Reference
Identify old UK house wiring
The insulation on a cable is a fair-enough clue to the era it was installed. Anything rubber-insulated is life-expired; anything with a green-only earth predates 1977; anything with red/black cores predates the 2004 harmonisation. Here's what to look for in a typical UK property, and what each era tends to mean for safety.
Pre-1955 · Rubber (VIR) & lead-sheathed
What it looks like
Black rubber insulation over copper, often inside a lead outer sheath. Round tinned-copper conductors. Cloth or fabric wrapping under the rubber.
Why it matters
Rubber perishes with age — insulation cracks and falls off, especially where it enters ceiling roses and switches. Considered life-expired. Lead sheath is not itself dangerous but the internal insulation almost certainly is.
Typical verdict
Full rewire required.
1955–1965 · Early PVC, imperial sizes
What it looks like
Red (line), black (neutral), green (earth). Twin-and-earth style but cable sizes marked in imperial: 3/.029, 7/.029, 7/.036 etc.
Why it matters
Early PVC can go brittle; single-colour green earth (not green/yellow) dates it. Often lacks a CPC (bare earth) in lighting circuits.
Typical verdict
Test-and-inspect; usually replace on next major works.
1966–1970 · PVC transition
What it looks like
Red / black / green earth still, but metric cable sizes appear (1.0, 1.5, 2.5 mm²).
Why it matters
Green-only earth remains. May not have a CPC in every lighting circuit.
Typical verdict
EICR to assess condition; often serviceable if undisturbed.
1970–2004 · Modern PVC, old colours
What it looks like
Red (line), black (neutral), green/yellow (earth) fixed wiring. Brown/blue/green-yellow flex from 1970 onward.
Why it matters
Cable itself is usually fine. Risk lies elsewhere: no RCD protection, wooden-back consumer units, lack of main bonding, borrowed neutrals from lighting alterations.
Typical verdict
EICR + likely consumer unit upgrade rather than rewire.
31 March 2004 onward · Harmonised colours
What it looks like
Brown (line), blue (neutral), green/yellow (earth) fixed wiring — matching flex colours.
Why it matters
Modern cable. Where old and new colours coexist in a board, a warning label to Reg 514.14 is required.
Typical verdict
Current standard.
Other tell-tale signs of an older installation
- Round pin sockets (2 A / 5 A / 15 A) — pre-BS 1363, most from before 1947.
- Wooden-back or cast-iron fuse boxes, rewireable fuses instead of MCBs — usually pre-1980.
- Cloth-covered flex on pendant lights — indicates lighting hasn't been touched in decades.
- No main bonding on incoming gas and water pipes — a common finding on pre-1980 installations.
- No RCD on any circuit — a legitimate EICR failure item on any modern report.