Cable Types, Sizes & Colour Codes

The most common cable used in UK domestic wiring is Twin & Earth (T&E), also called flat grey cable. It contains three conductors in a flat grey sheath:

Cable Sizes

| Size | Used for | Max current | |------|----------|-------------| | 1mm² | Lighting circuits | 10–15A | | 1.5mm² | Older radials, some spurs | 15–20A | | 2.5mm² | Ring final, radial socket circuits | 20–27A |

Always match the cable size to the MCB rating for that circuit. A 32A ring main needs 2.5mm² T&E.

3-Core T&E

For 2-way switching, you need 3-core T&E. This adds a grey conductor (used as the switch wire). Because grey is normally neutral, any grey conductor used as a live switch wire must be sleeved with brown tape at both ends.

See 2-core vs 3-core T&E — when & why for more detail.