Garden and Outdoor Electrical Work in NR5

Outdoor sockets, garden lighting, supplies to sheds, garden offices, detached garages and hot tubs. The technical spine is the same throughout: a circuit that leaves the house has to survive the weather and the occasional spade.

A supply to an outbuilding starts with the existing installation. The main fuse rating, the spare ways in the consumer unit and the earthing arrangement decide most of the cost. The submain is then sized for current and for volt drop over the run, and volt drop is what pushes the cable up a size on a long garden. Steel wire armoured cable goes in on a sand bed with warning tape above it, glanded at both ends, into a small consumer unit in the outbuilding.

Two things worth knowing. BS 7671 gives no burial depth for a domestic garden. Regulation 522.8.10 asks for armoured cable, marker tape or covers, and a depth that avoids reasonably foreseeable disturbance, which in practice means around 500 mm on a lawn and deeper under a drive. And where the house has a PME earth, exporting it to an outbuilding or a hot tub is usually not acceptable, so the outbuilding gets its own earth electrode.

Outbuildings, workshops, garden rooms and stables are all the same problem in different clothing: a sub-main out to a separate building, its own small board at the far end, and protection that suits a damp place people go into in wellies. Tell us what the building is for and we will spec it for that rather than for a spare bedroom.