Zone 0 is the interior of the bath tub or shower basin. Zone 1 runs to the higher of 2.25 m or the highest fixed shower head. Zone 2 is the 0.60 m strip beyond it. This guide gives the boundaries, the IP ratings, the equipment permitted in each zone and the regulation numbers behind them.
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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.
The short answer
Zone 0 is the interior of the bath tub or shower basin and needs IPX7 with SELV at no more than 12 V AC RMS or 30 V ripple-free DC. Zone 1 surrounds the bath or basin up to the higher of 2.25 m or the highest fixed shower head. Zone 2 is the 0.60 m strip beyond it. Both need IPX4.
Section 701 also requires 30 mA RCD additional protection for low voltage circuits serving the location and for circuits passing through zones 1 and 2 (Reg 701.411.3.3), and prohibits socket-outlets within 2.50 m horizontally of the Zone 1 boundary apart from SELV socket-outlets and shaver supply units to BS EN 61558-2-5 (Reg 701.512.3).
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01 · BS 7671 Guide
BS 7671 Section 701 applies to locations containing a fixed bath (bath tub) or shower and to the surrounding zones. It does not apply to emergency facilities such as emergency showers used in industrial areas or laboratories (Reg 701.1). The table below is the whole zone system on one screen; the sections that follow give the detail behind each row.
| Zone | Extent | Minimum IP | Headline restriction |
|---|---|---|---|
| Zone 0 | Interior of the bath tub or shower basin | IPX7 | Fixed, permanently connected SELV equipment only — 12 V AC RMS / 30 V ripple-free DC. No switchgear or accessories. |
| Zone 1 | Vertical surface circumscribing the bath or basin, floor up to the higher of 2.25 m or the highest fixed shower head | IPX4 | Only the fixed equipment listed in Reg 701.55. Switches only on SELV circuits at 12 V AC RMS / 30 V ripple-free DC. |
| Zone 2 | 0.60 m beyond the Zone 1 boundary, over the same height | IPX4 | No switchgear, accessories incorporating switches or socket-outlets, except SELV and shaver supply units to BS EN 61558-2-5. |
| Outside the zones | Beyond Zone 2, or above the zone height | None stated | Socket-outlets still prohibited within 2.50 m horizontally of the Zone 1 boundary (Reg 701.512.3). |
Two rules cut across every zone. Regulation 701.512.2 raises the minimum to IPX5 for equipment exposed to water jets, for example for cleaning purposes. And Regulation 701.411.3.3 requires 30 mA RCD additional protection for low voltage circuits serving the location as well as circuits that merely pass through zones 1 and/or 2.
Section 701 also rules out three protective measures outright: obstacles and placing out of reach (Reg 701.410.3.5), and non-conducting location and earth-free local equipotential bonding (Reg 701.410.3.6). Protection by electrical separation is allowed, but only for a circuit supplying one item of current-using equipment or one single socket-outlet (Reg 701.413).
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02 · BS 7671 Guide
Zone dimensions are measured from the interior of the bath tub or shower basin outwards, and from finished floor level upwards. Get the boundary wrong and every equipment decision downstream of it is wrong too, so it is worth measuring rather than eyeballing.
Vertical limits measured from finished floor level (BS 7671 Regs 701.32.2 to 701.32.4)
Schematic only. Where the highest fixed shower head or water outlet sits above 2.25 m, that higher plane becomes the top of zones 1 and 2.
Regulations 701.32.3(a) and 701.32.4(a) both set the top of the zone at the finished floor level up to the horizontal plane corresponding to the highest fixed shower head or water outlet, or the plane 2.25 m above finished floor level — whichever is higher. A drencher head at 2.4 m therefore lifts the top of Zone 1 and Zone 2 to 2.4 m, and a fitting that would have been outside the zones is now inside them.
Where a shower has no basin, Zone 1 is bounded laterally by the vertical surface 1.20 m from the centre point of the fixed water outlet on the wall or ceiling (Reg 701.32.3(b)(ii)), and there is no Zone 2 — the enlarged Zone 1 replaces it (Reg 701.32.4). Zone 0 in that arrangement is 0.10 m high with the same horizontal extent as Zone 1 (Reg 701.32.2). The 1.20 m figure does not apply to a bath or a shower tray; for those, Zone 1 is bounded by the vertical surface circumscribing the bath tub or basin.
The space under the bath tub or shower basin is Zone 1. If that space is only accessible with a tool, it is considered to be outside the zones (Reg 701.32.3). A screwed or clipped bath panel that comes away by hand does not buy you the exemption.
Ceilings, walls, doors, floors and fixed partitions may be taken into account where they effectively limit the extent of the location and its zones. Where a fixed partition is smaller than the relevant zone — Reg 701.32.1 gives the example of a partition lower than 2.25 m — the minimum distance in the horizontal and vertical directions must be taken into account, so the zone is measured around the partition rather than stopping at it. For equipment set into a wall or ceiling that limits a zone but forms part of that surface, the requirements for the zone apply.
03 · BS 7671 Guide
Zone 0 is the interior of the bath tub or shower basin (Reg 701.32.2) — the space the water occupies and where a person is in direct contact with it. It carries the tightest requirements in the whole of Section 701.
In domestic practice Zone 0 is rarely a design problem, because very little is ever installed inside a bath or shower basin. The main Zone 0 product is purpose-made in-bath LED lighting. A fitting inside a shower enclosure but above the tray is in Zone 1, not Zone 0 — check which one you are actually in before selecting the product.
04 · BS 7671 Guide
Zone 1 is bounded laterally by the vertical surface circumscribing the bath tub or shower basin, and vertically by finished floor level up to the higher of 2.25 m or the plane of the highest fixed shower head or water outlet (Reg 701.32.3). It excludes Zone 0. Minimum degree of protection is IPX4 (Reg 701.512.2).
Regulation 701.55 gives a closed list. Only the following fixed and permanently connected current-using equipment may be installed in Zone 1, and only where it is suitable for Zone 1 according to the manufacturer’s instructions.
| Reg 701.55 | Permitted in Zone 1 | Notes |
|---|---|---|
| (d) | Whirlpool units | Fixed and permanently connected |
| (e) | Electric showers | Fixed and permanently connected |
| (f) | Shower pumps | Fixed and permanently connected |
| (g) | SELV or PELV equipment | Not exceeding 25 V AC RMS or 60 V ripple-free DC, safety source outside zones 0, 1 and 2 |
| (h) | Ventilation equipment | Extract fans rated for the zone |
| (i) | Towel rails | Expressly permitted in Zone 1 |
| (j) | Water heating appliances | Fixed and permanently connected |
| (k) | Luminaires | IPX4 minimum; IP65 downlighters are common practice |
Anything not on that list has no place in Zone 1. Note in particular that the SELV/PELV limit for current-using equipment in Zone 1 is 25 V AC RMS or 60 V ripple-free DC, which is a different figure from the 12 V AC RMS / 30 V ripple-free DC limit that applies to Zone 0 equipment and to Zone 1 switches.
Only switches of SELV circuits at a nominal voltage not exceeding 12 V AC RMS or 30 V ripple-free DC may be installed, with the safety source outside zones 0, 1 and 2. Every other switch, accessory and socket-outlet is prohibited.
Two exclusions sit outside that prohibition entirely: switches and controls incorporated in fixed current-using equipment suitable for use in that zone, and the insulating pull cords of cord-operated switches. The pull cord of a ceiling switch may therefore hang into Zone 1 — it is the switch body that has to be sited acceptably.
A ceiling above 2.25 m puts recessed downlighters outside the zones, but only if no fixed shower head or water outlet sits higher than they do. Where the ceiling is at or below the zone height, a luminaire directly over the bath is in Zone 1 and must be at least IPX4.
05 · BS 7671 Guide
Zone 2 is bounded by the vertical surface at the Zone 1 boundary and the parallel vertical surface 0.60 m from it, over the same height as Zone 1 (Reg 701.32.4). In a typical bathroom that strip takes in the washbasin, the mirror and often the towel rail. Minimum degree of protection is IPX4 (Reg 701.512.2). Remember that a shower without a basin has no Zone 2 at all.
Regulation 701.55 restricts current-using equipment in zones 0 and 1 only, so in Zone 2 any equipment suitable for the location may be used provided it meets the IP requirement. Switchgear and accessories are where Zone 2 bites.
Switchgear, accessories incorporating switches and socket-outlets must not be installed in Zone 2, with two exceptions:
Except for SELV socket-outlets complying with Section 414 and shaver supply units complying with BS EN 61558-2-5, socket-outlets are prohibited within 2.50 m horizontally of the boundary of Zone 1. That distance is measured from the Zone 1 boundary, not from Zone 2, and it applies irrespective of mounting height — so in most bathrooms a 13 A socket is non-compliant anywhere in the room.
Regulation 701.512.2 states that the IPX4 requirement does not apply to shaver supply units complying with BS EN 61558-2-5 installed in Zone 2 and located where direct spray from showers is unlikely. Where direct spray is possible, IPX4 still applies.
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06 · BS 7671 Guide
Additional protection by one or more RCDs having the characteristics specified in Reg 415.1.1 — a rated residual operating current not exceeding 30 mA — must be provided for low voltage circuits:
Limb (b) is the one that gets missed. A circuit that merely runs through Zone 1 or Zone 2 on its way to a bedroom needs 30 mA RCD protection even though nothing in the bathroom is fed from it. The regulation’s note points to Regs 314.1(d) and 531.3.2 on avoiding unwanted tripping — the practical answer is usually an RCBO per circuit rather than everything on one RCD.
A separate and wider requirement sits in Chapter 41: Regulation 411.3.4 requires additional protection by a 30 mA RCD for AC final circuits supplying luminaires within domestic (household) premises. It is not a Section 701 measure and it is not limited to bathrooms — but when you add a bathroom light to an existing lighting circuit, both requirements have to be satisfied.
Local supplementary bonding to Reg 415.2 must connect together the terminals of the protective conductor of each circuit supplying Class I and Class II equipment to the accessible extraneous-conductive-parts within the room, including:
The bonding may be installed inside or outside the room, preferably close to the point at which the extraneous-conductive-parts enter it.
Supplementary bonding may be omitted only where the location is in a building with a protective equipotential bonding system in accordance with Reg 411.3.1.2 and all three of these conditions are met: (d) all final circuits of the location comply with the requirements for automatic disconnection according to Reg 411.3.2; (e) all final circuits of the location have additional protection by means of an RCD in accordance with Reg 415.1.1; and (f) all extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding according to Reg 411.3.1.2. Where main protective bonding is missing or unproven, supplementary bonding cannot be omitted however good the RCD protection is. Reg 415.2.2 gives the test used to assess condition (f) where necessary.
07 · BS 7671 Guide
Bathrooms are among the most frequently coded areas on an EICR. These are the errors that come up again and again.
08 · BS 7671 Guide
The first job on any bathroom is to establish the zone boundaries for that specific room — measure to the highest fixed water outlet, decide whether there is a basin, and only then choose equipment. Small bathrooms often sit entirely inside the 2.50 m socket exclusion; larger ones have real space outside the zones.
Issue your Electrical Installation Certificate or a Minor Works Certificate from your phone. Bathroom work in dwellings is notifiable under Part P except for like-for-like replacement, so the paperwork has to follow the job.
Use the cable sizing calculator to size electric shower and towel rail circuits against the actual installation method, grouping and ambient temperature rather than a rule of thumb.
Reg 701.411.3.3 covers circuits serving the location and circuits passing through zones 1 and 2. Reg 411.3.4 separately requires 30 mA RCD additional protection for AC final circuits supplying luminaires within domestic premises. A consumer unit with an unprotected lighting way will not satisfy either once a bathroom light is added to it.
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