When is Rewiring Necessary?

If a property hasn’t already been rewired within the past 25-30 years, the chances are it will need upgrading at the very least in part in order to bring it up to current standards. If you’re planning major remodelling work that constitutes a material amendment as defined by the Building Regulations, it is likely that you’ll need to rewire part, if not all, of the property, including upgrading the consumer unit (fuse box). If you’re extending your home, or converting an attic or garage, this will constitute new work and therefore all of the new wiring must conform to Part P: Electrical Safety, and all existing wiring will need to be improved making sure that it is able to carry any additional loads safely, it is earthed to current requirements and that cross bonding is adequate. The rest of the existing wiring won’t have to be upgraded, except where upgrading is required by the energy-efficiency requirements of the Building Regulations, i.e. central heating controls.

You should be able to tell if a property has been rewired fairly recently by inspecting exposed parts of the wiring and by the electricity meter and fuse box (now referred to as a consumer unit). You can ask to do this when being shown around a house you’re contemplating 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 thoroughly rewiring.

With two or more sets of circuits, it might be challenging to know if all of them have been shut off when undertaking work and this is unsafe. Another tell-tale sign that a rewire could be necessary is a mix of different socket and switch styles. This could indicate that a partial rewire has taken place, specially when there is evidence of surface-mounted wiring running along skirting boards and up walls.

In some rare cases of properties that have not been re-designed in decades, you may still find example of old round pin sockets or original dolly switches, each of which are a sure sign that a rewire is needed.

Another clue is the colour and style of the cabling, which you should be able to see at light fittings, surrounding the fuse box. Modern C.A.B Electrical Services installations are wired in PVCu insulated cable coloured grey or white. Unless the wiring is the modern PVCu coated type, then a rewire may be required. 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 stop working, leading to short circuiting: a fire hazard and possible electrocution.

Even older PVCu cable may require replacing if it is not twin earthed cabling (with a second earth cable running from the outer sleeve), but this may only be apparent if you’re able to remove a switch or socket faceplate and look closely.

Checking for this conducting the viewing, and certainly isn’t advisable unless you are able to turn off the mains to begin with.

Should you be in any doubt, assume that a full rewire is necessary and budget accordingly. It might be that the system can be improved for less money by upgrading earthing and cross bonding.

If you proceed with the project, then before exchanging contracts you can arrange to get a certified electrician to do a survey and find out exactly what work is required. An electrician will generally charge ?100-150 for a survey with a verbal report. A full electrical survey with a written report will probably cost ?250-350.

Rewiring Work

A full rewire will cost approximately ?2-2,500 for a small property and considerably more for a larger property, excluding the expense of making good the decor. Fairly often, a full rewire can be averted, however; providing the existing cabling is sound and able to carry any extra loads, additionally, it could be possible to upgrade it by adding a modern consumer unit, proper earthing arrangements and cross bonding.

If rewiring work is required, it needs to be carried out at first fix stage (before plastering), concurrently as any central heating and plumbing work. New cabling can’t be surface mounted and so the installation consists of lifting the floor coverings and floorboards and maybe the skirting boards too, routing out channels in the walls and perhaps in some ceilings which are inaccessible from above. All of this work will cause serious disruption and so it is best not to try and live around the work whenever possible.

In addition to installing new cabling, first fix stage will involve installing 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 system controls, alarm systems, smoke detectors and doorbells, to add landscape lighting and sockets, and to rewire the telephones and tv aerial sockets. Additionally, it is worth improving the wiring plan for sockets and switches to make sure it meets your needs and those of modern-day housebuyers.

Think of specifying two-way or even three-way switching for halls and landings and other rooms exceeding one main access. For a high-value property, consider adding a separate 2amp circuit with separate switching for table and standard lamps in the primary living spaces and principal bedrooms. It can also be worth considering incorporating automated lighting, home network cablings, speaker cabling and other modern technology.

If the mains connection and meter demands moving, this will have to be carried out by the local electricity utility company. There will be a cost and several weeks notice is going to be needed.

Once the first fix stage has been carried out, the property can be re-plastered or the walls and ceilings filled and made good, and the floor covering replaced. The second fix work can then proceed fitting sockets and switch plates, light fittings, the consumer unit and wiring any electric fans, cookers, extractor hoods, electric showers and the immersion heater, if there’s a hot water storage cylinder.

For anyone who is working on a period building using vernacular materials, such as oak frame, cob or solid stonework, make sure your electrician is aware of this and has worked on such buildings.

(MORE: Electrical Sockets Explained)

Checking Earth Bonding

Earth bonding, often known as equipotential bonding and cross bonding, is vital for any electrical installation to be safe. Even if your remodelling project doesn’t require rewiring, make certain that the kitchen and bathrooms are earth bonded. Earth bonding will make sure that if a fault should occur causing the metal plumbing, bath, taps, radiators or boiler casing to become live, i.e. for current to flow through them, this will not trigger electrocution.

The reason the lack of earth bonding is often missed is because it doesn’t affect the functioning of the electrical circuits inside your home. To see if your project has been earth bonded, look under the sink or bath for metal clamps surrounding the copper pipes with green and yellow striped earth cable attached. All pipes in and out of the boiler and heating systems need earth bonding. If you’re building with plastic pipe as opposed to copper, you do not need to earth appliances but you have to earth the mains stopcock. If this is not the case, then arrange for the work to be done it is a crucial safety requirement.

Electrics in Wet Areas

There are special restrictions on electrical work in wet areas where there is the greatest danger of electrocution. No power sockets are permitted other than shaver sockets, which should be located away from the splash zone from showers. Switches in a bathroom should be pull-cord operation, or IR-type switches operated by battery or with just a really low voltage signal cable, such as Cat5e.

The I.E.E. Wiring regulations (BS 7671: 2001 Section 601) has mandatory conditions for areas containing a bath or shower. These safety standards are scored in zones, with the requirements for each zone being dependant upon the perceived amount of risk of electric shock. There are four zone categories: 0, 1, 2 and 3.

Zone 0: In the bath or shower. Any fittings used here have to be SELV (max 12V) and be rated IPX7 (protected against immersion in water).

Zone 1: Above the bath or shower to a height of 2.25m. A minimal rating of IPX4 becomes necessary.

Zone 2: The area stretching to 0.6m outside the bath or shower and above the bath or shower if over 2.25m. An IP rating with a minimum of IPX4 is needed.

Zone 3: Anywhere outside zones 0, 1 and 2. Where water jets aren’t to be used for cleaning purposes, the general rules of BS7671 apply. For detailed information, consult the I.E.E. Wiring regulations (BS 7671: 2001 Section 601).

For the latest I.E.E. regulations visit http://www.theiet.org

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