United Kingdom · Wiring Regulations examHow big are the bathroom zones in the 18th Edition?
| Zone | How far it reaches | How high |
|---|---|---|
| Zone 1 | The vertical surface around the bath tub or shower basin. For a shower without a basin, 1.20 m from the centre of the fixed water outlet | To the highest fixed shower head or water outlet, or 2.25 m above the finished floor, whichever is higher |
| Zone 2 | From the edge of zone 1 to a parallel vertical surface 0.6 m further out | The same as zone 1 |
Ceilings, walls, doors, floors and fixed partitions can be taken into account where they effectively limit a zone.
These sizes come from the IET's article on Section 701, Locations containing a bath or shower, written for the 17th Edition. Check them against Section 701 in your Amendment 4 book.
What can go in each zone
- Electrical equipment in zones 1 and 2 needs at least IPX4, or IPX5 where water jets are likely to be used for cleaning.
- A 230 V light fitting above the bath or shower, in zone 1, is allowed if it's at least IPX4.
- A suitable 230 V extractor fan can go in zone 1 or 2 at IPX4 or better. In a bathroom without a window, a fan on the lighting circuit should have its own isolation, and a fan with an overrun needs a triple-pole isolator outside zones 0, 1 and 2.
- Plate switches go outside the zones. Cord-operated switches can be used in zones 1 and 2.
- A shaver supply unit to BS EN 61558‑2‑5 is allowed in zone 2, where direct spray from showers is unlikely.
- 230 V 13 A socket-outlets are allowed only 3 m or more horizontally from the boundary of zone 1.
Washing machines and tumble dryers can go in a bathroom if they're supplied from a switched fused connection unit outside the zones, protected by a 30 mA RCD, and the manufacturer allows it.
RCDs and supplementary bonding in bathrooms
Every circuit in the room needs additional protection by an RCD (Regulation 701.411.3.3). The IET's Section 701 article says that means 30 mA or less on all circuits, including lighting, electric showers and heated towel rails.
Supplementary bonding can be left out where the building has main protective bonding and all three of these are true (Regulation 701.415.2):
- Every final circuit in the room meets the automatic disconnection rules of Regulation 411.3.2.
- Every final circuit in the room has that RCD protection.
- Every extraneous-conductive-part in the room is effectively connected to the protective bonding.
Bathrooms and Part P
A room with a bath or shower is a special location, and installing a shower is notifiable work under Part P of the Building Regulations. The IET says a plumber is unlikely to be competent to replace an electric shower unless specifically trained and experienced.
Sources: IET · IET Wiring Matters and 1 more. Checked October 2026.
- IET: Section 701, Locations containing a bath or shower (Geoff Cronshaw, written for BS 7671:2008, undated) ↗
- IET Wiring Matters: BS 7671:2018 frequently asked questions (September 2019) ↗
- IET: General FAQs on BS 7671 ↗
Rules and fees can change, so check the official site before your test.
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