Why is my old cloth-covered electrical cable insulation becoming brittle and crumbly – Advice from Electriman, North London Electricians

If you have noticed that the fabric covering on your old electrical cables is crumbling away, or that the rubbery material underneath is cracking and falling apart when touched, this is a sign that your wiring has reached the end of its safe working life. This type of wiring is known as vulcanised rubber insulation, or VRI wiring, and it was standard in UK homes built or wired before roughly the 1960s.

Here is what is actually happening. The insulation on these cables is made from natural rubber, which was covered in a woven cotton or jute braid. Over decades of use, heat from the current flowing through the cable, exposure to oxygen in the air, and the natural ageing of the rubber cause it to harden, crack, and eventually turn to a fine black powder or crumble. Once this happens, the protective layer between the live copper conductors and everything around them is gone.

Why this matters to you as a homeowner:

1. Exposed or damaged insulation can allow the live copper wire to make contact with surrounding materials, including timber joists, plaster, or other cables, which can cause a fire inside your walls without any warning.

2. If the bare conductor is accessible, there is a direct risk of electric shock to anyone who touches it.

3. Most home insurance policies require your wiring to be maintained to a safe standard. Deteriorated VRI wiring could affect a claim.

What you should do right now:

1. Do not prod, pull, or dis

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Electriman covers Mill Hill, Barnet, Finchley, Edgware, Enfield, Watford and surrounding areas. All work is Part P certified and fully insured.