Extension Rewiring
North London
Building a rear extension, side return, double-storey or garden room? The electrical work has to slot into your build programme — and it has to pass Building Control. We handle the full scope: first-fix coordinated with your builder, second-fix after plaster, all new circuits tested, certified and lodged with Building Control on your behalf.
NICEIC Registered Electrician · Part P & Building Regulations · Building Control Lodgement Included · 5-Star Rated on Google
Extension Wiring Problems We Solve in North London
We coordinate the circuits, first fix, second fix, testing and certification so electrical work does not become the part of the build that causes avoidable delays.
“Will you coordinate with my main contractor?”
Yes — we plan our visits around your build programme, not the other way around. We confirm first-fix and second-fix dates with the main contractor or project manager up front and stick to them. If the build runs ahead or behind, we adjust. We’re used to live sites with bricklayers, plasterers, plumbers and roofers all on the go — we slot in without slowing anyone down.
“Do you handle Building Control notification?”
Yes — as NICEIC-registered electricians we self-certify all new circuit work under Part P of the Building Regulations. We notify Building Control on your behalf and issue you a Building Regulations Electrical Certificate (EIC) on completion. You don’t need a separate inspection or extra fee — the lodgement is part of our scope.
“Do you work first-fix before plasterboard?”
Always. First-fix means cables run, back-boxes set, consumer unit isolated and any new circuit ways prepared — all before the plasterer arrives. Second-fix happens after decoration: sockets, switches, light fittings, appliance connections, then full testing. Two clean visits, programmed with your builder. See House Rewiring North London for a fuller scope when the existing house also needs work.
“Do I need to upgrade my consumer unit?”
Often, but not always. We assess your existing board capacity at survey stage. Many 1990s–2010s consumer units have spare RCBO ways that can take the new extension circuits. Older or full boards need replacing — typically £800–£1,200 added. See Consumer Units North London. We confirm before any work starts.
“Will the electrical work delay my build?”
No — not if it’s scoped properly. First-fix on a standard single-storey rear extension is 1–2 days. Second-fix is half a day to a full day. We book those slots in advance with your contractor, then turn up on the day. Programme delays on extension projects almost always come from late electrical scoping — we book your survey early so we’re ready to first-fix the moment the structure’s up.
“Can my builder’s electrician just do this?”
Only if the notifiable Part P work is completed through a registered competent-person scheme or approved by Building Control. If they’re not, the work has to be inspected and certified by a separate registered electrician or by Local Authority Building Control — both add cost and time. We bring our own NICEIC registration (D609991) to your project so the lodgement runs cleanly. Verify any contractor on the NICEIC register before they start.
What Our Customers Say About Us
Real reviews from homeowners and main contractors across North London. Live Google reviews below — for all 388+ reviews across Google, Checkatrade and MyBuilder, see our testimonials page →
Book Your Free Extension Survey
Tell us about your extension — size, scope and current build stage — and we’ll arrange a free no-obligation site survey. Fixed price quote before any work begins.
NICEIC Registered
All extension wiring by an NICEIC-registered electrician — fully BS 7671 18th Edition (Amd 2) compliant, supplied with the applicable certification and Building Regulations documentation.
Building Control Lodged
We notify Building Control under Part P and issue your Electrical Installation Certificate on completion. No separate inspection, no extra fee — lodgement is part of our scope.
Programme-First
First-fix slot booked before plasterboard, second-fix after decoration. Dates confirmed with your main contractor in advance — we never hold up the build.
From £950
Small extension first + second fix from £950 (2 RCBO circuits, 4 sockets, 1 light & switch — subject to existing CU capacity). Typical kitchen-extension full electrical scope is £1,200–£2,500.
Six Compliance Tests Every Extension Circuit Must Pass
Every new circuit added to your existing installation has to pass six specific tests before Building Control will sign off the extension. Generic electricians cut corners — we don’t. Here’s what every circuit goes through before it’s energised, certified and lodged.
Electrical Installation Certificate (EIC) lodged via Part P
Every new circuit in the extension has to be certified on a full EIC, not a Minor Works form. The certificate must reference the new circuits as additions to the existing installation, list every test result, and be lodged via our NICEIC competent-person scheme. Building Control will not sign the extension off without it. We issue the EIC the day testing completes and lodge it the same week — you get a copy for your build pack.
Continuity testing of the protective conductor
Every new circuit’s circuit protective conductor (CPC) has to be tested for continuity end-to-end and back-bonded to the existing installation’s main earth. We measure resistance at every accessory and at the consumer unit — values logged on the EIC. A discontinuity at the join between new and existing wiring is the most common reason first-time continuity tests fail, especially on properties with older TT or TN-S earthing arrangements.
Insulation resistance — new wiring against existing
Insulation resistance (IR) at 500V DC must read ≥1.0 MΩ on every new circuit, with no breakdown at the join with existing wiring. Old VIR or rubber-sheathed cable nearby will pull readings down — we test before and after connection so any borderline existing circuits are flagged in writing. If readings fail, we don’t energise the circuit. The fix is identified before the plasterer comes back, not after.
RCD/RCBO protection on every new circuit
Under the current edition of BS 7671 (post-2022), every new circuit in a domestic installation — including lighting and fixed-equipment circuits — needs 30mA RCD or RCBO protection. Older boards with only main-switch RCD protection won’t pass for a new extension. We fit individual RCBOs on each new way, or quote a board upgrade where the existing unit can’t take RCBOs. RCD trip times tested and logged on the EIC.
Bonding of new metallic services entering the extension
Per Reg 411.3.1.2, any new metallic gas, water or structural service entering the extension must be main-bonded back to the MET with 10mm² green/yellow earth cable. New steel beams, new copper water feeds, new gas runs to a hob — all bonded. We check the existing main bonding too while we’re there: failed or missing main bonds at the original installation will fail the extension by association, and Building Control will pick it up.
Notification & lodgement within 30 days
Notifiable work under Part P must be notified to Building Control within 30 days of completion via the competent-person scheme. We lodge electronically through NICEIC the same week we test — certificate number issued by Building Control, sent direct to you and the local authority. Without this lodgement, your extension can’t be signed off and the local authority can refuse a completion certificate on the wider build. We track every lodgement to closure.
How We Complete Your Extension Rewire
From first survey to Building Control lodgement — six clean steps, programmed around your build. Most extensions complete across two visits totalling 2–4 days on site.
Site Survey & Programme
We visit while the structure is going up — ideally before plasterboard is ordered. We assess existing consumer unit capacity, confirm circuit count, agree socket and light positions with you, and book first-fix and second-fix dates with your main contractor. Free, no obligation.
Fixed Price Quote
Detailed quote covering all materials, labour, testing, certification and Building Control lodgement. If a consumer unit upgrade is required, it’s priced separately so you see the breakdown. The price we quote is the price you pay — no hourly billing, no surprise extras.
First-Fix Coordinated With Builder
Cables run through new joists, studwork and floor voids before plasterboard. Back-boxes set at agreed heights. New circuits pulled back to the consumer unit and isolated. We work around the bricklayer, plumber and roofer — one day on site, sometimes two for larger extensions.
Plasterboard & Decoration (Builder)
We’re off site while the plasterer, painter and joiner finish. Cables protected behind board, back-boxes flush, no risk of damage. Your contractor calls us back when units, fittings and final decoration are ready for second-fix.
Second-Fix & Connections
Sockets, switches, light fittings, oven and hob connections, extractor, underfloor heating thermostats — all fitted, terminated and energised on the new RCBO ways. We brief you on which switch does what and label the consumer unit so any future electrician picks it up cleanly.
Testing, EIC & Building Control
Full BS 7671 testing on every new circuit: continuity, IR, polarity, earth-fault loop impedance, RCD trip times. Electrical Installation Certificate Issue timescale confirmed, lodged via NICEIC to Building Control within the week. You receive the EIC, test results and Building Control certificate number for your build pack.
Extension Rewiring Pricing
Quick reference for North London extensions. Fixed quotes given after a free site survey — final price depends on size, circuit count and whether a consumer unit upgrade is needed.
- ✓ 2 new RCBO circuits (subject to existing CU capacity)
- ✓ 4 double sockets supplied & fitted
- ✓ 1 ceiling light + 1 switch wired
- ✓ First + second fix, all tested
- ✓ Full EIC & Building Control lodgement
- ★ All new circuits run from board to extension
- ★ Dedicated oven, hob & extractor supplies
- ★ Sockets, lighting, external lights, bifold zone
- ★ Underfloor heating control wiring (if required)
- ★ Full testing, EIC & Building Control lodgement
- ✓ Multiple new circuits across two floors
- ✓ Consumer unit upgrade quoted if needed
- ✓ Smart/AV first-fix wiring (CAT6, HDMI)
- ✓ External lighting & security cabling
- ✓ Full testing, EIC & Building Control lodgement
Professional Extension Rewiring North London — Across All Property Types
From Victorian rear extensions in Crouch End to 1930s side returns in Palmers Green and loft conversions tied to rear extensions in Muswell Hill — every property type has different challenges for extension wiring. Here’s how we handle each.
Swipe to explore all property types
Victorian Rear Extensions
📍 Crouch End, Hornsey, Stoke Newington, Highbury
Original 80–120-year-old wiring still feeding the back of the house. Lath-and-plaster meeting new plasterboard at the join. No spare ways on the existing fuse board. Earthing arrangement often TN-S with corroded sheath bonds.
New circuits run through the extension joists straight back to a board upgrade. We back-bond every new earth to the main earthing terminal and IR-test the new wiring against the existing — any borderline old circuit gets flagged in writing before sign-off.
1930s Side Returns & Semis
📍 Palmers Green, Bounds Green, Arnos Grove, Cockfosters
Most common extension property type in North London. Existing ring main often shared with utility or dining room. Consumer unit may be 1990s/2000s with limited spare RCBO ways. Side return creates long cable runs from the original board.
Dedicated 45A hob supply, separate oven circuit, new sockets ring on its own RCBO. Cable size up-rated where runs are long to avoid voltage drop. Board upgrade to a modern RCBO unit if needed — quoted separately.
Open-Plan Kitchen-Diner Extensions
📍 Muswell Hill, Highgate, Crouch End, Cockfosters
Knock-through plus rear extension — new footprint much bigger than the original wiring planned for. Bifold doors, kitchen island with sockets, integrated lighting zones, induction hob, range cooker. Significant load increase on the existing supply.
Coordinated load design — extension on its own RCBO ways, separate lighting zones for cooking vs dining, island wired with concealed underfloor cable, bifold soffit lighting on its own circuit. See Kitchen Rewiring North London for the appliance-circuit detail.
Loft Conversions & Garden Rooms
📍 Wood Green, Tottenham, Walthamstow, Enfield
Loft tied to a rear extension on the same build. Garden rooms 15–25m from the house needing armoured supply. Restricted cable routing through existing ceiling voids. Some leasehold flats need freeholder consent for the work.
SWA armoured supply for garden rooms with its own RCBO at the main board. Loft circuits run via stairwell void and tied into the rear extension circuits where the wiring runs are shared. Documentation provided for freeholder or managing agent if required. Building Control lodgement covers both works as one notification.
Need an extension wired in your North London property?
Extension Rewiring FAQs for North London Homeowners
Clear answers to the most common questions homeowners and main contractors ask about extension wiring, Building Control, Part P notification and coordinating electrical work with the wider build across North London.
For official guidance, visit Electrical Safety First or read the Building Regulations guidance.
Do I need a Part P notification for extension electrical work?
Yes — all new circuits in a house extension are notifiable under Part P of the Building Regulations. As NICEIC-registered electricians we self-certify and notify Building Control on your behalf, then issue you a Building Regulations Electrical Certificate on completion. You don’t need a separate Building Control submission or extra inspection fee — it’s part of our scope.
What does Building Control actually test on my extension wiring?
Building Control review the certificate we lodge — they don’t physically re-test. The certification has to confirm: continuity of every new protective conductor, insulation resistance ≥1.0 MΩ on every new circuit, polarity, earth-fault loop impedance within limits, and RCD trip times under 300ms at 5×IΔn. Every new circuit must have 30mA RCD or RCBO protection per BS 7671 Amd 2. We test all of this and lodge the results — that’s the audit trail Building Control rely on.
Can my builder’s electrician just do this work?
Only if they’re Part P & Building Regulations through a competent-person scheme like NICEIC, NAPIT, or Stroma. If they’re not, the work has to be inspected by a registered third-party electrician or Local Authority Building Control — both add cost (£200–£500) and time. Always verify your contractor’s registration on the NICEIC register before they touch a cable. Our registration is D609991.
What is first-fix and second-fix electrical work?
First-fix is everything done before plastering — cables run through walls, joists and ceilings, back-boxes set, new circuits pulled back to the consumer unit and isolated. Second-fix is everything after plaster and decoration — sockets, switches, light fittings, appliance connections, then full testing and certification. For an extension, both stages are required. We programme both visits with your main contractor. We use the same first-fix/second-fix coordination on loft conversions.
Will I need a new consumer unit for my extension?
Not always. Many 1990s–2010s North London consumer units have spare RCBO ways for new extension circuits. However, older or full boards, or extensions with significant load (induction hob, underfloor heating, bifold lighting, range cooker) usually need an upgrade. Under BS 7671 Amd 2, every new circuit needs 30mA RCD or RCBO protection — older boards with only main-switch RCD won’t pass. We assess at survey and quote any upgrade upfront (typically £800–£1,200). See Consumer Units North London.
How long does extension electrical work take?
First-fix on a standard single-storey rear extension takes 1–2 days. Second-fix is half a day to a full day depending on circuit count and fittings. Total on-site time is typically 2–4 days, spread across the build programme. Two-storey extensions, those with underfloor heating, AV wiring or large kitchen-diners take longer. We confirm exact dates after the site survey so your builder plans around them.
How much does house extension electrical work cost?
A small extension or garden room with first + second fix starts from £950 — that’s 2 RCBO circuits, 4 sockets, 1 light and switch (subject to existing CU capacity). A typical kitchen-extension full electrical scope is £1,200–£2,500 — first-fix, second-fix, new circuits, oven and hob supplies, lighting, sockets and Building Control lodgement. Larger or multi-storey extensions start from £3,000+. Consumer unit upgrades quoted separately. Fixed price after free site survey.
What electrical circuits does a house extension typically need?
A standard kitchen-diner extension needs: a 32A sockets ring for worktop and general sockets, a 6A lighting circuit, a 32A or 45A hob supply on 6mm² cable, a 16A oven circuit, a 13A FCU for the extractor, plus an underfloor heating circuit if specified. Garden rooms and annexes need an SWA armoured supply, outdoor sockets and external lighting on their own circuits. We plan all circuits at the survey stage.
Can you install underfloor heating controls as part of the extension?
Yes — we work alongside your underfloor heating contractor to install the electrical supply, thermostat wiring and zone controls as part of the first-fix scope. We coordinate with your heating engineer on control locations and ensure all circuits are correctly rated, RCBO-protected and certified. Best confirmed at the survey stage so the work is included in your fixed price quote rather than added later.
What if my existing extension has failed an EICR?
Common with extensions built before Part P (pre-2005) or by non-registered electricians. We attend, identify the failure codes (typically C1/C2 — missing earth bonds, undersized cables, no RCD protection, shared circuits with bathroom or kitchen), and quote a targeted remedial rewire. New circuits replace the failing ones, RCBO protection retro-fitted, full re-test and a fresh EIC. See House Rewire Cost Guide for budget context on remedial scope.
Need an Extension Wired in North London?
Honest, fixed-price quotes after a free extension site survey. NICEIC-registered, fully certified, Building Control lodgement included. Programmed around your build, never holding it up. Covering all 8 boroughs across North London.
