Electrical alterations

All new electrical work must comply with Part P of the Building Regulations which restricts DIY electrical work on grounds of safety. However, you are still allowed to carry out some work yourself without notifying Building Control. Minor repairs and maintenance are permitted, as well as ‘like for like’ replacements, such as changing existing sockets, switches and ceiling pendants or even replacing damaged cables. As long as the job isn’t within a ‘special location’ such as a bathroom or outdoors, you’re also allowed to install additional new light fittings, switches, sockets and even add a single fused spur to an existing circuit (a ‘spur’ is a new cable and socket run as a branch from an existing socket on the ring main).

Everything else, such as installing complete new circuits or changing a fuse board for a consumer unit, is classed as ‘notifiable work’. This requires a Building Regulations application to be made in advance so the work can be inspected and checked. However, in most cases the electrician can self-certify their work as they’re normally registered with a body that gives them the necessary ‘registered installer’ status (also known as ‘competent persons’) such as the ECA (Electrical Contractors Association) or NICEIC (National Inspection Council for Electrical Installation Contracting).

A ‘non-qualified’ person can still carry out notifiable electrical work as long as Building Control are informed – but if you fail to do this and the work is found to be unsafe, it can lead to a hefty fine. Upon completion of the job, it is a legal requirement for the electrician to test the new system and hand over a signed BS 7671 electrical safety certificate. In addition, you should be sent a Building Regulations compliance certificate for all notifiable work by the operator of the registration scheme.


Properties dating from the 1970s or earlier that still have their original wiring, will now be overdue for complete renewal. The first job normally involves routing all the cables and fixing the backing-boxes in place. This is known as ‘first fix’. The ‘second fix’ stage involves fitting all the covers to the switches and sockets, and installing light fittings and ceiling roses etc.

Rewiring an occupied property is more difficult than in new construction, especially in flats, where cables are often buried within inaccessible floors or ceilings. So re-wiring can cause considerable disruption and expense. Traditionally, cables running along masonry walls would be buried in channels known as ‘chases’ gouged out of the walls. In new construction cables can be run behind flat steel shields which are pinned to the bare walls and then plastered over, or can be hidden within timber studwork walls.

Cables also normally need to be run through floors, which can mean drilling holes in timber joists to feed them through, but there are strict rules about how to do this without weakening the floor structure. When refurbishing a property, constructing a new false ceiling below the existing one can conceal lots of new cabling as well as improving fire and sound insulation. Similarly, dry-lining the main walls with plasterboard can create useful ducts for cables and wall lights whilst simultaneously boosting thermal insulation.

Alterations and improvements

If you want to upgrade your electrical system with some new switches, sockets or light fittings, it’s always a good idea to provide the electrician with a drawing showing the required positions. Common electrical improvements include:

Adding extra sockets

One of the most common complaints amongst house buyers is that there are insufficient numbers of power points for all the various gadgets that modern life demands. So extending a circuit to add an extra socket or two is a popular improvement when renovating. New cabling can be surface run in plastic conduit to avoid damaging decorations and cutting chases into walls, but this needs to be done neatly.

Depending on room size, a modern household requires about three or four DSSOs (double switched socket outlets) for each bedroom, five or six each for kitchens and living rooms and a couple for halls and landings. The Building Regulations now require that power sockets must be positioned no lower than 450mm above the floor, and light switches no higher than 1200mm from the floor. 

Fitting a new consumer unit

Installing a modern consumer unit (fuse box) is one of the simplest precautions to reduce the risk of electric shocks and fire. So if your old fuse box has ancient re-wireable fuses it should be replaced. Modern consumer units have MCBs (miniature circuit breakers) for each individual circuit. These automatically switch off or ‘trip’ when they sense a fault or overload, usually within 100 milliseconds, potentially saving lives. Modern ‘split load’ consumer units also provide additional RCD (residual current device) protection for the more vulnerable circuits (e.g. to outbuildings).

Safety testing

It is recommended that systems are tested every 10 years or upon change of ownership. To check the condition of your electrical system it’s advisable to arrange for a thorough electrical inspection and test by a qualified electrician, who will provide a test certificate. This is essentially an MOT for your home, and can be a lifesaver. It typically involves unscrewing and checking around 40% of all sockets and switches and lighting points in the house and takes several hours. This is followed by a series of tests carried out on the wiring as well as testing the insulation resistance to cables, and checking the circuits, consumer unit and RCDs.

Earth bonding

Many homes have electrical systems of 25-35 years of age which can still perform adequately with a spot of upgrading to bring them up to modern safety standards. This typically involves fitting ‘earth bonding’. Electricity will always head for earth the quickest way possible, including via any human body that happens to be in the vicinity. So in order to prevent possibly fatal electric shocks it makes sense to provide an alternative route. ‘Earth bonding’ protects occupants by connecting the metal components in the house with an earth wire (green and yellow sleeved). The requirement is to bond metal items such as incoming service pipes ( water, gas, oil and so on) as well as central heating pipes at the boiler, the hot and cold water pipes, and metal baths. New copper piping for heating and water needs to be earth bonded to the electrical system (but not where pipework is run in plastic).

Bathrooms and kitchens

When it comes to electrical work, any ‘wet rooms’ are high risk areas. So special care is needed when planning room layouts in kitchens and bathrooms so that nothing electric should be touchable from where a person could be in contact with water at the same time. In bathrooms a surprising number of electrical fittings may need to be accommodated, such as lighting, extractor fans, room heaters, shower units and pumps. However, only special low voltage safety fittings are allowed in bathrooms and no power sockets are permitted.

All electrical circuits within bathrooms must be protected by Residual Current Devices (RCD) not exceeding 30mA and there are rules that limit fittings to defined safety zones within the room. Light switches should be of the pull-cord type or else located on the wall outside the bathroom.


Another high risk area is outdoors. Many DIY power supplies run to garages and pond pumps and are potentially dangerous. This is why outdoor electrical work is now strictly controlled and circuits must be protected by RCD and cables must be run in special external grade protective conduit.


Although the Building Regulations are concerned with matters such as electrical safety and energy efficiency, they don’t normally apply where you’re simply changing bulbs or light fittings. However, for bigger renovation projects, such as adding a new bathroom, there are rules that need to be followed.