|Cabling How To|
Getting cables though the walls of your home can be a little tricky, here are a few tips to help make it easier.
Firstly running cables in you home and working in the roof can be dangerous to the DIY cabler and also may create safety hazards for other people in the future. Always consider the safety issues surrounding a job carefully before starting work, if you have any concerns about the safety of what you're doing get a professional to do it.
The most obvious safety risk associated with cabling in the home is the presence of electrical wiring in the walls and roof. Firstly you should confirm that your home is fitted with an electrical safety switch, all new homes are now required by law to have one fitted, if your home does not have one then we recommend you contact a registered electrical contractor and have one installed before doing anything else. A safety switch will detect a fault by comparing the current flow in the active and neutral wires of the electrical supply. Any difference in the current indicates a leakage from the electrical circuit to earth (possibly flowing through a human body) and the safety switch cuts off the power supply before any damage can be done.
Though a safety switch should save your life in the event that you come in contact with electrical wiring it's best not to test it. The safest thing is to turn off the power at the main switch before starting work, don't just isolate the circuit you think is the one you are working near as it's too easy to turn off the wrong circuit. If you need to use mains power tools then you should take extra care to avoid any wiring.
Before cutting or drilling into a wall take a look around for any power points and electrical fittings near by (check both sides of the wall if appropriate). The electrical wiring should run from the outlet or fitting up the wall to the roof but may not be in direct line with the outlet. Some stud finders have a wiring detection function, these only work if there is current flowing though the wire so you need to use them before turning the power off and supply a load (eg. plug a lamp into the power point and turn it on). In any case you shouldn't trust these devices 100%, always turn the power off.
Always make sure the ladder you're using is sturdy, in good condition and properly suited to the job, have somebody hold the ladder for you when climbing onto or off the roof. If you have mud on your shoes make sure you scrape the mud off before climbing the ladder or onto the roof.
Working in the roof of a house can be very hot even on mildly warm days, always make sure you drink plenty of water, if you feel sick or weak or have a headache you should stop work immediately and cool down. TIP: you can usually open some tiles in the roof (if they're not nailed or wired down) from the inside, this will help cool air flow though the roof while your working there, this also allows you to see a lot better, just remember to close them again when you finish.
Firstly you should think through and plan where you are going to run your cables before starting work, take into account where devices will be mounted and what obstructions might be in the way, you don't want to have to patch up holes in the plaster because you put something in the wrong place.
Once you have identified where the cables are going to run and identified where any electrical wiring is you need to get the cables into the wall. Use a stud finder to locate the studs near where the cable will run, putting the wall plate or outlet near a stud might make it easier for you to get the cable down the wall. Keep a minimum distance of 150mm from any power outlet or fitting, the cable must not run within 50mm of any electrical wiring in the wall. Cut a rectangular hole in the plaster where the wall plate will be fixed, you can use a plaster saw for this or a sharp knife.
If running the cable through the roof then you will need to be able to find the exact point directly above the hole. The best way to do this is to measure from the center of the hole to a fixed point in the room, an outside wall is the best thing otherwise measure to another wall that can be easily identified. Take note of the buildings features before climbing up into the roof (things look a lot different up there). Once you have identified the correct wall in the roof you need to drill a hole in the top plate (wooden beam that forms the top of the wall). Measure from the same point (eg outside wall) to find the point directly above the hole you made. You should be able to see where the studs are, look for the nails.
Once you have drilled the hole you will need to drop something down to pull the cable through. The best tool for this is "yellow tongue", this is the tongue from tongue and grove flooring and is perfect for getting cables through the wall. You may be able to get some for free if you know someone in the building trade or ask at the hardware store, otherwise you can buy some. Drop the yellow tongue straight down the wall cavity (as straight as possible) on one side of the wall or the other, in most new homes there is a cm or so gap between the plaster and the noggins that you must get the tongue through.
If you home is an older building then there may be no gap between the noggins and the plaster, or the cable you are running may be too big to fit past the noggin. In this case you will need to drill though the noggin using a drill bit on an extension. This can get a little tricky and expensive if you need to buy the extensions. Getting the yellow tongue through the second hole can be very challenging. TIP: drill a second hole in the top plate so you can shine a torch down.
Once you have the yellow tongue down the wall go down and look through the hole to see if you can find it. If you have measured accurately (or are very lucky) it will be right there (get a torch and have a good look around). If not you will need to do some fishing, for this I recommend some plastic coated gardening wire. Only use plastic coated wire (for insulation) and make sure you tape up the end so you can't come in contract with the bare wire, of course the power should be turned off but this is an extra precaution. Make a hook from the wire and start fishing around for the tongue.
When you have found the tongue you can then push it up the wall until you see the end, then guide it though the hole. Now you have the tongue through the wall you can either tape the cable directly to the end of the tongue and pull it through or tape some sturdy string to the tongue and pull that through. You can then use the string to pull through several cables (TIP: tape the cable to a knot in the string and pull some string though with the cable, that you you can pull the string back though later), you can even leave the string in the wall in case you need to pull more cables through some other time.
If you need to get cables down an external wall to the outside of the house then it's going to be a little more difficult. Firstly drill through the mortar between the bricks and open up the hole so it's a few cm wide. Then you need to take some tiles off the roof and push down the yellow tongue. You won't be able to get the yellow tongue through the hole so tape a loop of string to the end of the tongue with a small amount of tape (so that the loop can be pulled off). Then get someone to help you with hooking that loop with some wire as it's near the hole in the brick work. It might take a while to get the loop in the right position and it might be hard to get the tongue down if there is a lot of excess mortar in the cavity.
Running cables in the roof
When running cables in the roof they do not need to be fixed but should be out of the way and not present a tripping hazard. You should maintain at least 50mm space between any cable and power cables or pipes, if this is not possible there must be a durable barrier in between. If you must run the cable across a power cable you can run it through a short length of flexible conduit where it crosses the power cable or pipe, tape the conduit to the power cable to keep it in place.
Running cables to a wall mounted TV
If you are only running cables up the wall to a wall mounted television then your job should be easier. There are however some additional considerations.
Before mounting any wall plates or making any holes mount the wall bracket first or mount it temporarily and mark where the holes and edges are, that way you won't put the wall plates in the wrong place.
Be careful to make sure you have the bolts in the center of the studs (big screens can be heavy). Mark the center line of the stud and confirm you have the center by probing either side with a short nail.
You may need to run several cables to the screen so it may not be possible to get all of them past the noggin, at best it will make it difficult to get the cables through. You should be able to identify where the noggin is with a stud finder. It may be possible to mount the wall plate/s below the bracket (but still behind the screen) in such a way that it's below the noggin. Otherwise if you put the wall plates just above the noggin you may be able to drill through it on an angle. If not you may need to cut a large hole in the plaster so you can drill straight through the noggin and patch it up (it should be covered by the screen anyway).
Due to wiring rules it is illegal to run a power cord or extension cord through the wall, for this the best option is to have a power point installed behind the screen.