Garden room electrics: power from the house

Why this is not a DIY job

Electrical work in a garden room is covered by building regulations in England. The Planning Portal says that electrical work in your home, garden, garage or shed must meet them. Part P is the section that covers it.

Even when the room itself is exempt from building regulations, the electrics are not. A small garden office under 15 m² still needs the supply done properly.

What counts as notifiable

• A new consumer unit (fuse box) is notifiable.
• A complete new circuit is notifiable. A garden room fed from the house usually needs one; your electrician confirms this for your build.
• Adding to an existing circuit is only notifiable in special locations. In England these are the spaces around baths and showers.
• A registered electrician can self-certify. Otherwise building control or a registered third-party certifier must be told before work starts.

The Planning Portal gives the examples. A new consumer unit is notifiable. So is a complete new circuit, such as a lighting, ring or shower circuit.

How power gets to the room

Your electrician plans the route from the house. They will advise on the cable, the way it is protected and buried, and the protection at the house end. We do not give those details here because they depend on your site and on the current wiring rules. Ask for a written design.

• Walk the route with the electrician. A long run costs more.
• Agree where sockets, lights, heating and data points go before the build, not after.
• Ask about outdoor lighting and a switch for the whole building.
• Think ahead. A room that starts as an office might later take a heater or air-con. See heating and air-con.

Work out what you will plug in

List everything the room will run before you meet the electrician. A desk set-up is a small load. A heater, an air-con unit, a kettle and a treadmill are not. The more you list, the better the electrician can size the supply and the protection.

• Computers, monitors, printers and a router.
• Lighting inside, and lighting on the path to the room.
• Heating or cooling.
• Gym kit, audio kit or studio lights.
• An outdoor socket or an electric vehicle charger is a separate question. Raise it now if you want one.

Broadband matters too. A wireless signal can struggle to reach the end of a garden. Ask the electrician about a data cable in the same trench, or a wired access point in the room. It is easier to do while the ground is open.

Timing

Electrics usually happen in two stages. The first stage goes in while the building is open, and the second once the walls and floor are done. The Planning Portal says to notify before work starts. Ask the builder when the electrician is booked, so the schedule does not slip.

Who can do the work

The Planning Portal recommends an installer registered with a competent person scheme. They can self-certify that the work meets the regulations. If the installer is not registered, the job must be inspected by a building control body or, in England, a registered third-party certifier.

Notify the relevant body before work starts. Do not wait until the end.

Paperwork to keep

• The electrician's certificate for the new work.
• The building regulations certificate or notice, if one was issued.
• A circuit list or diagram, so the next electrician can see what feeds what.

You may need these when you sell the house, or if you insure the room. See does a garden room add value.

Annexes and wet rooms

The special-location rules in England cover the space around baths and showers. If your room has a shower, the electrics are stricter. An annexe also needs full building regulations. Read garden annexe rules and building regulations for garden rooms.

Questions for your builder

• Is the electrical work in the quote, and who does it?
• Are your electricians registered with a competent person scheme?
• Will I get a certificate?
• What is not covered, for example digging a long trench?

Electrics change the price. Use the garden room cost calculator and read how a price is built. Local builders in St Albans, Chesham and Hemel Hempstead handle this every week. See also garden studios.

Common mistakes

• Hiring an unregistered electrician. The job then needs inspection by building control or a registered third-party certifier.
• Starting before notifying. The Planning Portal says to notify before work starts.
• Not asking for the certificate. Without it you cannot prove the work was done to the rules.
• Too few sockets. Adding them later is harder than planning them now.
• Leaving the trench to chance. Agree who digs, who backfills and who reinstates the lawn.

If you are unsure whether your plan counts as notifiable, the Planning Portal advises contacting your local building control department.