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Come to Life!
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In most cases, the power to your garage, shed or garden cabin is running on indoor twin and earth cable that was never designed to live outside, and it\'s now carrying far more than it was ever sized for. The permanent fix is a new SWA (steel wire armoured) cable from the house to a small dedicated consumer unit in the outbuilding, with lighting and power on separate, RCD-protected circuits.
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If your garage or shed power has started tripping out, or just died completely, I can almost guarantee what we\'ll find when we get there: a cable that was never meant to be there in the first place.
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We get called out to this constantly. The homeowner tells us \"it\'s worked fine for years\", and it has, right up until it hasn\'t. Here\'s what\'s usually going on, and what fixes it for good.
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A failing outbuilding supply rarely dies without warning. The usual signs are the RCD tripping when it rains or after a cold, damp night, the power cutting out when the freezer, heater or a power tool kicks in, lights flickering or dimming, sockets that are warm, discoloured or smell of burning, and cable on the outside wall that looks cracked, faded or brittle. If you\'re seeing any of these, the cable feeding the building is the first thing we\'d check.
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Years ago, a single socket and a light in the garage or shed didn\'t ask much of a cable. A thin feed run off an existing indoor circuit was enough. Somewhere along the way, often before the current owner even bought the house, someone added another socket. Then a freezer went out there. Then power tools, a heater for the colder months, maybe a garden office kitted out as a proper workspace.
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None of that got planned as a whole. It got bolted on, one job at a time, onto a cable that was only ever sized for a lamp and a kettle. Think of it like a garden hose that was fine for watering a few pots, now being asked to fill a pond, run a sprinkler and wash the car at the same time.
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Garage interior with an additional socket, for a freezer
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Lighting adds to this more than people expect. What started as a single pull-cord light often ends up with extra fittings inside the garage, plus a security light or PIR floodlight outside on the same feed. Security lighting in particular tends to go in as an afterthought, wired off the nearest handy point rather than treated as another load on an already stretched circuit. On its own it\'s not much current, but it\'s one more thing pulling from a cable that was never designed for any of this, and one more connection point exposed to the weather.
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Security light on Front of Garage
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No. Standard twin and earth (T&E) is designed for dry, protected runs inside a building: under floors, in walls, through loft insulation. It has no armour, and its PVC outer sheath isn\'t built to survive years of UK weather.
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We regularly find it clipped straight to an outside wall, running through flower beds, or buried a few inches down with no protection at all. UV breaks down the sheath, moisture gets in, and the insulation degrades from the outside in. Add a growing load on top of a cable that\'s already failing, and something eventually gives. Usually that\'s nuisance tripping first, then total loss of power.
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For an outdoor run we use SWA (steel wire armoured) cable, sized for the load and the distance. Voltage drop matters more the further you go, so a garden office at the bottom of a long garden may need a heavier cable than a garage next to the house.
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SWA is buried at the correct depth with warning tape above it, or clipped and protected properly where it has to run above ground. The steel armour protects it from spades, forks and rodents, and the outer sheath is made to sit outside for decades without breaking down the way T&E does.
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Left: twin and earth, built for inside your walls. Right: SWA, built for outdoor and underground runs.
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SWA cable in a garden trench with warning tape before backfilling
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If you\'re running more than a single socket and a light, yes. A small dedicated consumer unit in the garage or cabin, fed by one SWA cable from the main consumer unit in the house, gives every circuit out there its own breaker and RCD protection, instead of everything hanging off one overloaded feed.
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It also means future additions, whether that\'s another socket, a heater or an EV charger, get added properly at that board rather than daisy-chained onto whatever\'s already struggling.
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This is also the point where we sort out the earthing. A supply that leaves the main building has to be earthed correctly for the type of supply your property has, and on older setups it\'s often been overlooked completely. Sometimes that means installing a separate earth rod at the outbuilding. We\'ll assess it at survey and explain what your property needs.
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A dedicated consumer unit at the outbuilding. Lighting and power on separate, labelled, RCD-protected circuits.
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We start with a survey. We test the existing supply, find out everything that\'s connected, and ask what you want to add in the next few years. That tells us the cable size, the route and whether it needs burying or can run along a wall or fence.
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Then we run a fresh SWA cable from the consumer unit in the house to a new small consumer unit in the garage or cabin. Whatever\'s currently connected, including sockets, lighting, security lighting, freezer and heater, gets split across properly rated circuits at that new board, each on its own breaker. Lighting and power always end up on separate circuits, so a fault on one doesn\'t leave you in the dark. Finally, we test everything, notify the work under Part P and give you your certificate.
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It\'s more work than patching the existing cable. But patching an inadequate feed just delays the next callout, and we\'ve seen the same property come back once one more appliance gets plugged in. Next time it\'s usually an emergency.
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Yes, often more so. Landscaping and garden maintenance firms, small manufacturers and businesses with storage units or workshops in outbuildings tend to have heavier loads out there: battery chargers, compressors, heaters and power tools running all day. The same fix applies, designed for commercial use, and we can PAT test the equipment while we\'re on site.
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The price is driven by three things: the length of the cable run, whether it\'s buried or surface-run (digging is the biggest variable), and how many circuits you need at the far end. A garage attached to the house is a very different job from a garden office 40 metres away across a lawn and a patio. We\'ll always survey first and give you a clear, itemised quote before any work starts. No guesswork, no surprises.
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Not if it\'s twin and earth run outdoors. That cable is the problem, not a coincidence. It needs replacing with SWA (steel wire armoured) cable, sized for what\'s connected out there now, and what you\'re likely to add, rather than what was connected when the cable was first run.
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Weather damage to cable is gradual. The sheath copes at first, then UV and moisture break it down from the outside in. Meanwhile more load gets added over the years. Eventually one more appliance, or one wet winter, tips it over and the RCD starts tripping or the power goes altogether.
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Yes. A new circuit to an outbuilding is notifiable work under Part P of the Building Regulations. As NICEIC-registered electricians we self-certify the work, notify it for you and issue an Electrical Installation Certificate when it\'s complete.
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It can, but it has to be designed in from the start. An EV charger changes the cable size, the load calculation and often the earthing arrangement for the whole supply. Tell us at survey if a charger is on the cards, even if it\'s a year or two away.
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Deep enough that it won\'t be disturbed by normal digging. Typically that\'s around 500 to 600mm under lawns and borders, and deeper where vehicles cross, with warning tape laid above the cable. Where it can\'t be buried, it\'s clipped and protected along walls or fences instead.
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Don\'t keep resetting it. An RCD that trips repeatedly is telling you current is leaking somewhere it shouldn\'t, often through damaged cable insulation. Switch the garage circuit off at the consumer unit, and if you can see cracked or perished cable, a burning smell or scorched accessories, leave it off and get it looked at.
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If your outbuilding power keeps tripping, or you know it\'s running off an old cable like the one in the photos, get it looked at before it fails completely. That\'s always at the worst possible time.
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I\'m Karen Smith, owner and electrician at Bright Spark Electrical Services, with over 25 years\' experience. My team of NICEIC-registered, qualified and insured electricians cover a 25-mile radius of Tonbridge, Tunbridge Wells, Sevenoaks and Crowborough, for homeowners, landlords, care homes and businesses.
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We aim to attend emergencies the same day, with small works typically booked within one to two weeks and larger projects within three to six weeks.
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Call us on 01892 531 728, email karen@brightsparkelectrician.co.uk, or request a quote online.
This company was recommended by some people on the Nextdoor website. I wanted new lights installed in my kitchen, dining room and conservatory. Karen got back to me within minutes of my email and both Electricians proved to be efficient, friendly and tidy workmen. I will be keeping their business card handy for future use.
We are very pleased with Phillip’s work. You’ve truly gone above and beyond to deliver what we had in mind for our front porch.
Phil, from Bright Sparks arrived promptly, was really polite, cracked on with his job and gave us a really good brief on what he'd done and why it was needed which was then followed up with a thorough report. Bright Sparks have been absolutely superb and not only are they saved in my phone but also I'd recommend them to friends and family. Thanks guys. P.s. you were up front and transparent about costs too.
Karen runs a great company. She is that very rare breed of taking care, respecting and rewarding her employees. In turn, Terry who carried out our work showed due care and attention and completed works with such professionalism. He interacted with my inquisitive little boy who may, one day may, become an electrician - he certainly had a great role.model to follow!
My external security lights had failed and because they were over 20 years old, several electricians felt unable to help me. I then asked Karen from Bright Sparks to get involved. She promptly surveyed the problem, gave me a competitive quote and as soon as I accepted it, gave me a firm date for the work to be undertaken. Her electricians arrived on the due date, were very friendly and tidy and worked in difficult places without problem. I definitely intend to use Bright Sparks again.
