What does second fix electrics include?

Second fix is when the buried cables get connected to something visible: faceplates onto sockets and switches, light fittings hung, the consumer unit completed, then the whole installation tested and certified. It turns a shell with wires poking out of walls into a space with working power.

Do you need a Part P certificate for an extension?

Yes. Notifiable electrical work in a home needs to be signed off under Part P, and your electrician issues an Electrical Installation Certificate (EIC) once testing is complete. Building control will not sign off the extension without it, so the certificate is a hard dependency, not a formality.

Why does the electrical bill come in higher than the quote?

The original quote usually covers standard white accessories on the circuits wired at first fix. Upgraded faceplates, smart devices, outdoor lighting, under-cabinet lighting and any fittings the electrician buys for you are extras that commonly add 50 to 100 percent on top.

What is the difference between first fix and second fix electrics?

First fix is the cabling and back boxes buried before plastering. Second fix is fitting the visible accessories, completing the consumer unit, and testing and certifying the installation after the walls are finished.

How long does second fix electrics take on an extension?

The hands-on work is typically a few days on site, but the invoices often arrive over weeks because accessories, smart devices and snagging items rarely all happen in one clean visit. The certificate normally follows within 30 days.

Back to Kitchen Extension

Phase 7 · Second Fix · Task 02 of 08

Second Fix Electrics: Sockets, Lights, and Final Wiring

What second fix electrics costs for a UK extension (£1,500 – £5,000), why the bill doubles, and how to get your electrical certificate without delays.

11 min readUpdated 2026Free with email

Process flow showing second fix electrics stages from plastering complete through faceplate installation, consumer unit completion, testing, and EIC certificate handover

Prerequisites

Complete these first

Your electrician will quote you a number. You'll pay significantly more than that number. This isn't a scam. It's how second fix electrics works on every extension project, and understanding why is the difference between a budget blowout that blindsides you and one you planned for.

Second fix is when all the cables your electrician buried in the walls during first fix finally get connected to something visible. Faceplates go onto sockets and switches. Light fittings get hung. The consumer unit gets completed, tested, and certified. Your extension goes from a shell with wires poking out of walls to a space with working power.

The work itself takes 3-5 days for a typical extension. But the invoices will arrive over weeks or months, because second fix electrics rarely happens in one clean visit.

What this guide covers

01What's actually in the quote
02The scheduling dance
03What can go wrong
04The consumer unit
05Certification: the paperwork that matters most
06Realistic costs
07Before your electrician starts
08The finish quality your electrician should deliver

Free guide — just enter your email

This guide is free. Enter your email to unlock it instantly. You'll also get notified when new guides are published.

No spam. Unsubscribe anytime.