BS 7671 (UK)

Updated 2 September 2026

BS 7671, the IET Wiring Regulations, is the UK’s authoritative electrical installation standard. The current version is BS 7671:2018+A4:2026, published by the IET and BSI on 15 April 2026. The previous version, BS 7671:2018+A2:2022+A3:2024, stays current alongside it until 15 October 2026, when it is withdrawn. WireSketch models a small set of 18th-edition baseline rules and does not encode any specific amendment. Here’s what that covers and what it doesn’t.

What BS 7671 is

BS 7671 is published jointly by the IET (Institution of Engineering and Technology) and BSI. It’s the standard cited by Part P of the Building Regulations for England and Wales, by the equivalent Scottish and Northern Irish technical standards, and by every UK electrical certification scheme (NICEIC, NAPIT, ELECSA, Stroma).

It’s a thick book. The parts most relevant to residential planning:

• Part 1, scope and definitions
• Chapter 41, protection against electric shock (RCD types, disconnection times)
• Chapter 43, overcurrent protection (RCBO, MCB ratings)
• Section 701, rooms containing a bath or shower (zones, IP ratings)
• Section 522, cable selection and erection (incl. the safe zones for buried cables)
• Appendix 15, ring + radial final circuit conventions (the UK’s distinctive ring main approach)

Which amendment is current

The 18th edition was published in 2018 and has been amended four times. Amendment 1 (2020) amended Section 722, EV charging installations. Amendment 2 (2022) tightened:

• AFDD (Arc Fault Detection Device) requirements for higher-risk locations (HMOs, care homes, student accommodation)
• Surge protection device requirements (Section 443)
• RCD type requirements where the load contains DC components (EV chargers, solar inverters, Type A no longer always sufficient, Type B may be needed)

Amendment 3 (BS 7671:2018+A3:2024) was issued on 31 July 2024, to be implemented immediately. It is a short amendment: two new definitions, bidirectional and unidirectional protective devices, and one new regulation, 530.3.201, on selecting the right kind where an installation has an additional source of supply such as solar PV or battery storage.

Amendment 4 (BS 7671:2018+A4:2026) was published on 15 April 2026 and can be applied immediately. Until 15 October 2026 both versions are current; on that date BS 7671:2018+A2:2022+A3:2024 is withdrawn and A4:2026 becomes the only current version. Its headline changes are a new chapter on stationary secondary batteries (electrical storage), new sections on functional earthing and bonding for ICT systems and on Power over Ethernet, and a major revision of Section 710 (medical locations). The AFDD requirement is reworded from “higher-risk” to “high rise residential buildings” (over 18 m or more than six storeys); the four building types where AFDDs are required on socket-outlet circuits up to 32 A, care homes, HMOs, purpose-built student accommodation and high-rise residential buildings, are unchanged.

WireSketch does not encode any of these amendments. Everything it models from BS 7671 predates Amendment 2; nothing introduced or tightened by Amendments 2, 3 or 4 is modelled.

Where it applies

• England + Wales, cited by Part P of the Building Regulations.
• Scotland, recognised via the Scottish Technical Handbook.
• Northern Ireland, recognised via local building control.
• Republic of Ireland, uses its own national rules (ET 101/I.S. 10101) that share IEC roots with BS 7671 but diverge in detail. WireSketch’s BS 7671 selector is a rough approximation for Ireland, not a substitute for the Irish standard.

Key requirements

• Cable, Twin & Earth (T&E) for fixed wiring in residential; SY/SWA for outdoor and buried.
• Ring main, 32 A ring final circuit serving up to 100 m² floor area, protected by 32 A MCB/RCBO.
• Radial circuits, lighting (6 A or 10 A B-curve), dedicated appliance loads (cooker, immersion, EV charger).
• RCD protection, 30 mA on all socket-outlet circuits up to 32 A (411.3.3), all lighting circuits in domestic premises (411.3.4, an 18th-edition requirement), all bathroom circuits, and buried cables less than 50 mm deep.
• Bathroom zones, IEC 60364-7-701 model: Zone 0 inside the bath, Zone 1 above, Zone 2 to the side. No 13 A sockets in Zones 1 or 2 (shaver supply only).
• Earthing, TT, TN-S, or TN-C-S system depending on supply; main equipotential bonding to incoming water/gas services.

What WireSketch models from BS 7671

• 150 mm horizontal and vertical cable safe zones per Section 522, drawn on the wall; cable runs are vertical or horizontal only, never diagonal.
• Default mounting heights of 45 cm for sockets and 120 cm for switches. These follow common UK accessibility practice, not a BS 7671 regulation.
• Bathroom zones in wet-room mode: Zone 0, Zone 1 and Zone 2 drawn around the water source up to 2.25 m above the floor, following the Section 701 / IEC 60364-7-701 zone model. Zone 0 blocks every fixture, Zone 1 allows fixed lights only, Zone 2 flags anything that is not splash-proof (IP44). Switches are expected outside the room.
• Twin & Earth cable with cross-section and current-rating suggestions; SWA where more than three cores are needed.
• A dual-RCD consumer-unit template: two 80 A, 30 mA Type A RCDs, 32 A Type B MCBs for ring final circuits, 6 A for lighting, and a 32 A cooker circuit. The template follows the conventional split-load layout (MCBs listed after each RCD), but the panel is a flat breaker list: the app does not model which circuits sit behind which RCD and never checks RCD coverage against 411.3.3 or 411.3.4.
• A 30 mA RCD line in the bill of materials for wet rooms.
• The Knowledge Base explains RCD types (AC, A, B and F) in general terms. The app’s templates and panel auto-fill always fit a Type A RCD; they never choose Type B for a circuit.

What WireSketch doesn’t model

• Anything amendment-specific: AFDDs (required since Amendment 2 in care homes, HMOs, purpose-built student accommodation and high-rise residential buildings), SPD selection (Section 443), RCD-type selection under 531.3.3, the bidirectional/unidirectional device rule of Amendment 3 (530.3.201), and the battery-storage and Power over Ethernet sections of Amendment 4.
• The minimum horizontal distance between a 13 A socket-outlet and Zone 1 in a bathroom; the app’s Zone 2 only asks for splash-proof equipment.
• Disconnection time calculations, required for Chapter 41 compliance, not modelled.
• Loop impedance and PSCC (prospective short-circuit current) values, site-measured during installation, not the planner’s scope.
• Ireland (ET 101 / I.S. 10101) deltas, the BS 7671 selector is an approximation; the Irish standard differs in detail.

Practical tip

For a UK homeowner planning a kitchen rewire: capture the layout in WireSketch, pick BS 7671 as the region, generate the Renovation Brief PDF, and hand it to a Part P-registered electrician. The electrician will translate your layout into a compliant design, perform the notifiable-work certification, and lodge the work with the relevant building control body. The brief saves them, and you, significant ambiguity in the quoting stage.