Sheds, Garages and Garden Offices: Getting the Electrics Right
Across Deal, Sandwich and the wider east Kent coast, garden rooms and converted garages have gone from luxury to normal. Home offices, gyms, workshops, studios, hobby spaces — all of them need power, and all of them sit at the end of a cable running through wet ground, away from the house.
Outbuilding electrics are where we see more improvised, non-compliant work than almost anywhere else. Here is what a proper job looks like, and why it is worth getting inspected.
An extension lead is not a supply
We will start with the one that matters most. A domestic extension lead run down the garden to a shed is not a permanent electrical supply. It is not rated for it, it is not protected for it, and it is not designed to survive being buried, walked on, mown over or left in standing water. It is a genuine fire and shock risk, and it is uninsurable.
Every year we get called to outbuildings powered this way, often for years at a time. If that describes your setup, please treat it as urgent.
What a compliant outbuilding supply involves
A properly installed supply to an outbuilding is a new circuit, and that means it is notifiable work under Part P of the Building Regulations. It should be carried out by a registered electrician who can certify and notify it. Typically it involves:
- A dedicated circuit from the house consumer unit, correctly sized for the load you actually intend to run — power tools and heaters draw far more than a laptop and a lamp
- Steel wire armoured (SWA) cable, run underground at a suitable depth — as a rule of thumb at least 450mm under lawn and garden, deeper under driveways and anywhere vehicles pass — with warning tape laid above it
- Correct glanding and termination of the armour at both ends
- A small consumer unit inside the outbuilding, so the building can be isolated independently and circuits are protected locally
- RCD protection appropriate to the circuits and location
- Correct earthing arrangements. This is the technical bit that catches DIY installs out: where the house has a PME (TN-C-S) supply, exporting that earth to an outbuilding is restricted, and a separate earth electrode may be required instead
- Main protective bonding to any incoming metallic services
- Suitably IP-rated accessories — outdoor sockets and fittings need to be genuinely weatherproof, not indoor accessories in a plastic box
Skip any of these and you have an installation that may work perfectly well for years and then fail dangerously.
When does an outbuilding need an EICR?
- When you buy a property with an existing outbuilding supply. You have no idea who installed it, how, or when. Very often there is no paperwork at all.
- If you inherited a supply with no certification. No Electrical Installation Certificate means no evidence the work was ever done or notified correctly.
- If the outbuilding is part of a rental property. It forms part of the fixed installation and is covered by the same five-yearly landlord duty as the house.
- If you run a business from it. A garden office used commercially may fall under the Electricity at Work Regulations 1989, and your business insurer is very likely to want evidence of a safe installation.
- On a routine cycle. Outbuildings live a harder life than houses — damp, temperature swings, condensation, physical knocks in a garage or workshop. They deserve testing at least as often as the main house, and often more.
Insurance is the sting in the tail
If a fire starts in an uncertified, self-installed garden office supply, your insurer will ask who did the work and where the certificate is. “I did it myself” is a very expensive answer. Certification is not bureaucracy — it is the document that proves the installation was designed, installed and tested properly.
Planning a garden office or garage conversion?
Talk to us early, before the building goes up. Getting the cable route, the load calculation and the earthing arrangement decided at design stage is far cheaper than retrofitting once the slab is down and the landscaping is finished.
RA Smith Electrical handles new outbuilding supplies, upgrades to existing ones, and EICRs on outbuildings of every kind — from a basic shed light and socket to a fully serviced garden office.