Installation zones for concealed wiring (§522.6) — where a chased-in cable may run

The guide on proximity to non-electrical services (§528) covers the distance between an electrical conductor and a service of another discipline (water, gas). This article covers a different, often confused topic: where within a wall or partition a concealed electrical cable itself is allowed to run, to prevent someone later driving a nail or drilling a hole from hitting a live cable.

The problem: a chased-in cable is invisible

A cable that is routed in a chase in a wall or partition without its own mechanical protection (i.e. not in a metal or impact-resistant conduit) and then plastered or rendered over is completely invisible to a subsequent user of the space. Without additional rules, that person could drill through a live conductor without any warning while hanging a picture or a cabinet.

The installation zones

IEC 60364-5-52 §522.6 (mechanical protection of wiring) addresses this by only permitting a concealed cable without its own mechanical protection within fixed, predictable installation zones:

a horizontal and vertical strip running directly from a socket-outlet, switch or connection point to the cable (i.e. no diagonal or arbitrary routes);
a horizontal and vertical strip within 150 mm of a corner where two walls or partitions meet;
a horizontal strip within 150 mm of the ceiling or the top edge of the wall.

Outside these zones — for example a cable running diagonally across the middle of a wall to avoid an obstacle — a concealed cable without its own mechanical protection is not permitted.

What if the cable must run outside a zone, or sits shallow?

For a cable that lies outside the installation zones, or is embedded at less than 50 mm depth from the wall surface, additional protection is required. In practice this means one of the following measures:

Robust mechanical protection that prevents penetration by a nail or screw (for example an earthed metal conduit or sheath);
A residual current device (RCD) rated no higher than 30 mA on the relevant circuit, as additional protection against electric shock should the cable be struck anyway;
Wiring the circuit as SELV/PELV (see the guide on SELV/PELV/FELV), where the low voltage removes the shock risk from penetration.

Note: this article covers the underlying principle from IEC 60364-5-52 §522.6 based on independently verified sources. The precise numbered sub-clauses may differ in detail between the international base text and the Dutch NEN 1010 implementation — always consult the full NEN 1010 text itself for the exact clause numbers and any national deviations for a specific design (for example for walls with a metal internal frame, which typically face stricter requirements regardless of cover depth).

Practical relevance

During a renovation adding a new socket-outlet or switch, the new cable must either run directly (horizontally or vertically, no diagonals) to the nearest connection point or a corner/ceiling zone, or — if that is not feasible given the layout of the space — be fitted with one of the additional protection measures listed above. This is particularly relevant in older renovations where cables sometimes run haphazardly through a wall because the installer was unaware of the zone requirement.

Common mistakes

Routing a cable diagonally through a wall to take a shortcut, without keeping the cable within an installation zone or applying additional protection.
Assuming a sufficiently deep chase (for example >50 mm) alone already satisfies all requirements — the zone requirement and the cover-depth requirement are two separate criteria that apply alongside each other, not as substitutes.
Ignoring a metal internal frame in a partition (for example a metal-stud wall) — such partitions often face stricter requirements regardless of cable cover depth.
Confusing the installation-zone requirement with the distance requirement to non-electrical services (§528) — these are two different rules with a different purpose: one protects against penetration from within a wall, the other against mutual interference between different disciplines.