It depends on what the existing wiring is and how it tests, not on the age of the house. If an EICR shows most circuits are sound PVC cable, a partial rewire of the problem areas, an extension or a new kitchen is often enough. If the house still has rubber or lead cable, lighting circuits with no earth, or C2 faults spread across many circuits, a full rewire is usually better value and safer in the long run.
What is the difference between a partial and a full rewire?
A full rewire replaces every circuit in the property. A partial rewire replaces some circuits and keeps the rest, because they have been tested and found fit to stay.
- Full rewire
- All cables, sockets, switches and light points replaced, usually with a new consumer unit.
- Partial rewire
- Selected circuits, a floor, a room or an extension rewired. The rest kept.
- Not a rewire
- Repairing a few faults, adding sockets or replacing the consumer unit alone.
How do I find out which one I need?
Get an Electrical Installation Condition Report (EICR) first. It is the evidence that should drive the decision, not a guess from the age of the house or the colour of the wires.
An EICR tests each circuit, including insulation resistance, earth continuity and how quickly protective devices disconnect a fault. It records what type of cable is installed and codes any defects as C1, C2, C3 or FI.
Read it circuit by circuit. If one or two circuits fail and the rest test well, that points towards a partial rewire or targeted repairs. If poor results run through most circuits, a full rewire is usually the honest answer. Ask the electrician to show you the results that support their recommendation. A good one will happily explain them.
When does a partial rewire make sense?
When most of the wiring is sound and the work is focused on one area or one change in how you use the house. These are the common cases:
- A new extension
- New circuits for the extension, with the existing house tested and kept.
- A kitchen refit
- New circuits for the cooker, sockets and appliances while the walls are open.
- A loft conversion
- New lighting and sockets for the new rooms.
- One floor that tests badly
- Often the upstairs lighting, or a floor that was never updated.
- Damaged circuits
- Cable damaged by building work, water or rodents in one area.
- Sound wiring elsewhere
- PVC cable that tests well and has earths throughout.
When is a full rewire the better choice?
When the problem is the installation as a whole, not one part of it. Patching wiring that is failing everywhere tends to cost more over time and still leaves risk behind.
- Rubber or fabric-insulated cable
- The insulation goes brittle and crumbles. It can't be repaired.
- Lead-sheathed cable
- Very old and well past its expected life.
- No earth on lighting circuits
- Common in older houses and a problem with metal fittings.
- Several C2 codes across circuits
- Faults spread through the house, not in one place.
- Poor insulation readings throughout
- A sign the cable itself is deteriorating.
- A major renovation
- Floors up and walls being replastered anyway.
Can old and new wiring be mixed?
Yes, as long as the old wiring is safe and in good condition. A partial rewire is exactly that. But the new work must meet the current Wiring Regulations (BS 7671), and the electrician must check that the existing installation can safely support it.
That check covers things like the earthing arrangement, main protective bonding to water and gas pipes, and whether the existing circuits will work with modern protection. If the earthing or bonding falls short, it has to be put right before the new work can be signed off, even if you only asked for one new circuit.
The new circuits are recorded on an Electrical Installation Certificate (EIC). The old parts aren't certified by it, so it's sensible to keep a recent EICR alongside it.
Why is the consumer unit often replaced too?
Because new circuits need modern protection, and an old fuse box or early consumer unit often can't give it. Most new circuits need RCD protection, and an old board may have no spare ways or no RCDs at all.
Current rules for domestic consumer units also call for an enclosure made of non-combustible material, usually metal. Many older plastic boards don't meet that.
There is one catch with a partial rewire. When older circuits are moved onto a new board with RCD protection, small leaks to earth that were hidden before can start causing trips. That's usually a sign that the old circuits need attention, and it's better to find out at the survey than after the work. A good electrician tests the circuits being kept before agreeing what goes on the new board.
How disruptive is each option, and can it be done in stages?
A partial rewire is less disruptive because only part of the house is affected. A full rewire can still be staged so you can live in the house, but expect dust, noise and some days with limited power.
Staging often works floor by floor or circuit by circuit, with power restored to finished areas at the end of each day. Clearing rooms, or moving furniture to the middle and covering it, speeds things up. Kitchens and bathrooms are easiest done when they're out of use anyway.
If you plan to do a full rewire over time, get the whole job designed at the start. That way each stage fits the final layout and you don't pay to redo work later. Be aware that the house may stay partly on old wiring between stages, so the remaining circuits should be safe in the meantime.
Should I rewire before or during a renovation?
Before the plastering and decorating, always. Rewiring means cutting chases in walls and lifting floorboards, so doing it while the house is already disrupted saves doing the mess twice.
It's also the cheapest time to add what you'll want later: extra sockets, USB points, outdoor sockets, a circuit for an EV charger, data cabling or better lighting. Plan the electrics with your builder's schedule so first fix happens before plaster and second fix after decorating. If the renovation covers most of the house, a full rewire often costs little more than a large partial one, and leaves no old wiring behind.
Does it matter if I'm selling or buying?
It can. A buyer's surveyor will often flag old wiring and recommend an EICR, and an unsatisfactory report can lead to a price renegotiation. Sellers who have a recent EICR, and certificates for any rewiring, give buyers clearer answers.
If you're buying, an EICR before you complete tells you whether you're facing a partial or full rewire, which helps you budget or negotiate. Conveyancers often ask for the Building Regulations compliance certificate and EIC for notifiable electrical work, so keep them safe.
If you're selling, a full rewire just before selling isn't always worth it. A partial rewire of clear problems, plus a satisfactory EICR, may be enough. When you're ready, we survey the property and give you one fixed price for whichever option the evidence supports.
Questions
Is a partial rewire always cheaper?
Usually, because there is less cable, fewer points and less making good. But if most circuits need replacing anyway, several partial jobs over the years can end up costing more than one planned full rewire.
Can a full rewire be done without a new consumer unit?
Rarely. A full rewire is normally designed around a new board with RCD protection for the new circuits. If you already have a modern consumer unit in good condition, the electrician may be able to keep it.
Will the new wiring be certified if the rest of the house isn't?
Yes. The new circuits get an Electrical Installation Certificate and are notified to building control. The certificate covers the new work only, so a recent EICR is the record for the rest.
Does a partial rewire mean less redecorating?
Yes, only the affected rooms need making good and redecorating. Some routes can use existing voids, loft spaces and floor voids, which reduces chasing. Ask at the survey which walls and floors will be opened.
Can a landlord do a partial rewire to pass an EICR?
Yes, if the unsatisfactory items are confined to certain circuits. Landlords in England must fix C1, C2 and FI items within 28 days or sooner if the report says, and then get written confirmation the work is done.
My electrician says full rewire but the EICR shows few faults. What should I do?
Ask them to explain which results support it. If you're not convinced, a second opinion from another registered electrician is reasonable. A rewire is a big job, and the evidence should be clear.