Purpose

Route concealed cables in walls while coordinating prescribed zones, additional protection, penetration depth, structure, fire, and future fixings.

Learning objectives

• Explain prescribed wall zones
• Assess depth and additional protection
• Protect structure
• Document concealed routes

Concealed cable safety combines electrical rules with how occupants later drill, nail, alter, or repair the building. A straight-looking route is not automatically a recognised zone.

Core theory

Current BS 7671 defines permitted zones relative to visible accessories and wall edges/ceilings, with separate solutions for sufficient depth or suitable mechanical protection/earthed containment.

RCD additional protection may be required for concealed cables even when routed in prescribed zones; it does not remove route, enclosure, or mechanical requirements.

Chases and notches must comply with structural guidance and avoid weakening joists, lintels, fire barriers, acoustic layers, damp control, and other services.

Assumptions: No earthed protection or sufficient depth shown.

1. Zone: A diagonal between accessories is not established as a prescribed route.
2. RCD: Additional protection does not make an unrecognisable route acceptable by itself.
3. Redesign: Use a compliant zone or another current permitted protective method, then verify structure and circuit.

No; reroute or provide a fully compliant alternative protective arrangement.

Reasonableness check: Future drilling risk remains even though an RCD may reduce some consequences.

Knowledge check

Answer: No. Route and mechanical/depth requirements remain.

Practical exercise

Draw allowed conceptual zones around accessories on a sample wall, then flag routes needing exact current-standard dimensions.

Summary

• Concealed routes must be predictable
• RCD is additional protection
• Structural rules also govern chases