Zones in Bathrooms: BS 7671 Amendment 2 Explained

Why Bathroom Zones Matter

Bathrooms are one of the highest-risk locations in any electrical installation. People remove their clothes, stand on wet floors and reach for switches with damp hands — all while surrounded by water and earthed metalwork. BS 7671 addresses this in Section 701, “Locations containing a bath or shower”, by dividing the room into zones with progressively relaxing requirements the further you get from the water.

If you are revising for the ECS HS&E test or the AM2, bathroom zones are a perennial favourite for catching candidates out. The recent Amendment 2 to the 18th Edition (the brown book) introduced a small but important change, and the basic drawings on pages 245 and 246 of the regulations can be confusing. This guide breaks the zones down clearly so you can answer with confidence.

“The zones have particular dimensions for the safety of the user.”

Think of the Zones as Boxes

The simplest way to picture bathroom zones is as a set of invisible boxes. One box surrounds the bath itself, and another box extends out from its edge across the floor.

There is a height requirement common to all zones of 2.25 metres. However, if the shower head or another water outlet sits higher than this, the height requirement rises with it. So a tall ceiling-mounted shower will push the zone boundary upwards.

Horizontally, the zones run as follows:

• Zone 0 and Zone 1 — where the bath sits, with the strictest rules
• Zone 2 — a band where the rules relax slightly
• Outside the zones — a further reduction in requirements

Zone 0 and Zone 1

Zone 0 is the space inside the bath — the volume the water occupies, right up to the top of the bath. It is only that space and nothing more.

Zone 1 is the space above and below the bath that is not Zone 0. Crucially, this includes the area underneath the bath — unless something changes that.

“If the bath panel requires a tool — a screwdriver, for example — or a key to remove it, then the space under the bath is classed as being outside the zones and not Zone 1.”

So a panel that lifts off by hand leaves the space beneath it as Zone 1, but a panel secured with screws or a key reclassifies that space as outside the zones.

The Zone 1 border trap

This is where many candidates lose marks. Zone 0 is measured from inside the bath, but the Zone 1 boundary is taken from the outside edge of the bath. With most baths, that difference can be 50 millimetres or more once you account for the thickness of the bath rim. Read every exam question carefully — it matters whether it refers to the inside or the outside edge.

Zone 2 and Outside the Zones

Both Zone 2 and the outside-the-zones area start from the outside edge of Zone 1, not Zone 0.

• Zone 2 extends 0.6 metres horizontally from the edge of Zone 1.
• Outside the zones then runs from that 0.6 metre point out to 2.5 metres, measured along the floor from the bath.

The regulations word this as “2.5 metres from the bath”, which trips people up. Because the first 0.6 metres is Zone 2, the genuinely “outside the zones” band is the space between 0.6 metres and 2.5 metres.

“This is the major change — this used to be up to three metres.”

That reduction from 3 metres to 2.5 metres under Amendment 2 is exactly the kind of detail an examiner will use to catch out anyone revising from older material. And remember: there is no Zone 3. Despite many people still calling the outside-the-zones area “Zone 3”, that terminology was dropped years ago.

Beyond 2.5 metres horizontally, or above 2.25 metres in height, you are into normal territory where the standard wiring regulations apply. Many bathrooms exceed 2.25 metres in height — handy for mounting a ceiling pull switch — but most are small enough that the floor never reaches 2.5 metres from the bath.

IP Ratings and Voltage Limits by Zone

Equipment must be selected to suit the zone it sits in. Here is a summary:

In Zone 1, certain permanently connected items are permitted provided they are correctly IP rated — electric showers and shower pumps, whirlpool units, fans and ventilation equipment, towel rails, water heaters and luminaires.

In Zone 2, shaver sockets must comply with BS EN 61558-2-5 (or equivalent), and you must consider whether direct jets of water from the shower are likely to fall on them. Because 230 V switches and sockets are not permitted in Zone 2, the shower on/off control is often a ceiling-mounted pull cord — the string is not counted as a conductive part.

In the outside the zones area (the old “Zone 3”), most general requirements apply. Fused spurs and switched FCUs are permitted, but 230 V sockets are still not allowed. Only once you are beyond 2.5 metres and above 2.25 metres can 230 V sockets be fitted — and even then they must have 30 mA RCD protection.

RCD Protection and SELV Sources

This is where bathroom rules become non-negotiable, and the logic ties straight back to the Health and Safety at Work etc. Act 1974 duty to protect people from harm:

• All circuits within a bathroom location must have 30 mA RCD protection, except SELV circuits.
• Any circuit passing through Zone 1 or Zone 2 must also have 30 mA RCD protection — even if it supplies nothing inside the zones. If it passes through the zone, it needs the RCD.
• SELV sources — typically a 230 V transformer feeding low-voltage downlights — together with their 230 V cables must be physically located outside the zones. They can sit in the loft or behind a wall, but never inside a zone.

For heating, underfloor and wall heating installations (other than SELV) must be covered by an earthed metallic grid, and the heating cables themselves must have an earthed metallic sheath. The principle running through all of these rules is protecting a vulnerable user from electric shock.

If you want to revise the wider protective measures these zones build on, our Essential Electrical Safety guide for ECS card holders is a useful companion. For the legal framework around domestic work, see Part P Building Regulations Explained, and before working on any bathroom circuit make sure you are confident with safe isolation of a consumer unit.

Quick Revision Checklist

Before your test, make sure you can recall:

1. There are four areas: Zone 0, Zone 1, Zone 2 and outside the zones — and no Zone 3.
2. The common height limit is 2.25 metres, rising with a higher water outlet.
3. Zone 2 is 0.6 m; outside the zones runs to 2.5 m (changed from 3 m under Amendment 2).
4. Zone 1 is measured from the outside edge of the bath.
5. A tool- or key-removable bath panel puts the space under the bath outside the zones.
6. IP ratings: IPX7 in Zone 0, IPX4 in Zones 1 and 2.
7. 30 mA RCD protection for all bathroom circuits (except SELV) and anything passing through Zone 1 or 2.

How Sparky Safety Can Help

Bathroom zones are exactly the kind of detail that separates a confident pass from a near miss. The Sparky Safety app is built to get you test-ready, with 300+ ECS HS&E practice questions across all 11 topic areas, plus realistic mock tests that mirror the real exam format.

For the technical side of the job, you also get 10 BS 7671 calculators, alongside reference guides and study guides that explain the regulations in plain English — including the kind of zone, IP rating and RCD detail covered here. Whether you are preparing for the ECS HS&E test, the AM2, or simply want to keep your knowledge current with Amendment 2, download the Sparky Safety app and give yourself the best chance of passing first time.