How to Replace a Light Switch UK: Step-by-Step Guide

Swapping a tired white plastic switch for a brushed steel or matt black plate is one of the quickest upgrades a room can get. This guide walks through replacing a like-for-like light switch safely, what the wires mean, and when to call a qualified electrician.

Safety first: Always isolate the lighting circuit at the consumer unit and prove it dead with a voltage tester before touching any terminal. In England and Wales, like-for-like replacement is usually non-notifiable under Part P, but all work must comply with BS 7671. If you are unsure at any point, stop and use a qualified electrician.

What you'll need

  • Replacement switch — see our light switches range (check gangs and 1-way/2-way match your existing switch)
  • Insulated flat and Phillips screwdrivers
  • Voltage tester / approved test lamp
  • Small flat screwdriver for terminal screws

Wiring diagram: 1-way light switch (UK colours)

Consumerunit(lighting MCB)1-gang switchCOML1Light fittingPermanent live — brownSwitched live — brown (sleeved)Neutral — blue (direct to light)Earth (green/yellow) — to back box & metal plate
Schematic only — conductor routes vary (loop-in at rose or at switch). Older cables: red = live, black = neutral; sleeve the switched black brown.

Step-by-step: replacing a light switch

  1. Turn off the circuit. Switch off the lighting MCB at the consumer unit and lock it off or tape it. Confirm the light no longer works.
  2. Prove dead. Unscrew the faceplate, ease it forward and test between all terminals and earth with a voltage tester.
  3. Photograph the wiring. Before disconnecting anything, take a photo showing which conductor sits in which terminal (COM, L1, L2).
  4. Disconnect the conductors. Loosen each terminal screw and note any sleeving. In older installs the switched live may be a blue or black core with (or missing) brown sleeving — sleeve it if absent.
  5. Connect the new switch. Match each conductor to the same terminal markings on the new plate. Connect the circuit earth to the back box earth terminal; metal plates also need the plate earth connected.
  6. Fit and test. Screw the plate back without trapping cables, restore power and test operation.

Common issues

  • The switch works upside down — swap the conductors in L1 and L2.
  • Two switches control one light — that's two-way switching; read our two-way switching guide and buy a 2-way switch (all our BG switches are 2-way capable, so they work in 1-way circuits too).
  • Shallow back box — screwless and metal plates often need 25mm+ depth. See our back box guide.
  • Dimmer instead of a plate switch? Check LED compatibility in our dimmer switch guide, then browse dimmer switches.

Choosing the replacement

If you're upgrading looks as well as function, BG's ranges fit standard UK back boxes: Nexus Metal (raised plate), Nexus Screwless (flat, clip-on front) and Evolve (slim edge-to-edge). See our light switch buying guide for gangs, ways and finishes.

FAQs

Do I need an electrician to change a light switch in the UK?

Like-for-like replacement is generally permitted DIY work in England and Wales and is non-notifiable, but it must be done competently to BS 7671. In Scotland similar rules apply for minor works. If wiring looks damaged, or you find more cables than you expect, use a qualified electrician.

What do COM, L1 and L2 mean?

They're the switch terminals: COM is common, L1 and L2 are the switched outputs. A 1-way circuit uses COM and L1; two-way circuits use all three plus strappers between switches.

Can I fit a metal switch where a plastic one was?

Yes, provided the circuit has an earth (CPC) and you connect it to both the back box and the metal plate's earth terminal.