Rewiring is expensive and disruptive, so the question of whether you can do half of it is entirely reasonable. The honest answer depends on what condition the remaining wiring is in, whether the two halves can be safely joined, and whether the money saved now will simply be spent again in three years. This guide sets out how to make that judgement with evidence rather than optimism.
What each option means
A full rewire replaces all circuit wiring, accessories and usually the consumer unit throughout the property. A partial rewire replaces defined sections: perhaps all the socket circuits but not the lighting, or the ground floor but not the first, or the kitchen and bathroom only.
Both should end with a proper certificate. In a partial rewire, the certificate covers the new work and the existing installation is reported on separately, including any limitations.
When a partial rewire genuinely works
Partial rewiring makes sense when the remaining wiring is demonstrably sound: modern cable in good condition, satisfactory insulation resistance readings, no deterioration and no unsafe alterations. It also makes sense when a specific area is being renovated and the rest of the house was rewired relatively recently.
- Kitchen or bathroom refit where the rest of the house tests well
- Extension circuits added to a sound existing installation
- One floor rewired during a loft conversion or renovation
- Replacing a single deteriorated circuit identified by testing
When it becomes false economy
If the untouched wiring is rubber or fabric insulated, if insulation resistance is marginal across several circuits, or if the installation has a long history of ad hoc alterations, a partial rewire leaves you with a house that will need the same disruption again shortly. Doing half the job twice costs more than doing all of it once, because the setup, lifting, chasing and making good are repeated.
There is also a practical point about decoration. Rewiring makes mess. Doing it in two phases means redecorating twice.
How testing informs the decision
This decision should be made on test results, not on guesswork. An inspection with insulation resistance testing on each circuit tells you which circuits are sound and which are deteriorating. That converts an opinion into a list.
Ask for the results, not just the conclusion. Circuit by circuit readings let you see whether the case for a full rewire is based on evidence.
Cost and disruption compared
A full rewire costs more in absolute terms but less per circuit, because access, setup and making good are done once. A partial rewire has a lower headline figure and much less disruption to the areas not being touched, which matters greatly if you are living in the property.
Where budget is the constraint but the whole installation needs work, a phased full rewire with a defined plan is usually better than an open ended partial. Agree the phases and the order in advance.
Joining old and new safely
Where new wiring meets existing wiring, joints must be accessible or made in maintenance free enclosures, and the earthing arrangement must be consistent across the whole installation. Older installations sometimes have undersized or missing circuit protective conductors, particularly on lighting, which limits what can be safely connected.
If lighting circuits have no earth, adding new metal fittings to them is not appropriate, and that alone often decides the scope of a partial rewire.
Getting a comparable quote
Ask for both options priced against the same test results: full rewire, and partial with the scope written out circuit by circuit. Ask what the electrician would do in their own house. A clear answer with reasons is a good sign; a reluctance to price the smaller option is not.
Documenting the scope
Whichever route you take, get the scope written down circuit by circuit before work starts, along with what happens to the circuits that are not being replaced. Those remaining circuits should be tested and reported on, so that you know their condition rather than assuming it. That document becomes useful evidence at sale, and it tells any future electrician exactly which parts of the installation are new and which are original.
Common questions
- Can I rewire one floor at a time?
- Yes, provided the joining arrangements and earthing are sound and the scope is clearly documented.
- Will a partial rewire pass an inspection?
- The new work is certified; the remaining installation is reported on with any observations noted.
- Is partial rewiring cheaper overall?
- Cheaper now, but more expensive if the rest of the wiring needs doing within a few years.
- How do I know which circuits are bad?
- Insulation resistance testing circuit by circuit. Ask for the numbers, not just a verdict.
- Do I need to move out?
- Rarely for a partial rewire. A full rewire in an occupied house is possible but disruptive.
We test circuit by circuit and price both options honestly, so you can see the evidence behind the recommendation.
Related guides
- What Drives the Cost of a House RewireA rewire is priced on access and disruption far more than on cable.
- When Does a House Need RewiringAge is a clue. Condition and test results are the evidence.
- Rewiring a House You Are Still Living InIt is entirely possible to live through a rewire. It is much easier if the phasing is agreed before anyone lifts a floorboard.