Understanding bathroom electrical zones (BS 7671)

Helpful video reference. Marcus from eFIXX explains bathroom zones in his video "Bathroom Zones Explained — Zones 0, 1 and 2 — IP Ratings and are BS 1363 13A Socket Outlets Allowed". eFIXX is a UK electrical training channel aimed at electricians and electrical apprentices, and Marcus covers the zone boundaries clearly with diagrams. He also addresses the question about 13A sockets directly. Worth watching if you find diagrams easier to follow than text.

1. Zone 0: inside the water

Zone 0 is the interior of the bath tub or shower tray itself. It is the area that is actually submerged when water is present.

Only SELV (separated extra-low voltage, 12 V maximum) equipment may be used here, and that equipment must carry at least an IP67 rating — meaning it is protected against full temporary immersion. Underwater bath lights are the main product designed for Zone 0, and they need a safety extra-low voltage transformer located outside the bathroom entirely.

Almost no homeowner DIY project involves Zone 0. If you are considering it, use a qualified electrician.

2. Zone 1: above the bath, inside the shower

Zone 1 extends:

• Directly above the bath tub from floor level to 2.25 m high.
• Inside the shower cubicle from floor to 2.25 m, regardless of whether the shower has a tray or is a wet room.

Equipment in Zone 1 must be at least IPX4 (splash-proof from any direction) and must be specifically approved for Zone 1 use. In practice this means:

• Ceiling-mounted shower lights directly above the bath or inside the shower must be rated IP44 or better and carry a Zone 1 designation.
• Electric shower units installed on the wall inside the shower zone are designed for Zone 1. The supply cable runs to the unit; no switching is permitted inside Zone 1.
• No switches, socket outlets, or fused spurs are allowed inside Zone 1.

Towel rails positioned inside Zone 1 — which is unusual but possible in small bathrooms — must carry IP44 or better and must still be supplied via an FCU located outside Zone 1.

3. Zone 2 and outside zones

Zone 2 is the area extending 0.6 m horizontally from the edge of the bath or the outside edge of the shower cubicle, from floor level to 2.25 m high. It also includes the area above Zone 1 from 2.25 m up to 3.0 m if within the 0.6 m horizontal distance.

Equipment in Zone 2 must be at least IPX4. In practice:

• Light fittings, extractor fans and shaver sockets in Zone 2 must be splash-proof.
• Heated towel rails positioned in Zone 2 must carry IPX4 and must be connected via an FCU outside Zone 1 (the FCU itself can be in Zone 2 if it carries IPX4).
• Switches for lights and fans may be positioned in Zone 2 if they carry the appropriate IP rating, though placing them just outside the bathroom door avoids the question entirely.

Outside zones means more than 0.6 m horizontally from the bath rim or shower edge, and above 2.25 m if within the 0.6 m distance. Normal rules apply here — standard fittings are permitted, though IPX4 light fittings are still good practice given the general humidity in bathrooms.

4. IP ratings explained

The IP (Ingress Protection) rating is stamped on the product and tells you how well the fitting keeps out particles and water. The format is IP followed by two digits:

• First digit: protection against solid particles. 4 means no object over 1 mm can enter. 5 means dust-protected. 6 means dust-tight.
• Second digit: protection against water. 4 means splash-proof from any direction. 5 means protected against water jets. 7 means protected against temporary immersion.

IPX4 means the first digit is unknown or irrelevant (often because the test was not done), but the fitting is splash-proof. For bathroom fittings, IPX4 is the minimum acceptable in Zones 1 and 2.

Some fittings are marked IP44 — this gives solid and water protection ratings. A fitting marked IP65 would be fully dust-tight and water-jet protected — more than enough for a bathroom, but you would typically only see those in wet rooms or outdoor installations.

5. What is and is not allowed — a quick reference

• Standard 13A socket outlets: Not permitted anywhere in a bathroom, regardless of zone. The only socket allowed is a BS EN 61558 shaver socket with an isolating transformer, which may be installed in Zone 2 or outside zones.
• Light switches: Must be outside Zone 1. Pull-cord switches with non-conductive strings are permitted in Zone 1 and Zone 2. Standard rocker switches should be positioned outside the bathroom or at least outside Zone 2 where possible.
• Extractor fans: The fan body in Zone 1 or Zone 2 must carry IPX4. The switch should be outside Zone 1; a pull cord inside the zone is acceptable. Alternatively, humidistat-controlled fans need no manual switch at all.
• Heated towel rails: Permitted in all zones with the correct IP rating. Must be supplied via a fused connection unit with no removable plug. The FCU must be outside Zone 1.
• Downlights: Must carry the correct IP rating for the zone. In Zone 1, the fitting must be Zone 1 rated. In Zone 2, IPX4 minimum. Bathroom-rated downlights will state their zone suitability in their documentation.

6. Heated towel rails and how they must be connected

An electric heated towel rail is a fixed appliance, not a portable one. It must be permanently connected to a mains supply — not plugged into a socket. The correct method is a fused connection unit (FCU) with a 3 A fuse, connected to a spur from the main ring or a dedicated radial circuit.

The FCU must be located outside Zone 1. In a small bathroom, this often means routing the spur to an FCU on the wall outside the zone boundary, or running it to an FCU in an adjacent cupboard or hallway. A flush-mounted FCU is the neatest solution and keeps the wiring inside the wall.

Some towel rails include a timer or thermostatic controller. These are usually fitted to the rail itself and need no additional switching, but the mains connection method is the same.

7. Part P and getting the paperwork right

Because bathrooms are a special location under Part P Building Regulations, almost all electrical work in a bathroom requires either a registered electrician who is a member of a competent person scheme (such as NICEIC, NAPIT or ELECSA), or a Building Regulations application to the local authority before work starts.

The work that always requires notification includes new circuits, new FCUs for towel rails, new lighting circuits, new extractor fans wired into a mains circuit, and replacement consumer unit protective devices in connection with bathroom work.

What does not require notification is like-for-like replacement of an existing fitting in the same position: swapping one ceiling rose for another, replacing a pull cord with the same pull cord, replacing a shaver socket with the same type. Even then, an EICR at sale time will flag anything that is non-compliant, so it is worth getting it right.

When to call us

Bathroom electrical jobs in Sandwich — whether it is a new towel rail connection, a replacement extractor fan circuit, an extra light fitting, or a full bathroom refurbishment rewire — all need a registered electrician. Richard covers Sandwich and east Kent for exactly this kind of work, and every bathroom job comes with the correct certification.