Sockets can be surface or flush-mounted. It's easier to surface-mount electrical fittings, but the flush-mounted versions look better and are less prone to accidental damage.
Before adding a socket to your electric circuit, you must ensure that it will be compliant with IEE electrical regulations, and establish whether the circuit will require RCD protection.
For your safety, these products must be installed in accordance with local Building Regulations. If in any doubt, or where required by the law, consult a competent person who is registered with an electrical certification scheme. Further information is available online or from your local authority.
Never take risks with electrical safety. Before you start any type of electrical work, you must follow these following safety precautions:
If the cable won't reach the terminals of the new socket without straining, don’t pull it. Use a specially designed crimp or terminal block to attach a new short length of cable. Only do this if there is room for it inside the mounting box - all wiring connections must be accessible and not buried in the wall behind.
If one of your sockets has been scorched, it's usually been caused by overloading or loose connections in a plug. Don't plug your appliances back in without dealing with the problem first or it will happen again.
Never take risks with electrical safety. Modifications to any circuit must comply with the latest IEE Wiring Regulations. New or replacement cables or sockets may need RCD protection.
Start by isolating the circuit. Use a socket tester to double-check that it's dead. Unscrew the socket faceplate and pull it away from the wall, but keep the screws in case the new ones don't fit.
Loosen the terminal screws and free the cable cores. If the insulation has been heat damaged, cut back the cores and strip the ends. Run green/yellow sleeving over the earth core if it's exposed. As the metal back boxes must be earthed, run a short length of earth cable between the earth terminals of the back box and the faceplate.
Connect the live core or cores to the live terminal (L) of the new faceplate, the neutral to the neutral terminal (N) and the earth to the earth terminal (E or (Earth symbol)). Fully tighten the terminal screws, and fit the new faceplate. If the new screws don't fit the lugs of the old box, just re-use the original screws. Finally, use the socket tester to check you've wired everything correctly.
If your socket is flush-mounted, it's very easy to replace it with a surface-mounted double socket. You can either get a special socket conversion box to help you do this, or use a standard double socket and drill and plug the wall (as shown here). If you want your socket to be flush-mounted, you'll need to take out the old box and make a larger recess for a new one.
If the cable won't reach the terminals of the new socket without straining, don't pull it. Use a specially designed crimp or terminal block to attach a new short length of cable. But only do this if there's room for it inside the mounting box - all wiring connections must be accessible, not buried in the wall behind.
First, you'll need to isolate the circuit. Use a socket tester to double-check that it's dead, then unscrew the faceplate and disconnect the cables from the terminals of the single socket mounting box. Run green/yellow sleeving over the earth core if you find it's exposed.
Next, remove the knockout in the new surface mounting box and pass the cables through. Then mark the fixing holes on the wall in pencil. Take the box away, check for hidden pipes or cables, and drill and plug the wall behind.
Screw the new box in place and connect the cables to the terminals. Fit the new faceplate, and use the socket tester to check it's correctly wired.
If you're flush mounting a box in a solid wall, you'll need to cut a neat recess through the plaster and into the masonry behind. This is dusty work, so it's a good idea to wear gloves and protective goggles.
Start by testing for hidden pipes and cables. If all is clear, hold the mounting box in position. Use a spirit level to check it's horizontal and draw its outline on the wall. Then, take a hammer action drill with a masonry drill bit and make a series of holes within the outline to a slightly greater depth than that of the mounting box. You can use a socket template to make this job easier, as this will guide the drilling of holes to hollow out this space. Set the drill's depth stop, or wrap masking tape around the bit as a depth guide.
Next, chop out the plaster and masonry with a bolster and club hammer, cutting down to the bottom of the drilled holes. Brush out all the debris and check the fit of the box.
Hold the socket box in place, mark the fixing positions, and drill and plug the holes. Cut a channel for the cable before attaching the box. Then isolate the circuit and make the final connections. Finish off by fitting the faceplate and using a socket tester to check the wiring is correct.
If you're flush mounting a socket in a stud wall, the easiest way to do this is with a cavity fixing box. This has a flange that sits against the face of the wall, as well as spring-loaded or rotating lugs that press against the back of the plasterboard. These give you more flexibility when you position the fitting.
Start by deciding where you want to put your new socket. If you have a stud finder, use this to check that none of the wall's framework will be in the way. If you don't have a stud finder, tap the wall gently with a hammer handle and listen for the hollow note to change when you tap over the framework. Hold the box in place, using a spirit level to make sure it's horizontal, and then draw around it in pencil.
Check the area is free of hidden pipes or cables. Then push and twist a screwdriver through at diagonally opposite corners of the outline so you can insert the blade of a pad saw or plasterboard saw. Cut outwards from the holes, following the box outline, and remove the waste piece of plasterboard.
After checking that the box fits snugly in the hole, remove the knock-out from it. Then push the box back into the hole, feeding the cable through the opening.
Push in or turn the securing lugs so they grip the rear face of the plasterboard firmly. Then connect the wires and fit the faceplate. Finally, check your socket is correctly wired using a socket tester.