Chapter 12: Electrical


Don’t get a shock by avoiding electrical planning, the information and guidance in this chapter will help to get you up to speed with the basics of electrical installations; including the mimimum allowable socket outlets per room, building regulation legislation, requirements for inspection, the practical aspects of planning electrical points, protection against electrical fires and cable installation.


If you have an extension to your home, you will need to comply with all of the Building Regulations for any work, including any new electrical works. Electrical work should be planned properly, not only for what fittings you might need, but also to prevent any problems or delays later. You will also need to comply with BS 7671 which requires that a new electrical installation ‘must be properly designed and installed for maximum safety, and suitably enclosed and separated by appropriate distances to protect against electric shock, burn or fire injury’.


All new electrical installations will need to be inspected and tested during installation to make sure they comply with the Building Regulations.

If you are doing the work yourself, you will need to speak to your local council’s Building Control department. They will look at what testing and inspection of your work is needed and may either assign a third party or inspect the electrics themselves.

If you are hiring a contractor, they will need to be registered with the self-certification scheme and they will be able to issue a BS7671 certificate after installation. You will still need to notify Building Control for inspection.


Before starting any electrical work you’ll need to think about what you actually need and where appliances will be positioned. Think about providing at least one fitted double socket per room for smaller appliances like CD players or hair dryers so you don’t have to have trailing extension cables on the floor.

From NHBC guidelines, a main bedroom will need 6 x 13A outlets and any other bedroom should have 4. 2 outlets should be provided on landings and hallways.

RCD Devices

A Residual Current Device (RCD) is designed to stop you getting a fatal electric shock if you touch anything that’s live. It can also give some protection against electrical fires, and is additional protection over and above what ordinary fuses and circuit-breakers can do.

All sockets and outlets must have an RCD fitted in accordance with BS 61008.

Electrical Outlets & Fittings

The position of any electrical fittings and outlets will need to be decided early on so that plans can be made for cabling inside stud walls, partitions and floors.

The Building Regulations require that low energy lighting is installed with one fitting for every 25m2 or one in every four fixed light fittings. You will also need to look at lighting for your new staircase and make sure that it falls on the treads for the clearest and safest illumination.

You will need to fit a mains wired smoke alarm, with either a battery back-up or a dedicated circuit, on each floor, and they should be interlinked so that if one alarm is triggered, every alarm sounds.

If you have added a bathroom/WC, you will have to include an extraction unit, and unless you use a passive stack system which doesn’t need power, you’ll need to make provision for this.

Check the Domestic Heating Compliance Guide for the minimum requirements for heating controls:


Your house is a domestic installation in terms of cabling which means that the standard cable colours can be used, i.e., brown is live, blue is neutral and earth is green/yellow.

You must have smoke alarms in your loft and they need to continue to operate for as long as they can if a fire breaks out so look at using fire resistant cable. This would also be the case if you have fitted emergency lighting.

Cables should not be placed near or inside thermal insulation unless they are the correct size as insulation can reduce current carrying capacity. Cables without any special protection have to be positioned not less than 50mm below the wall surface and not less than 50mm from the top or bottom of a batten or joist in a floor or ceiling. They should also be positioned vertically or horizontally from the socket.

County Lofts are fully certified electricians, so for further advice, give us a call on 0800 046 1995.