Updated: Dec 27, 2020
Find out when rewiring is necessary and the building regulations related to wiring work and electrics.
At worst, faulty electrics can be a serious fire hazard and can lead to injury or electrocution. This is why electrics were brought in to the building regulations under Part P. Existing wiring installations are not covered, but if you make significant alterations or new additions to the wiring in your home, the regulations come into force.
If you are thinking of buying a property more than 25 years old, it is important to check that the wiring is up to date before you buy. Ideally, you will get an idea of what work is required and an estimate of the likely cost so that you can take this into account when assessing the feasibility of the project and how much to offer.
Even if you already own the property you are renovating, it is important to know early on if any rewiring work will be necessary, as it can be very disruptive to the fabric and decor of the building, and so is best completed early on, before any re-plastering or redecorating work takes place.
When is Rewiring Necessary?
If a property has not already been rewired within the last 25-30 years, the chances are it will need upgrading at least in part in order to bring it up to current standards. The wiring may be potentially dangerous and may not be able to cope with the demands of modern living.If you plan major remodeling work that constitutes a material alteration as defined by the Building Regulations, it is likely that you will need to rewire part, if not all, of the property, including upgrading the consumer unit (fuse box).If you are extending your home, or converting an attic or garage, this will constitute new work and therefore all of the new wiring will have to conform to Part P: Electrical Safety, and all existing wiring will have to be improved to ensure that it is able to carry the additional loads safely, it is earthed to current requirements and that cross bonding is satisfactory.Where you are extending or remodeling, the rest of the existing wiring does not have to be upgraded, except where upgrading is required by the energy efficiency requirements of the Building Regulations, i.e. central heating controls.
How to Tell if Your Property has Been Rewired
You should be able to tell if a house has been rewired recently by inspecting exposed parts of the wiring and by the electricity meter and fuse box (now known as the consumer unit). You can ask to do this when being shown around a property you are thinking of buying, or by inspecting your home. If there is an old-fashioned-style fuse box, with big white ceramic-style fuses, then the chances are that the property needs completely rewiring.
With two or more sets of circuits, it can be very difficult to know if all of them have been disconnected when undertaking work and this is unsafe. Another tell-tale sign that a rewire may be necessary is a mix of different socket and switch styles. This could indicate that a partial rewire has taken place, especially if there is evidence of surface-mounted wiring running along skirting boards and up walls.
In some rare cases of properties that have not been renovated in decades, you may still find example of old round pin sockets or original dolly switches, both of which are a sure sign that a rewire is necessary.
Another clue is the colour and style of the cabling, which you should be able to see at light fittings, around the fuse box. Modern electrical installations are wired in PVCu insulated cable coloured grey or white, and a modern consumer unit will have circuit breakers and residual circuit devices (RCDs).
What if it has not Been Rewired?
Unless the wiring is the modern PVCu coated type, then a rewire is likely to be necessary. If you see any old rubber insulated cabling, fabric insulated cabling (used until the 1960s), or lead insulated cabling (used until 1955) then it needs replacing as the insulation can rot and/or break down, leading to short circuiting: a fire hazard and potential electrocution.
Even older PVCu cable may need replacing if it is not twin earthed cabling (with a second earth cable running within the outer sleeve), but this may only be evident if you are able to remove a switch or socket faceplate and look closely.
Checking for this conducting the viewing, and certainly is not advisable unless you are able to turn off the mains first.
If you are in any doubt, assume that a total rewire is required and budget accordingly. It may be that the system can be improved for less money by upgrading earthing and cross bonding.
How Much Does an Electrician’s Survey Cost?
If you proceed with the project, then before exchanging contracts you can arrange to get a qualified electrician to do a survey and find out exactly what work is required.
An electrician will typically charge £100-150 for a survey with a verbal report.A full electrical survey with a written report is likely to cost £250-350.
Before Your Rewiring Work Starts
Rewiring a property is messy, disruptive work. It happens in two stages: first fix, when cables and wiring are installed, and second fix when everything is joined up or made ‘live’, when the front faces of sockets, switches and lights are fitted. Those runs of wires go everywhere: under floors, through walls and across ceilings, so first fix is best done without carpets or furniture, so floorboards can be lifted and ceilings cut into. To position new sockets and switches at legally correct heights, plaster generally needs to be chased into, too.
This is why it’s important to plan what’s going where in each room before starting the first fix stage, so you know where you need lights, plug points and any other electrically driven items. Additions mid-way through are costly and time consuming.
One way to prepare is by drawing a plan of your home with each room on graph paper and marking up the position of beds, sofas, kitchen units and so on. You can then consider the lighting and switches required. Little things like under-cabinet and bedside lighting are easy to do when planned from the start, but costly to undertake later. As well as thinking about task, mood and feature lighting, remember smoke and heat alarms, garden RCD safety sockets and external security lights.
Think about future proofing
Today we are a super-consuming society hooked on ‘tech’. In terms of electrics, this means mood lighting, surround sound, high-speed Wi-Fi, kitchen gadgets and TVs in the bathroom. Electrical circuits must be up to the job — and you need to plan ahead. Do you want Ethernet cable to every room to ensure uninterrupted Wi-Fi (or perhaps just living spaces and bedrooms)? Will you want speakers in each room or a security system?
Move out if possible
Full rewires usually happen when homes are empty, but for hardened homeowners it is possible to live in one room while having works happen around you. If you can’t move out, then dust-cover furniture and expensive items, preferably moving electrical equipment into a separate room, as this is not your electrician’s responsibility. Get your electrician to install the new consumer unit and prep your habitable room with a temporary supply of sockets.
How Much Will Rewiring Cost?
The cost of rewiring, including first and second fix with standard sockets and switches and excluding light fittings, should be around £1,000-£1,500 for a kitchen extension. The UK average cost for rewiring a three-bed semi is £3,500; the price will vary depending on where you live. Other variables include the size of the house, how accessible/empty the property is and the complexity and standard of the finish.
Very often, a full rewire can be avoided, however; providing the existing cabling is sound and able to carry any additional loads, it also may be possible to upgrade it by adding a modern consumer unit, proper earthing arrangements and cross bonding.
How Long Will the Rewiring Take?
A kitchen rewire may take two days, a three-bed semi probably two days to first fix, then the same again to second fix. A larger property will take much longer.
What is Involved When Rewiring?
If rewiring work is required, it should be undertaken at first fix stage (before plastering), at the same time as any central heating and plumbing work. New cabling cannot be surface mounted and so the installation will involve lifting the floor coverings and floorboards and possibly the skirting boards too, routing out channels in the walls and possibly in some ceilings that are inaccessible from above. All of this work will cause major disruption and so it is best not to try and live around the work if possible.
As well as installing new cabling, first fix stage will involve fitting new back boxes for all sockets and switches. In addition to rewiring for all power and lighting circuits, it is a good opportunity to rewire for modern central heating controls, alarms, smoke detectors and doorbells, to add outdoor lighting and sockets, and to rewire the telephones and television aerial sockets. It is also worth redesigning the wiring plan for sockets and switches to make sure it meets your needs and those of modern house buyers.