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Rubber-insulated (VIR), lead-sheathed and fabric-covered cables date from before the 1960s and degrade with age — the insulation becomes brittle and crumbles when disturbed, which is exactly what happens when someone changes a light fitting. Cable of this type is generally considered to be at the end of its serviceable life, and finding it is a strong indicator that rewiring should be assessed properly.
6 questions in this topic. General UK guidance, not advice about a specific property.
Rubber-insulated (VIR), lead-sheathed and fabric-covered cables date from before the 1960s and degrade with age — the insulation becomes brittle and crumbles when disturbed, which is exactly what happens when someone changes a light fitting.
Cable of this type is generally considered to be at the end of its serviceable life, and finding it is a strong indicator that rewiring should be assessed properly.
Before the harmonised colours came in (transition around 2004–2006), live was red and neutral black. Now live is brown and neutral blue; earth has remained green-and-yellow.
The overlap is dangerous: in an installation with both, a black conductor might be a neutral or might be a switched live or a phase. That is precisely why colour alone is never used to identify a conductor — it is proved dead by testing.
Lighting circuits installed before the mid-1960s frequently have no circuit protective conductor. That limits you to all-insulated fittings and switches — you cannot safely fit a metal switch plate or a metal light fitting to an unearthed point.
It is a very common driver for rewiring the lighting circuits, since people usually discover it when they want metal fittings or downlights.
Round-pin (BS 546) sockets in general use date the installation to before the widespread adoption of the 13A fused plug system, so typically pre-1960s. They usually come alongside rewireable fuses and no RCD.
Occasionally round-pin sockets are installed deliberately on a modern switched lighting circuit for table lamps — that is a different, intentional arrangement and is not a sign of age.
Asbestos flash guards were used behind some older fuse carriers and switchgear, and asbestos may be present in older meter boards or in the fabric around them. It is not disturbed by normal use, but it is relevant when equipment is being removed.
If asbestos is suspected, it should be assessed and handled by a licensed specialist. Mention it when you enquire so the work can be planned around it.
Listed building consent is often needed for work that affects the fabric, and chasing walls or lifting historic floors certainly can. Surface conduit, careful routing through existing voids, and sympathetic accessories are the usual approaches.
Involve the conservation officer early. Electrical work on these properties takes longer to plan and should not be booked as if it were a standard rewire.