Signs You Need to Rewire

Old electrics are a hidden hazard in many London homes, and they often only get attention once something goes wrong. Here are the warning signs that your home needs rewiring, and what to do about them.

What are the warning signs?

Ten things, and the first two are worth more than the other eight put together.

1. Old rubber, fabric or lead-sheathed cable. Rubber insulation goes hard and cracks off the conductor, usually where the cable bends into a fitting. Once you can see bare copper at a light rose, the installation is finished.
2. An old fuse box with rewireable fuses, a wooden back or no RCD. A rewireable fuse offers no protection against an earth fault through a person.
3. Red and black cable cores. Harmonised brown and blue arrived in 2004, so red and black means the circuit is at least twenty years old, and black rubber means far older.
4. Frequent tripping or blown fuses, which usually means a real fault or moisture ingress rather than an over-sensitive device.
5. Flickering or dimming lights, often a loose connection at a junction or a failing neutral.
6. Scorch marks or brown discolouration around a socket or switch plate.
7. A burning smell from outlets or the consumer unit. Stop and call someone.
8. Buzzing accessories, or small shocks from switches and appliances.
9. No earth on the lighting circuit, common in pre-1966 houses, which rules out metal light fittings and switch plates.
10. Too few sockets, with extension leads permanently in use, or no rewiring in 30 years. Age alone is not a fault, but it is a reason to test.

What does an EICR actually tell you?

Whether the installation is safe to keep using, and exactly what has to be fixed. An Electrical Installation Condition Report is a physical inspection plus dead and live testing against BS 7671, the IET Wiring Regulations. Every defect is given a classification code, and the codes decide the outcome and your obligations.

An EICR costs £180 to £280 for a typical house, from around £150 for a one-bed flat to £375 for a five-bed. It is the cheapest useful thing you can do, and a page of C2s across every circuit is what turns a maybe into a rewire.

What is Part P notifiable work?

Electrical work in a home that has to be certified and notified to building control. Part P of the Building Regulations covers domestic electrical safety in England and Wales, and notifiable work includes a consumer unit replacement, any new circuit, and most work in bathrooms and shower rooms beyond a like-for-like accessory swap. A full rewire is notifiable in its entirety.

You have two routes. Either the work is done by an electrician registered with a competent person scheme such as NICEIC, NAPIT or ELECSA, who self-certifies and issues the building regulations compliance certificate, or you notify building control before work starts and pay them to inspect it. There is no third option, and the one that catches people out is finding at conveyancing that a kitchen or bathroom was rewired with no certificate. Retrospective sign-off is possible but slower and more expensive than doing it properly. See our guide to building regulations for how this fits with the rest of a project.

Consumer units and RCD protection

A modern consumer unit is a metal enclosure with residual current protection on the circuits that need it. Three requirements matter in practice. Domestic consumer units have needed a non-combustible enclosure since 2016, which is why plastic boards are being replaced. 30mA RCD protection is required for socket outlets rated up to 32A and for cables buried in walls at less than 50mm depth, which is nearly all of them. And surge protection is now expected in most dwellings unless a documented risk assessment says otherwise.

Individual RCBOs, one per circuit, are worth the extra over a split-load board with two shared RCDs. With a split-load board a fault on the fridge takes out every socket and half the lights. With RCBOs it takes out the fridge. A consumer unit change alone is £400 to £800, and it is notifiable work.

Why it matters

Degraded wiring is a genuine fire and electrocution risk, and the risk is highest where there is no RCD, because nothing then interrupts a fault current running to earth through a person. If you notice scorch marks, a burning smell or shocks, treat it as urgent and call a qualified electrician rather than waiting for the next stage of a project. Everything else on the list is a reason to book an EICR, not a reason to panic.

What does a rewire cost, and when should you do it?

A full rewire of a three-bed house costs £5,000 to £8,000 across the UK, with 20 to 30% added in London and the South East, which puts most London three-beds at roughly £6,000 to £10,000 including a new consumer unit, testing and Part P certification. A partial rewire of the circuits that failed an EICR is often the right answer instead. Expect five to ten days on site for a three-bed, longer if the house is occupied.

The best time is during a renovation, before plastering, when floors are up and walls are open. Run it after plastering and you pay for chasing, making good and redecoration on top of the wiring itself. Our order of works guide sets out where first fix sits in the programme, and the house rewire cost guide breaks the price down by property size. In period houses the routing matters as much as the price, which we cover in renovating a period property and renovating a Victorian terrace.

For an inspection and quote as part of a home renovation in London, contact us or call 07472 424 226.