS) IS THE CENTRAL COMPONENT OF A REWIRED ELECTRICAL INSTALLATION IN A LONDON VICTORIAN TERRACE.

18TH EDITION BS 7671 REQUIREMENT FOR NEW CONSUMER UNITS (2018 AMENDMENT TO THE IET WIRING REGULATIONS — 18TH EDITION): ALL NEW CONSUMER UNITS INSTALLED IN DOMESTIC PREMISES MUST BE HOUSED IN A NON-COMBUSTIBLE ENCLOSURE (METAL ENCLOSURE — TYPICALLY STEEL POWDER-COATED GREY). THE REQUIREMENT FOR METAL CONSUMER UNITS WAS INTRODUCED IN THE 17TH EDITION AMENDMENT 3 (2015) AND IS MANDATORY UNDER THE 18TH EDITION — PLASTIC CONSUMER UNITS ARE NO LONGER PERMITTED FOR NEW DOMESTIC INSTALLATIONS.

HAGER VML910 (HAGER UK LTD — TELFORD, SHROPSHIRE — THE MOST WIDELY SPECIFIED CONSUMER UNIT IN UK DOMESTIC REWIRE PROJECTS 2023-2025 BY NICEIC DOMESTIC INSTALLERS): THE VML910 IS A 10-WAY DUAL RCD CONSUMER UNIT (TWO RCDs — EACH PROTECTING FIVE CIRCUITS — THE DUAL-RCD SPLIT-LOAD ARRANGEMENT IS THE MINIMUM 18TH EDITION STANDARD FOR NEW DOMESTIC INSTALLATIONS — PROVIDING DISCRIMINATION BETWEEN THE TWO RCD GROUPS SO THAT A FAULT ON ONE CIRCUIT DOES NOT TRIP ALL CIRCUITS SIMULTANEOUSLY). METAL ENCLOSURE (STEEL — GREY POWDER COAT). RATING: 100A ISOLATOR / 63A RCDS (TYPE AC — 30MA). CIRCUIT BREAKERS: 10 X MCB WAYS. PRICE (SUPPLY ONLY — WITHOUT CIRCUIT BREAKERS): APPROXIMATELY £60-90 (UK ELECTRICAL WHOLESALE — JTL, REXEL, CITYELECTRICAL FACTORS). LIMITATION: DUAL RCD PROVIDES GROUP-LEVEL PROTECTION — IF A CIRCUIT IN A GROUP DEVELOPS A PERSISTENT EARTH FAULT (E.G., A FAULTY APPLIANCE LEFT PLUGGED IN), THE ENTIRE GROUP OF 5 CIRCUITS IS DISCONNECTED. THE ALTERNATIVE (RCBO PROTECTION) PROVIDES INDIVIDUAL CIRCUIT PROTECTION.

SCHNEIDER RESI9 (SCHNEIDER ELECTRIC — GRENOBLE, FRANCE — THE MOST WIDELY SPECIFIED ALL-RCBO CONSUMER UNIT IN UK DOMESTIC INSTALLATIONS): THE RESI9 RANGE USES INDIVIDUAL RCBOS (RESIDUAL CURRENT CIRCUIT BREAKER WITH OVERCURRENT PROTECTION — AN RCBO COMBINES THE FUNCTIONS OF AN MCB + RCD IN A SINGLE MODULE — PROVIDING BOTH OVERCURRENT PROTECTION AND 30MA RCD PROTECTION FOR EACH CIRCUIT INDIVIDUALLY — SO A FAULT ON ONE CIRCUIT ONLY TRIPS THAT CIRCUIT'S RCBO — OTHER CIRCUITS ARE UNAFFECTED). ADVANTAGES: SUPERIOR DISCRIMINATION (A NUISANCE TRIP ON ONE CIRCUIT DOES NOT AFFECT ANY OTHER CIRCUIT — MAXIMUM CONVENIENCE FOR THE HOUSEHOLDER). DISADVANTAGE: HIGHER COST (EACH RCBO IS MORE EXPENSIVE THAN AN MCB — APPROXIMATELY £8-15/EACH FOR AN RCBO VS £3-6/EACH FOR AN MCB). FOR A TYPICAL LONDON VICTORIAN TERRACE REWIRE (12-16 CIRCUITS): SCHNEIDER RESI9 ALL-RCBO BOARD: £200-350 SUPPLY (BOARD + ALL RCBOS). HAGER VML910 DUAL-RCD + MCBS: £100-150 SUPPLY. THE ADDITIONAL COST OF AN ALL-RCBO BOARD OVER A DUAL-RCD BOARD IS APPROXIMATELY £80-200 — TYPICALLY RECOMMENDED FOR ALL NEW REWIRES IN A LONDON VICTORIAN TERRACE WHERE THE HOUSEHOLDER IS LIKELY TO HAVE ELECTRIC VEHICLES, SOLAR PV, ELECTRIC SHOWERS, AND MULTIPLE HIGH-CURRENT CIRCUITS.

A FULL REWIRE FOR A STANDARD LONDON VICTORIAN TERRACE (2-3 BEDROOMS — 2 STOREYS — REAR ADDITION) TYPICALLY INVOLVES 12-18 CIRCUITS — DESIGNED TO SEPARATE ELECTRICAL LOADS BY ZONE AND FUNCTION TO MINIMISE THE IMPACT OF A CIRCUIT FAULT AND TO MEET THE SPECIFIC REQUIREMENTS OF 18TH EDITION BS 7671.

STANDARD CIRCUIT LAYOUT FOR A LONDON VICTORIAN TERRACE (TYPICAL — 12-16 CIRCUIT REWIRE): RING MAIN CIRCUITS (20A MCBS/RCBOS — 2.5MM² TWIN AND EARTH CABLE — FORMING A RING FROM THE CONSUMER UNIT AND BACK AGAIN — PROVIDING POWER SOCKETS ON THE RING): (1) GROUND FLOOR RING (ALL SOCKET OUTLETS IN THE GROUND FLOOR RECEPTION ROOMS AND HALL). (2) FIRST FLOOR RING (ALL SOCKET OUTLETS IN THE FIRST FLOOR BEDROOMS AND LANDING). (3) KITCHEN RING (RING CIRCUIT DEDICATED TO THE KITCHEN — RECOMMENDED AS A SEPARATE RING FROM THE GROUND FLOOR RING BECAUSE THE KITCHEN HAS A HIGH ELECTRICAL LOAD FROM APPLIANCES). LIGHTING CIRCUITS (6A MCBS/RCBOS — 1.5MM² TWIN AND EARTH CABLE): (4) GROUND FLOOR LIGHTING. (5) FIRST FLOOR LIGHTING. (6) LOFT/ATTIC LIGHTING. DEDICATED HIGH-LOAD CIRCUITS (FIXED APPLIANCES REQUIRING THEIR OWN CIRCUIT): (7) COOKER CIRCUIT (32A OR 40A MCBO/RCBO — 6MM² CABLE — REQUIRED FOR ANY COOKER OR RANGE ABOVE 4KW). (8) DISHWASHER (13A FUSED SPUR — OR A 20A RADIAL FROM A DEDICATED CIRCUIT). (9) WASHING MACHINE (20A RADIAL — 2.5MM² CABLE — DEDICATED TO THE WASHING MACHINE). (10) ELECTRIC SHOWER (40A RCBO — 10MM² CABLE — FOR A 10.5KW SHOWER). (11) IMMERSION HEATER (TYPICALLY A 16A RADIAL ON A TIME CLOCK — 2.5MM² CABLE). (12) ELECTRIC VEHICLE CHARGER PROVISION (32A MCBO/RCBO — 6MM² TWIN AND EARTH — PRE-INSTALLED CABLE RUN FROM CONSUMER UNIT TO THE PLANNED EV CHARGER LOCATION — EVEN IF THE CHARGER IS NOT FITTED AT THE TIME OF REWIRE — THE PRE-INSTALLATION OF THE EV CIRCUIT CABLE DURING THE REWIRE IS SIGNIFICANTLY CHEAPER THAN A SEPARATE INSTALLATION LATER). OUTDOOR SOCKET CIRCUIT (13A FUSED SPUR OR 13A RADIAL — RCD PROTECTED — FOR GARDEN SOCKETS).

THE 18TH EDITION BS 7671 INTRODUCED SEVERAL IMPORTANT NEW REQUIREMENTS FOR EARTHING, BONDING, AND SURGE PROTECTION THAT MUST BE ADDRESSED IN A FULL HOUSE REWIRE FOR A LONDON VICTORIAN TERRACE.

EARTHING ARRANGEMENT IN A LONDON VICTORIAN TERRACE: THE EARTHING ARRANGEMENT FOR A DOMESTIC PROPERTY IN LONDON IS TYPICALLY TN-S (PROTECTIVE MULTIPLE EARTHING — PME — THE NEUTRAL IS COMBINED WITH THE EARTH CONDUCTOR IN THE DISTRIBUTION NETWORK — UK POWER NETWORKS IN LONDON) OR TN-C-S (PME — PROTECTIVE MULTIPLE EARTHING): THE EARTH CONDUCTOR FROM THE ELECTRICITY NETWORK COMPANY (DNO — UK POWER NETWORKS IN LONDON) IS CONNECTED TO THE MAIN EARTH TERMINAL (MET — MAIN EARTHING TERMINAL — THE POINT WHERE THE INSTALLATION'S EARTH IS CONNECTED TO THE DNO EARTH). THE MET IS LOCATED AT THE CONSUMER UNIT. THE EARTHING CONDUCTOR FROM THE METER TO THE MET IS A 16MM² OR 25MM² SINGLE CORE GREEN AND YELLOW INSULATED CONDUCTOR (TYPICALLY RUNNING FROM THE DNO METER/CUT-OUT TO THE CONSUMER UNIT MET). MAIN EQUIPOTENTIAL BONDING (ALSO KNOWN AS MAIN BONDING): BS 7671 CHAPTER 54 REQUIRES THAT THE MAIN METALLIC SERVICES ENTERING THE BUILDING (GAS PIPEWORK — AT THE GAS METER OR AT THE INCOMING GAS PIPE BEFORE IT ENTERS THE BUILDING; AND WATER SUPPLY PIPE — AT THE STOP COCK OR WITHIN 600MM OF THE POINT OF ENTRY INTO THE BUILDING) ARE BONDED TO THE MET WITH A 10MM² MAIN BONDING CONDUCTOR (GREEN AND YELLOW INSULATED). FAILURE TO PROVIDE MAIN BONDING IS A C2 CODE ON AN EICR AND IS A SERIOUS SAFETY DEFICIENCY — PARTICULARLY IN A LONDON VICTORIAN TERRACE WHERE THE GAS METER IS OFTEN IN THE UNDER-STAIRS CUPBOARD AND THE MAIN BONDING CONDUCTOR IS FREQUENTLY ABSENT IN OLDER INSTALLATIONS.

SURGE PROTECTIVE DEVICE (SPD — REQUIRED UNDER 18TH EDITION BS 7671 SECTION 443 FOR NEW INSTALLATIONS WHERE THE LOSS OF EQUIPMENT DUE TO A TRANSIENT OVERVOLTAGE WOULD CAUSE INJURY OR SEVERE DISRUPTION): THE 18TH EDITION (2018) MADE SPD INSTALLATION MANDATORY WHERE A RISK ASSESSMENT DETERMINES THAT TRANSIENT OVERVOLTAGES COULD CAUSE DANGER (SECTION 443.4 — RISK ASSESSMENT GUIDANCE). FOR A LONDON VICTORIAN TERRACE WITH A MODERN TELEVISION, COMPUTER EQUIPMENT, AND SMART HOME DEVICES: THE STANDARD INTERPRETATION IS THAT AN SPD SHOULD BE FITTED. THE SPD IS TYPICALLY A TYPE 2 SPD (100KA 8/20 WAVEFORM — THE STANDARD DOMESTIC SPD) FITTED IN THE CONSUMER UNIT (HAGER VZSPH — OR EQUIVALENT FROM SCHNEIDER OR EATON). PRICE (SPD SUPPLY): £20-40. THE ADDITIONAL COST OF FITTING AN SPD IN THE CONSUMER UNIT AT THE TIME OF A REWIRE IS VERY SMALL — IT SHOULD ALWAYS BE INCLUDED.

ELECTRICAL INSTALLATION WORK IN A LONDON VICTORIAN TERRACE IS NOTIFIABLE UNDER PART P OF THE BUILDING REGULATIONS (ELECTRICAL SAFETY — DWELLINGS) WHENEVER THE WORK INVOLVES: A NEW CIRCUIT FROM THE CONSUMER UNIT; ANY WORK IN A SPECIAL LOCATION (KITCHEN, BATHROOM, GARDEN — ZONES DEFINED IN BS 7671 PART 6); WORK THAT IS NOT CLASSIFIED AS MINOR WORKS (MINOR WORKS INCLUDE REPLACEMENT OF LIGHT SWITCHES, SOCKET OUTLETS, AND LUMINAIRES ON AN EXISTING CIRCUIT — THESE ARE NOT NOTIFIABLE).

FOR A FULL HOUSE REWIRE: ALL WORK IS NOTIFIABLE — BECAUSE A FULL REWIRE INVOLVES NEW CIRCUITS, CONSUMER UNIT REPLACEMENT, AND WORK IN SPECIAL LOCATIONS. THE INSTALLER MUST EITHER: BE REGISTERED UNDER A PART P APPROVED COMPETENT PERSON SCHEME — NICEIC DOMESTIC INSTALLER (NICEIC — NATIONAL INSPECTION COUNCIL FOR ELECTRICAL INSTALLATION CONTRACTING — THE LARGEST PART P SCHEME IN THE UK — NICEIC DOMESTIC INSTALLERS ARE ASSESSED ANNUALLY FOR TECHNICAL COMPETENCE AND WORK QUALITY); OR BE AN ELECSA APPROVED INSTALLER; OR BE AN NAPIT REGISTERED MEMBER — AND SELF-CERTIFY THE INSTALLATION (ISSUING AN ELECTRICAL INSTALLATION CERTIFICATE — EIC — AND NOTIFYING THE CERTIFICATE TO THE LOCAL AUTHORITY THROUGH THE SCHEME). OR NOTIFY BUILDING CONTROL BEFORE STARTING WORK AND HAVE BUILDING CONTROL INSPECT THE INSTALLATION BEFORE PLASTERING AND UPON COMPLETION (THIS ROUTE IS SLOWER AND MORE EXPENSIVE AND IS NOT USED FOR STANDARD FULL HOUSE REWIRES). DOCUMENTS ISSUED ON COMPLETION: ELECTRICAL INSTALLATION CERTIFICATE (EIC — SIGNED BY THE DESIGNER, INSPECTOR, AND TESTER OF THE INSTALLATION — IN PRACTICE ALL THE SAME NICEIC REGISTERED ELECTRICIAN FOR A SMALL FIRM DOING A DOMESTIC REWIRE); AND PART P NOTIFICATION CONFIRMATION (THE NOTICE FROM THE COMPETENT PERSON SCHEME TO THE LOCAL AUTHORITY THAT THE INSTALLATION HAS BEEN COMPLETED AND CERTIFIED — RETAINED IN THE PROPERTY RECORDS).

A FULL HOUSE REWIRE FOR A LONDON VICTORIAN TERRACE (2-3 BEDROOMS — 2 STOREYS — REAR ADDITION — 12-16 CIRCUITS — ALL CABLING FIRST-FIX DURING RENOVATION WHEN CEILINGS AND WALLS ARE OPEN) FOLLOWS A TWO-STAGE PROGRAMME: FIRST FIX (CABLES INSTALLED) AND SECOND FIX (CONSUMER UNIT CONNECTIONS, FITTINGS, TESTING, AND CERTIFICATION).

FIRST FIX (INSTALLED DURING RENOVATION — BEFORE PLASTERING): THE ELECTRICIANS INSTALL ALL CABLE ROUTES (CHASED INTO BRICK WALLS OR RUN THROUGH CEILING VOIDS) — FIX ALL BACK BOXES FOR SOCKETS AND SWITCHES — FIX ALL CEILING ROSE POSITIONS AND DOWNLIGHT VOID BRACKETS — INSTALL THE CONSUMER UNIT ENCLOSURE AND ALL CABLE ENTRIES. TIMING: TYPICALLY 2-4 DAYS FOR 2 ELECTRICIANS (BASED ON A STANDARD VICTORIAN TERRACE 2-3 BEDROOM — 12-16 CIRCUITS). THIS OCCURS BEFORE PLASTERING — THE PLASTERER PLASTERS OVER THE BACK BOXES AND FLUSH CABLE RUNS.

SECOND FIX (AFTER DECORATION OR NEAR-COMPLETION): THE ELECTRICIANS RETURN TO: CONNECT ALL CABLES TO THE CONSUMER UNIT. INSTALL ALL SOCKETS, SWITCHES, CEILING ROSES, AND LIGHT FITTINGS. TEST THE COMPLETE INSTALLATION (INSULATION RESISTANCE, CONTINUITY, EARTH FAULT LOOP IMPEDANCE, AND RCD TESTS — AS REQUIRED BY BS 7671 CHAPTER 61). ISSUE THE ELECTRICAL INSTALLATION CERTIFICATE (EIC). TIMING: TYPICALLY 2-3 DAYS FOR 2 ELECTRICIANS.

FULL HOUSE REWIRE COSTS IN LONDON (2025 — NICEIC DOMESTIC INSTALLER — SUPPLY AND FIT — INCLUDING LABOUR, CONSUMER UNIT, CABLE, BACK BOXES, SOCKETS, SWITCHES, AND EIC/PART P NOTIFICATION): STANDARD VICTORIAN TERRACE 2-BEDROOM (12 CIRCUITS — HAGER DUAL-RCD BOARD — STANDARD SOCKETS AND SWITCHES): £3,500-5,500 (SUPPLY AND FIT — FIRST AND SECOND FIX). STANDARD VICTORIAN TERRACE 3-BEDROOM (14-16 CIRCUITS — SCHNEIDER RESI9 ALL-RCBO BOARD — CHROME SOCKETS AND SWITCHES): £4,500-7,000. UPGRADE COSTS: SCHNEIDER RESI9 ALL-RCBO BOARD VS HAGER DUAL-RCD: ADD £80-200. EV CHARGER PROVISION CIRCUIT (PRE-INSTALLED 6MM² CABLE FROM CU TO EV CHARGER LOCATION DURING REWIRE — BEFORE PLASTERING — THE CHEAPEST TIME TO RUN THE CABLE): ADD £80-150 (JUST THE CABLE RUN — CHARGER FITTED SEPARATELY LATER). SPD (HAGER VZSPH OR EQUIVALENT TYPE 2 SPD): ADD £20-40 (SUPPLY AND FIT DURING REWIRE). NOTE: IF THE REWIRE IS DONE WITH WALLS AND CEILINGS CLOSED (SURFACE REWIRE — NOT DURING RENOVATION): ADD 30-50% TO LABOUR COST FOR THE ADDITIONAL TIME REQUIRED TO FEED CABLES THROUGH CLOSED CEILINGS AND WALLS — AND ALLOWANCE FOR MAKING GOOD (REPLASTERING CHANNELS) AFTER CABLING.