"The flat is old, so it probably needs a rewire." That sentence gets said a lot in Central London, and it is wrong roughly as often as it is right. Age is not a condition. A carefully installed circuit from the 1970s that has been left alone can test perfectly well; a circuit installed in 2005 by someone in a hurry, then hacked about by three subsequent kitchen fitters, can be a genuine hazard. What decides a rewire is what the testing says and what the building will let you do — not the date on the deeds.
This guide is about rewiring in period property specifically: Georgian and Victorian terraces, Edwardian mansion blocks, and the conversions carved out of both. The electrical content of a rewire is standard. The hard part, in a listed or protected building with no loft and no underfloor access, is getting the cable from A to B without destroying something that cannot be replaced.
Deciding whether you need one at all
A rewire is a big, disruptive, expensive intervention, and it should be justified by evidence. The evidence normally comes from testing — an inspection of the installation that measures the condition of the cable and the integrity of the earthing, rather than an opinion formed by looking at the sockets. Our guide to EICR costs covers what that inspection involves and what its coded observations mean.
The findings that genuinely point towards a rewire tend to be these. Insulation resistance readings that are poor across multiple circuits, which usually means the cable itself is degrading rather than one bad connection. Rubber-insulated or lead-sheathed cable still in service — it perishes with age and heat, and once it starts, it starts everywhere at once. Lighting circuits with no circuit protective conductor, so nothing can be earthed. Fabric-covered flex feeding fittings. Cable that crumbles when it is flexed at a terminal. An installation so extended and re-extended that no one can say what feeds what.
By contrast, none of these are, on their own, a reason to rewire: an old-looking board (that is a board replacement question), too few sockets, a single dead circuit, or a nuisance trip. Those are smaller jobs, and it is worth insisting on that distinction, because "rewire" is sometimes reached for when "diagnose properly" would have done. If a fault is what is driving you, start with proper fault finding.
Full or partial
Partial rewires get a bad name they do not always deserve. If the ring circuits are sound and the lighting is the problem, replacing the lighting and leaving good cable in place is a reasonable engineering decision, not a compromise. What makes a partial rewire go wrong is doing it without testing the part you are keeping, so you end up with a beautiful new installation joined to a bad old one at a junction nobody can find later.
The honest test is: can the retained circuits be tested, proven, and documented? If yes, a partial is legitimate. If nobody can even establish where the retained circuits go, you are not saving money, you are deferring it.
The real problem: routes through historic fabric
In a modern house, a rewire means dropping cable from the loft and pulling it under the floor. Neither of those exists in most Central London flats. There is no loft, because there is a neighbour above. There is often no accessible underfloor void, because the floor is a structural deck shared with the flat below, and lifting it is both a construction question and a lease question. So cable routes have to be found in the fabric itself, and the fabric is frequently protected.
The specific difficulties, in the order they usually bite:
- Lime plaster on lath. Chasing into it is not like chasing into modern render. It cracks well beyond the cut, the laths behind it are structural to the plaster, and repair is a specialist plastering job rather than a bag of filler.
- Cornices, dado rails, architraves and panelling. These are exactly where a cable would naturally want to run, and exactly what a listed building's significance often rests on.
- Original floorboards. Wide pine boards can be lifted, but they need lifting properly — cutting them for convenience is a permanent loss, and a good electrician will lift and refix rather than cut through.
- Party walls. Chasing deeply into a wall shared with the neighbouring property can bring the Party Wall etc. Act 1996 into play for notifiable works. Whether it does depends on what is being cut and how deep; take advice rather than assume it does not apply.
- Solid walls with nowhere to hide. Sometimes the only compliant answer is surface containment, or a route through a later-added partition, or accepting a socket where the building allows one rather than where the furniture wants one.
The craft here is finding the reversible route. Period buildings in W1 and W2 have usually been serviced three or four times over, and each generation left voids, redundant chases, boxed corners, later stud walls and dead service runs. Those are gold. A rewire designed around what previous generations already disturbed does a fraction of the damage of one designed on a drawing. This is the single biggest difference between an electrician who works in this stock and one who does not.
Consents: check before you cut, not after
Electrical work in dwellings falls under Building Regulations Part P, and the installation must be designed and tested to BS 7671. A rewire is notifiable work and must be certified. That much is straightforward.
The rest depends on your building. If it is listed, works affecting its special character typically require listed building consent, and that duty applies inside as well as out — chasing walls, lifting original floors and cutting into panelling or ceilings are all capable of engaging it. Do not rely on the fact that the work will be hidden when it is finished; the test concerns the fabric affected, not the final appearance. Confirm the position with the council's conservation team before work is designed. In a conservation area, additional planning controls may apply to anything external. Our guide to downlights in a listed building goes into the practical side of that.
If you are a leaseholder, most leases require the freeholder's or managing agent's consent for alterations, usually through a licence to alter, and a rewire will normally qualify. Many freeholds in Mayfair, Marylebone and the surrounding areas sit with large estates, and their requirements vary — read your lease and ask, rather than assuming your neighbour's experience applies to you. Our guide to a licence to alter in a mansion block sets out how that usually runs. Where a whole building is being rewired at the freeholder's instigation, Section 20 consultation under the Landlord and Tenant Act 1985 applies to works over £250 per leaseholder.
Sequencing: a rewire is a building job wearing an electrician's coat
Clients are frequently surprised that the electrical work is the short part. A rewire runs in two passes. First fix puts the cable in — chasing, lifting floors, running everything back to the board, fitting back boxes — and leaves the property looking considerably worse than when it started. Then plastering and making good. Then second fix: the accessories, the fittings, the board, and testing. Then decoration.
That order has consequences worth understanding before you commit. Almost every wall the cable touches will need making good and redecorating, which means a rewire effectively drags a decoration project behind it. It is why rewires are usually done as part of a wider refurbishment rather than on their own — if the walls are coming back anyway, that is the moment to do it. It is also why doing a rewire and then a kitchen the following year is a poor plan, and doing them together is a good one.
Living in it, or not
An empty flat can be rewired in one continuous run: everything off, everything open, everything done. An occupied one has to be staged room by room, with power maintained somewhere, dust screens up, and floors reinstated at the end of each day. That is slower and it costs more, and it is often still the right answer for someone who cannot move out. The point is to decide deliberately rather than discover it halfway through.
Central London adds its own layer. Many blocks restrict working hours and require works to be booked with the managing agent. Lifts need protecting and often booking. Waste from a rewire — plaster, old cable, old accessories — has to come out through a communal entrance and be removed by vehicle from a street with no loading. None of it is unusual. All of it is time that belongs in the programme rather than in a surprise.
What drives the cost
We do not publish a rewire figure, because a rewire priced without seeing the building is fiction. What moves it: the number of circuits and accessories; whether routes exist or have to be created; the amount of making good; whether floors can be lifted and refixed or must be worked around; whether the fabric is protected and the design has to bend to it; whether the property is occupied; whether the board and supply arrangements need work too; and how much of the existing installation can be tested and honestly retained. Our electrical work starts from £80 and set prices are on the electrical page; for a rewire, we survey, test, and give you a fixed price against a written scope before anything is cut.
How we handle it
We test before we recommend. If the testing does not support a rewire, we will tell you that, even though a rewire is the bigger job. If it does, we design the routes around what the building will tolerate, agree the making-good scope in advance so it is not a fight later, and give you one point of contact for the electrical, plastering and decoration sequence rather than three trades blaming each other. Work in W1's listed stock is handled by the same team behind our Mayfair electrician page.
If you want a straight answer on whether your property needs rewiring, get in touch and we will start with the test results rather than the sales pitch.