Working from a garden office, garden room or annexe? We run a SWA armoured submain from your house CU to a sub-board with its own RCBO bank — then wire the sockets, heating, lighting and Cat6 data your workspace needs. One visit, one trench, fully certified. From £680 + VAT @ 20%.
07889 334849 · Dan Stevens
NAPIT
City & Guilds
TrustMark
Part P
BS 7671A garden office submain is the wrong job to under-spec. Cable size depends on both load and distance — not just one. A panel heater running all winter, a desk full of monitors and the kettle all add up. We calculate volt-drop on the actual route and pick a cable that runs cool, lasts decades, and leaves headroom for what comes next.
Laptop-and-lamp use. Lighting circuit, a couple of double sockets, no fixed heating. Sub-board with 2–4 way RCBO bank.
The work-from-home standard. Socket radial, dedicated heating circuit, lighting, Cat6 data in the same trench. 4–6 way sub-board.
Larger garden rooms, annexes and 25–40m runs. Air conditioning, kitchenette loads, EV charger headroom. 6–10 way sub-board.
Wired network back to the house router, run alongside the SWA in its own conduit. Rock-solid video calls. Outdoor wireless link where a cable run isn’t practical.
Real DS Electrical install — metal-clad socket and fused spur in a timber outbuilding.
Whether it’s a small studio on a short run or an annexe at the bottom of a long garden, the standard is the same. Compliant cable, correct RCBO, sub-board, full test pack, Part P notification.
Steel-wire armoured, glanded both ends, buried at depth with marker tape or surface-clipped. Never T&E for submain runs.
Full-RCBO consumer unit in the office. One RCBO per circuit. A heater fault doesn’t take out your desk.
Socket radial where the desk goes, dedicated heating circuit, office lighting and outside lights for the walk back.
Cat6 in separate conduit, same trench. Wired internet for video calls that don’t drop. Outdoor wireless link where trenching isn’t on.
Submain upsized once at design stage; future charger lands on its own Type A RCBO at the sub-board. One dig, two outcomes.
Electrical Installation Certificate, Part P notification lodged via NAPIT. Both by email within 7 days.
Final price depends on run length, dig conditions, cable size, sub-board ways and fitting count. Survey is free; written quote is fixed. Read the disclaimer below the cards before assuming.
Most of our garden office installs combine the SWA submain, a sub-board, heating and socket circuits, and Cat6 data into a single visit. We design the submain to leave headroom for future loads — so you don’t pay to dig the garden twice.
A dedicated SWA (steel-wire armoured) submain from your house consumer unit to the garden office — buried at correct depth with marker tape, or surface-clipped where digging isn’t practical — feeding a small sub consumer unit inside the office. From the sub-board we wire the circuits the room needs: sockets, lighting, heating, and data. Everything is tested, an Electrical Installation Certificate is issued, and the work is Part P notified via our NAPIT registration.
It depends on the maximum demand and the run length. A lightly loaded garden studio within around 20 metres is often fine on 4mm² SWA. A working garden office with a panel heater, desk equipment and lighting typically wants 6mm². Long runs or heavier loads — air conditioning, kiln, EV charger headroom — push you to 10mm² or beyond. Volt-drop on the actual route decides it; we calculate it at the survey rather than guessing.
Yes — and the trench is the cheapest place to do it. We run Cat6 data cable in its own conduit in the same trench as the SWA supply, giving the office a wired network connection back to the house router. Far more reliable for video calls than Wi-Fi across a garden. Where a cable run isn’t possible we can fit a proper outdoor wireless link instead — see our Wi-Fi access points page.
Yes, if the submain is sized for it on day one. If the route passes near your parking, upsizing the cable at install time is a small uplift compared with digging the garden twice. The EV charger then sits on its own Type A RCBO at the sub-board — BS 7671 requires Type A on EV circuits. Tell us at the survey and we’ll spec the headroom in. More on our EV chargers page.
Yes — a new submain and new circuits are always notifiable under Part P of the Building Regulations. We notify automatically through our NAPIT registration; you don’t need to apply separately. You receive an Electrical Installation Certificate plus the NAPIT compliance certificate, accepted by insurers, mortgage lenders and surveyors.
Spec this job on a 3D model of your property — real products, down to the socket finish — and DS Electrical Installations quotes it to your exact specification.
Power, heating, lighting and wired internet — specced once, dug once, certified once. If a future EV charger is on the horizon, we’ll size the cable for both. Free survey, fixed quote, NAPIT certified.
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