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Getting Electrics to the Garage

By: Chris Hogan MSc - Updated: 30 Mar 2016 | comments*Discuss
 
Garage Electrician Catenary Support

In a modern house it's very common to have lighting and power sockets in a garage but an older house might not be so well equipped, particularly if the garage is detached. This article will explain the issues you will face if you want to get electrics to a garage or other outbuilding.

You Must Use an Electrician

The main issue is that you will have to employ an electrician, for the connecting up and testing at least. Changes in recent years to building control regulations make it prohibitively expensive for anyone other than a fully qualified and certified electrician to do anything more than changing internal fittings.

But that doesn't mean you can't do the rest of the donkey work yourself and save money. You'll need to make sure that there is a spare slot in your consumer unit or distribution board (or fuse box in old money) to take the supply as it must have its own supply. It will need a residual circuit breaker (RCD) at the consumer unit which will cut the supply as soon as it detects anything untoward.

Digging for Glory

The second stage, where again you can save cash, is getting the cable over to the garage. This will most likely mean digging a trench across to it, as the safest way to run the cable is underground in armoured conduit. If that's the solution it doesn't really make a great deal of sense racking up an electrician's expensive hours to dig holes.

The other tricky bit is getting the cable out of the house, and this depends on where the consumer unit is in relation to the run to the garage. If it's a long way you might want to run the cable inside the house, under floorboards, before breaking through the wall.

The alternative is running the cable around the outside of the house, pinning it to the wall. Which one you choose really depends on your house layout, which method is easiest, and your preference.

Keep Up the Suspense

Sometimes it's easier to run an overhead cable, again it depends on the situation at your house. It you do go down this route, the cable will have to be suspended securely, it's not enough to just throw the cable across. You can put up a wire secured by brackets on the house wall and at the garage end, and suspend the cable from that. This is known as a catenary system.

Or you can put solid conduit across and run the cable through that. Currently the height limit is at least three-and-a-half metres from ground level, whether you use solid conduit or a catenary system, so make sure you have a decent ladder. This also means the catenary fitting at the garage end will probably have to be on a pole, like a television aerial support, to get it high enough to meet regulations.

Sorting Out the Garage End

Once you have sorted out how to get the cable to the garage you then need to get it inside. Hopefully this will be a lot easier than with at the house end. Garage walls aren't as thick as those for the house, they are out of the way, so looks aren't as important, and you can pretty much decide where the consumer unit will go, all of which makes the job a lot easier.

Yes, that's right, you'll need a consumer unit at the garage end as well, sorry. Even if it isn't required by regulations (which it almost certainly will be) it's the neatest way of terminating the cable. The electrician can then connect up lights to one slot and power to another, with spares available for future use.

In the garage you can again do the donkey work but not the connecting up. So you can run the cables to the lights and sockets you want and even put up the consumer unit, lights and sockets. But the electrician has to connect it all up and test it before you can use it.

Work it All out With the Electrician First

The best approach to this is to get an electrician in at the outset, discuss what you want and say that you want to do as much work yourself as possible. The electrician will talk about your requirements and tell you what thickness and standard of cable you need for the main run, and what capacity consumer unit to get for the garage. Make sure it's all enough for potential future use, not just for your immediate needs.

Then you can arrange a time for the electrician to return to connect it all up, leaving you to do all the basic work. As long as you follow what he tells you to do there shouldn’t be any problems.

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Hi I noticed in this article you suggest the homeowner "can run the cables to the lights and sockets" however this is prohibited under BS7671 as the electrician is responsible signatory for the design, installation, inspection, testing and certification. If he didn't run the cables he cannot sign for the installation. For example how does the electrician know the householder hasn't chafed cable insulation or place cables over a old nail end etc. (behind the cable so it is not visible when fixed). This is not a far fetched scenario as I have seen it done (and much worse) by diy enthusiasts many times. Whilst the installation is tested thoroughly it cannot always reveal mechanical damage as a defect in early stages, which may not become apparant until longer term under load. If the garage burns down who will the insurance persue? Who signed the certificate?
alan davies - 30-Mar-16 @ 8:26 PM
I was hoping this article would answer this: The electrician will talk about your requirements and tell you what thickness and standard of cable you need for the main run, and what capacity consumer unit to get for the garage.
ChrisB - 1-Feb-16 @ 11:57 AM
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