Bathrooms are special locations under BS 7671. Zone 0, Zone 1, and Zone 2 each have different requirements for what equipment can be installed and what IP rating is needed. All bathroom electrical work is notifiable under Part P. This guide explains everything.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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BS 7671:2018+A4:2026 Section 701 defines specific zones within a bathroom that determine what electrical equipment can be installed and what level of protection is required. These zones exist because bathrooms present a higher risk of electric shock — water reduces skin resistance, and a person in a bath or shower has a direct path to earth through the water and plumbing.
The zones are measured from the bath, shower tray, or shower head position. Understanding them is essential for any electrician carrying out bathroom installations, and for inspectors assessing existing bathroom wiring during an EICR.
Key principle: The closer the equipment is to the water source, the higher the level of protection required. Zone 0 has the strictest requirements; areas outside the zones have the least restrictions.
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Zone 0 is the interior of the bath tub or shower tray. It is the area that can contain water during normal use.
In practice, Zone 0 in a domestic bathroom is usually empty of electrical equipment. The key point is that nothing operating at mains voltage is permitted within the bath or shower tray.
Zone 1 extends vertically from the finished floor level (or the top of the bath/shower tray) to a height of 2.25 metres above the floor. Horizontally, it covers the area directly above the bath or shower tray. For a shower without a tray (such as a wet room), Zone 1 extends to 1.2 metres from the shower head fixing point.
Zone 1 is where most bathroom ceiling lights are located. The light fitting must be rated IPX4 minimum — IP44 or IP65 fittings are the standard choices. Electric showers are also in Zone 1 and must be connected via a fused connection unit or dedicated circuit with the switch located outside the zones.
SELV/PELV voltage limits by zone (Reg 701.55): Zone 0 — maximum 12V AC RMS or 30V ripple-free DC. Zone 1 — maximum 25V AC RMS or 60V ripple-free DC (SELV or PELV). In both zones the safety source must be located outside Zones 0, 1 and 2. These limits matter for low-voltage lighting design — a 12V AC transformer serving Zone 0 downlights must sit outside all three zones, even if that means locating it in the ceiling void above Zone 2.
Zone 2 extends 0.6 metres horizontally beyond the edge of Zone 1, and vertically from the floor to 2.25 metres. It also includes the area above the bath/shower that is above 2.25 metres but within the horizontal extent of Zone 1 (the ceiling void area directly above the bath).
Zone 2 is where bathroom mirrors with integrated lighting, shaver sockets, and some extractor fans are typically located. The 0.6-metre dimension is measured horizontally from the edge of the bath or shower tray — use a tape measure to establish the exact boundary.
The area outside Zone 0, Zone 1, and Zone 2 has fewer restrictions, but bathrooms are still considered special locations under BS 7671. The key rules outside the zones:
On-site gotcha — space under the bath (Reg 701.32.3): The space beneath a bath panel is classified as Zone 1, not outside the zones — unless that space is only accessible with a tool (e.g. screws holding the panel). Where the bath panel is removable by hand, any wiring, fused connection units, or isolators in that void must meet Zone 1 requirements (IPX4, no socket outlets). This is a commonly missed item on EICRs.
In many small UK bathrooms, the entire room falls within Zone 1 and Zone 2, with no area "outside the zones." In larger bathrooms, there may be a small area outside the zones — typically at the far end of the room from the bath/shower.
Regulation 701.415.2 requires local supplementary protective equipotential bonding in rooms containing a bath or shower. This connects together the terminals of the protective conductor of each circuit supplying Class I and Class II equipment to all accessible extraneous-conductive-parts within the room.
Three-condition test for omitting supplementary bonding
Supplementary bonding may be omitted where the building already has a protective equipotential bonding system per Reg 411.3.1.2 AND all three of the following conditions are met: (d) all final circuits in the bathroom comply with automatic disconnection requirements (Reg 411.3.2); (e) all final circuits have additional 30mA RCD protection (Reg 415.1.1); (f) all extraneous-conductive-parts in the location are effectively connected to the main protective equipotential bonding. All three conditions must be satisfied — meeting only one or two is not sufficient.
Supplementary bonding is one of the most frequently missed items on bathroom EICRs and is an active inspection item on the EIC. When inspecting an existing installation, verify that bonding conductors are present, correctly labelled, and properly terminated.
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The IP (Ingress Protection) code consists of two digits. The first digit indicates protection against solid objects (0 to 6). The second digit indicates protection against water (0 to 9). When an "X" replaces a digit (e.g., IPX4), it means that protection level was not tested for — it does not mean zero protection.
Building Regulations Approved Document F (Ventilation) requires mechanical extract ventilation in bathrooms without an openable window. Even in bathrooms with a window, a fan is recommended to control moisture and prevent condensation and mould.
An electric shower requires a dedicated radial circuit from the consumer unit. It is one of the highest-rated fixed appliances in a domestic installation, typically drawing 35A to 48A.
The shower circuit must be RCD-protected (30mA) in accordance with BS 7671 Regulation 701.411.3.3. The shower unit must be connected via a double-pole isolator switch located outside Zone 1 and Zone 2 — typically a 45A ceiling pull-cord switch with a neon indicator. The cable must be routed to avoid Zone 1 where possible, or if it passes through Zone 1, it must be mechanically protected or installed in a conduit.
Always check the manufacturer's installation instructions for the specific shower model — some high-powered showers (10.8kW and above) require 16mm cable and a 50A protective device.
Part P of the Building Regulations classifies all electrical work in a bathroom as notifiable, regardless of whether it involves a new circuit. This includes:
The electrician must be registered with a competent person scheme to self-certify, or the work must be notified to building control directly. An Electrical Installation Certificate (EIC) is required for new circuits; a Minor Electrical Installation Works Certificate (MEIWC) may be appropriate for like-for-like replacements on existing circuits.
Bathroom electrical work is one of the most common domestic installation tasks, but the zone requirements and Part P notification make it more involved than a standard circuit installation. Elec-Mate streamlines the process:
Select the equipment type and location, and Elec-Mate confirms the IP rating requirement and whether the equipment is permitted in that zone. No more flipping through Section 701 on site.
The EIC includes all Section 701 inspection items pre-populated: supplementary bonding, IP ratings, SELV sources, RCD protection, and zone identification. Voice entry fills in the test results while you work.
Join 1,000+ UK electricians using Elec-Mate for bathroom installation certificates. Zone compliance checking, voice test entry, instant PDF delivery.
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