Summary: Learn how to run cables under floors, run cables parallel to joists, run cable at right-angles to joists and run cables in stud walls.
Things can and will go wrong during any home renovation project. Before picking up your tools, check the basics first, double check your home content insurance policy and, as always, if you’re completely unsure hire a professional.
Electrical cables can be surface-mounted, fixed to skirting boards or architraves with clips or fixed to walls and concealed with self-adhesive mini-trunking. To conceal wiring completely, you will have to bury it behind walls or under the floor.
When deciding where to put power sockets and fittings, trace the path of existing cables and plumbing pipes using a cable-detector and pipe-detector. You may need to gain access to the joists to locate the main circuit cable.
Cables should be run along the ceiling void or under the floor to a point directly above or below the switch or appliance outlet and never run diagonally across walls to reach the switch.
Light fittings and junction boxes will need to be positioned on one side of a joist or stud to secure them to the timber structure but switches, sockets etc. must be between joists or studs.
If you have concrete floors you must conceal cable in the walls, as cutting into the floor risks damaging the damp proofing and any buried pipes.
There are two methods of securing cable to the joists: you can either run the cable parallel with the joists, fixed to the side of the joists or drill holes in the joists and feed the cable through them at right-angles.
Fix the exposed cable to the joist at regular intervals using 50mm clips.
Replace the floorboards and mark them to show where the cable lies.
If you are building a new stud wall, you can run cable between the sheets of plasterboard. To protect the cable, you can thread it into a PVC conduit as used in masonry walls.
Dropping a cable behind existing stud walls may be possible if there are no horizontal noggings or blanket insulation to block the path of the cable.
After drilling a hole in the timber head or sole plate, pull the cable through.
Plasterboard the other side of the stud wall, cutting a hole where the cable needs to exit and pull it through.
Drill a hole through the head plate and feed the cable down behind the stud wall.
Cut a hole in the stud wall to retrieve the cable.
A groove cut into a masonry wall to accommodate wiring is called a chase. Before you cut out a chase to house the cable, use a cable detector and pipe detector to locate any other cables and pipework behind the walls. If existing wiring is near to where you want to run a new cable, cut off the power supply at the consumer unit before carefully cutting out a chase.
After drilling overlapping holes place a bolster chisel into the grooveand tap it with a club hammer to chop out a chase.
Secure the conduit with galvanised nails.
Whether your new cable route is to supply a switch, socket or other outlet, you will need to fix a mounting box or plate to the wall to house the connections. To make a hole in the ceiling for a ceiling light flex or to install a light fitting mounting box, see the section on installing light fittings.
If using a metal mounting box place a grommet around the entry hole to protect the cable.
To finish, plaster over the chase and around the mounting box .
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The colour-coding system for electric cable changed in 2006, make sure you read Electric cable and flex to view the new information.
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