Working from a shed with a 25 metre extension lead trailing across the lawn was a lockdown improvisation. Five years on, plenty of people are still doing it. Proper garden office electrics turn an outbuilding into a room you can heat in January, light in December, and fill with computer kit without a second thought. The difference between an extension lead and a real supply is about £700, a day’s work, and a certificate. Here is how the job should be done in 2026, and what it costs across the North West.

Why an extension lead is the wrong answer

A trailing lead to a garden building fails on three counts. Capacity: one 13 amp lead cannot run a 2 kW heater, a desktop, monitors, and a kettle together, and winter mornings demand exactly that combination. Safety: a lead crossing a lawn gets mowed, trapped in the door, and soaked, and most are not RCD protected at the house end. Insurance: a business policy for home working can be voided where the office runs on temporary wiring.

The Electrical Safety First garden guidance treats extension leads outdoors as a short-term tool for the lawnmower, not a permanent supply. A garden office used daily deserves the same standard of wiring as the house it sits behind.

What proper garden office electrics include

The standard job is a submain: armoured cable from the house consumer unit to a small consumer unit inside the office, usually buried at 450 mm or clipped along a boundary wall. The office board then feeds its own circuits, typically one for sockets, one for lighting, and a spare way for heating or future kit. Local RCBO protection in the office means a fault there trips locally instead of plunging the house into darkness mid-meeting.

Cable sizing is where DIY jobs go wrong. A 2.5 mm lead that felt fine in summer collapses under a winter heating load 20 metres from the house. A properly sized 6 mm or 10 mm submain costs little more and never gets thought about again. While the trench is open, it is worth pulling a data cable through too, because Wi-Fi through two brick walls and a garden rarely survives video calls. Customers planning smart home upgrades often extend their systems to the office at the same time.

Lighting design deserves five minutes of planning as well. A single pendant in the apex creates screen glare all afternoon, while two or three dimmable downlights plus a desk-height wall light give a room you can work in at 7 am in December. An outside light over the door, switched from inside, turns the walk back to the house from a stumble into a stroll.

Certification, notification, and resale value

A new circuit to an outbuilding is notifiable under Part P of the Building Regulations, so the work must be certificated. A registered electrician issues an Electrical Installation Certificate covering the submain and the new circuits, and the job gets logged with building control automatically. Keep that certificate with the house paperwork.

This matters more than most owners realise. Estate agents now market garden offices as a headline feature, and buyers’ surveys flag uncertificated outbuilding supplies as a defect. A £700 certificated supply adds value; a mystery cable from a kitchen socket does the opposite.

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A £700 certificated supply adds value; a mystery cable from a kitchen socket does the opposite.

LCE Electrical site team

Costs for a North West garden office in 2026

A straightforward supply to an office 10 to 15 metres from the house, with a four-way consumer unit, six double sockets, LED lighting, and an outside light, typically lands between £650 and £1,100. Longer runs, hard digging, or a house board with no spare capacity add to that. A full house board upgrade, where needed, runs £450 to £700 on top.

Heating deserves a line of its own. A 2 kW panel heater on its own circuit costs pennies to install during the main job and keeps the office usable year round. Adding it later means another visit and another disturbance. The same logic applies to air conditioning, which more office owners are requesting after the last two hot summers. Our domestic installation work covers the lot in a single visit where the building is ready.

For owners weighing the spend, compare it against the alternative: a year of hot desk hire in most North West towns costs more than the entire electrical installation, and the office adds value to the house rather than draining a subscription.

Getting the order of work right

If the building is not yet up, the sequence matters more than the specification. Groundworks come first, so the trench and ducting should go in while the digger is on site for the base, even if the cable itself is pulled through months later. A length of buried duct costs a few pounds and saves re-digging a finished lawn. Mark the duct position on a photograph before backfilling, because memories fade faster than lawns recover.

Next comes the building shell, then first fix wiring before the walls are insulated and boarded, then the consumer unit, sockets, and lighting at second fix. Builders and electricians who talk to each other early avoid the classic standoff where the office is plastered before anyone has run a cable.

Think a few years ahead while the trench is open too. A spare way in the office board covers a future air conditioning unit, and many owners route power for outdoor garden lighting along the same run while the ground is already open. Adding capacity at build stage costs a fraction of returning for it later.

Frequently Asked Questions