Summary

Cable support sounds like the most boring part of a first fix, but two regulation changes in the past decade have made it the most legally fraught. Regulation 521.10.202 (introduced in the 18th Edition in 2018 and tightened in Amendment 2 in 2022) was a direct response to firefighter deaths at incidents where unsupported plastic clips melted in a fire, allowing cables to drape across escape routes. Any cable installed in a fire-escape route (corridor, stairwell, hallway through which occupants leave the building) must now have metal-fixed support throughout, not just at intervals.

The day-to-day quality issue, separately, is spacing. Cables sagging between clips are unsightly, get pulled out by other trades' work, and can compromise the mechanical protection assumed by the cable manufacturer's rating. The IET On-Site Guide (OSG) gives clear maximum spacings by cable type and orientation; most installers don't have the table memorised and instead clip "by eye," which is usually too generous.

The other widespread misconception is that SWA (steel wire armoured) cable can be clipped like T&E. It can't — SWA requires saddles or cleats sized for the cable diameter, with specific torque on the gland nut at termination. Using cable ties or oversized clips on SWA is a common defect picked up on EICR inspections.

Key Facts

Headline regulations

Maximum clip spacing (IET OSG Appendix E / common values)

Flat thermoplastic (T&E) cable, fixed to surface:

Circular thermoplastic / thermosetting cable, fixed to surface:

SWA cable (steel wire armoured), saddled or cleated:

Mineral-insulated cable (MICC / Pyro):

Values are approximate "typical maximum" figures used in the trade; always cross-check against the latest OSG table for the specific installation context.

Fire-rated cable for life safety circuits

Fire-rated cables MUST be installed with manufacturer-matched metal clips or cleats. Plastic clips, cable ties or trunking with plastic clips will fail before the cable does and breach the fire-survival rating.

Common fixing types

Conduit and trunking

Quick Reference Table

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Cable type Horizontal max spacing Vertical max spacing Fixing
Flat T&E 1.0–2.5 mm² 250 mm 400 mm Plastic clip + masonry nail (NOT in escape routes)
Flat T&E in escape route 250 mm 400 mm Metal clip or metal-supported tray
Round cable 9–15 mm dia 300 mm 400 mm P-clip
Round cable 15–20 mm dia 350 mm 450 mm P-clip
SWA 9–15 mm dia 350 mm 450 mm Saddle or cleat
SWA 16 mm² 4-core (approx 25 mm OD) 400 mm 550 mm Saddle or cleat
Fire-rated PH30 (BS 7846) Per manufacturer (typically 300 mm) Per manufacturer Metal clip or cleat, manufacturer-matched
Fire-rated PH120 Per manufacturer (typically 300 mm) Per manufacturer Metal cleat, BS EN 50368 rated
MICC 12 mm 900 mm 1,200 mm Copper or stainless P-clip
20 mm steel conduit 1,000 mm 1,500 mm Steel saddle

Detailed Guidance

Selecting clips for T&E

For 2.5 mm² T&E (the most common UK domestic cable), use a 6 mm flat clip with a 25 mm or 30 mm masonry nail into brick, block or plasterboard with timber behind. For chasing into walls before plastering, the cable can be fixed with cable clips at 250 mm spacing OR run in metal capping (steel oval conduit-style channel pressed into the chase) before plastering. Either is compliant; capping is now the preferred approach because it also satisfies regulation 522.6.204 (cables in walls less than 50 mm from the surface must have additional protection).

Where T&E runs through joist spaces in a floor void, regulation 522.8.5 means it must be supported by being clipped to the side of joists at not more than 1.5 m intervals OR drilled through joists (centre of joist depth, at least 50 mm from top and bottom edges). Loose cable resting on the ceiling below is non-compliant.

Regulation 521.10.202 in practice

If a cable run passes through any of the following, it is in an "escape route":

Cables in escape routes must be:

  1. Metal-clipped or metal-cleated to a non-combustible surface, OR
  2. Run inside metal conduit or metal trunking that is supported by metal fixings, OR
  3. Run on metal cable tray/basket supported by metal brackets — the tray must be supported such that it will not collapse in fire conditions.

Plastic clips, plastic cable ties on metal tray, plastic trunking, and stand-off plastic supports are all non-compliant in this context. Periodic clipping with metal at intervals is not enough — the rule is "throughout the length."

SWA cable installation

SWA (steel wire armoured) cable is the standard UK choice for sub-mains, garden runs, outbuildings, and any external below-ground route. Key installation points:

SWA installation checklist:
1. Use saddle clips or cleats sized to the cable OD — measure the cable
2. Clip spacing per OSG Table 4D (see Key Facts above)
3. At terminations: use the correct SWA gland (BW gland for indoor, CW for outdoor with shroud)
4. Earth the armouring at the gland via the gland plate / banjo washer
5. Pilot holes in masonry — never hammer directly through SWA
6. Minimum bending radius: 8 × cable diameter (smaller cables) or 6 × (larger)
7. Buried SWA: 600 mm minimum cover with marker tape; 750 mm under a road

Fixings into different substrates

Brick or block:

Plasterboard with timber behind:

Plasterboard cavity (no timber):

Concrete (precast, in-situ, screed):

Steelwork (purlins, rolled sections):

Drilling joists

When notching or drilling timber joists to run cables, BS 5268 (now BS EN 1995 / Eurocode 5) gives the limits:

Random cable runs across the top of joist ends are a structural defect and a fire hazard (cables crushed by floorboards).

Capping vs containment in walls

Where a cable is run in a wall chase, regulation 522.6.204 requires "earthed metallic covering" or other equivalent protection (e.g. 50 mm depth from surface, or an RCD on the circuit) where the cable is not run in a "permitted zone" (within 150 mm of corners/ceiling, or vertically above/below an outlet).

In practice:

Frequently Asked Questions

Do plastic cable clips on T&E breach Regulation 521.10.202 in a normal house?

Only if the cable is in an escape route. A normal house's hallway and stairs are escape routes for the occupants, so the strict reading is that any cable in a domestic hallway should be metal-supported throughout. In practice, building control and most inspectors apply the rule strictly only to common parts of flats, HMOs, and non-domestic premises — but the regulation does not formally exclude single dwellings. If in doubt, use metal clips or capping in hallways and stairwells.

Can I use cable ties on a metal cable tray?

Yes, where the tray itself is metal and the cable will not fall if the ties melt. The tray is the load-bearing element; ties are restraints. In an escape route, the tray's fixings to the building must be non-combustible (metal brackets, not plastic plugs into intumescent foam etc.). UV-rated ties are recommended for outdoor or exposed conditions.

How do I clip SWA cable to a timber post (e.g. for a garden shed feed)?

Use metal P-clips or saddle clips screwed into the post with stainless steel woodscrews, spaced per the SWA table (400–550 mm vertical for typical sizes). Pre-drill the post. Do not run SWA loose along the ground — bury it at 600 mm depth (per BS 7671 Table 522.8.10) with marker tape 150 mm above the cable.

What's the rule on cable clipped above suspended ceilings?

Cables above a suspended ceiling must be supported independently of the ceiling tiles. Loose cable resting on tiles is non-compliant (the tiles aren't a support). Use cable basket or tray fixed to the structural soffit, then clip cables to the basket. In escape routes (most suspended ceilings in commercial premises), the basket must be metal-supported per 521.10.202.

Are nail clips into mortar joints OK or do I need to plug-and-screw?

Masonry nails (40 mm, hardened) into a mortar joint are widely accepted and standard practice for T&E. They hold well in good mortar and don't damage face brick. Plug-and-screw is needed where the substrate is hard (engineering brick, high-strength block) or where vibration is expected. Don't nail into face brick if avoidable — it cracks the brick.

Regulations & Standards