IP rating + fittings
BS EN 60529 IP rating: first digit = solids (dust); second digit = liquids (water). Outdoor minimum: IP44 (splash-proof) acceptable for sheltered patio (under canopy); IP55 (dust-protected + low-pressure jet) standard exposed garden socket + light; IP65 (dust-tight + low-pressure jet) preferred sockets exposed to weather; IP66 (high-pressure jet) outdoor in coastal or driveway car-wash zone; IP67 (immersion 30min) underground junction or below DPC; IP68 (continuous immersion) pond/pool/below-water. Outdoor socket: IP55/IP65 weatherproof flap (BG WP22, MK Masterseal — £15–£45 per double socket); height 450mm above paved level; RCD-protected from CU (mandatory). Outdoor LED downlight or wall-mounted spotlight: IP65 typical (Saxby, Knightsbridge, Astro outdoor range); 5W LED replaces 50W halogen; warm white 2700K typical for garden (cooler 4000K for security floodlight). Bollard / pillar light (1m high path light): IP65 + impact-resistant — JCC Toughpath, Saxby Equinox. Underwater pond light: SELV 12V via transformer outside water, IP68 fitting submerged.
Cable + circuit design
Steel-Wire Armoured (SWA) cable: standard buried + external use — 2.5mm² for lighting circuit, 4mm² for socket/garage feed, 6mm² for garden-office sub-main, 10mm² for granny annexe 60A sub-main. Burial depth 450mm minimum (general garden) or 600mm under driveway/heavy traffic; sand bed 100mm + cable + sand cover 100mm + warning tape (yellow 'Electric Cable Below') + topsoil/paving. Alternative: 25mm PVC conduit at shallower depth (still 350mm+ minimum) where SWA buried impractical (paved areas). Cable joints: outdoor weatherproof junction box (IP65 enclosure with cable glands) — never tape joints buried. Circuit: dedicated radial from CU (NOT ring extended to outdoor — outdoor faults trip indoor sockets); typically 16A RCBO for garden lighting + sockets; 32A RCBO for garden office sub-main; separate 16A RCBO for hot tub / external charger / shed power. 30mA RCD protection mandatory all outdoor circuits. Earth: SWA outer armour serves as cable circuit protective conductor (CPC) — bonded at both ends with brass gland; additional internal CPC for additional earth path. Garden building sub-main: terminates at sub-CU (small consumer unit, 2-way or 4-way RCBO) inside building; sub-CU distributes lighting + sockets within building. Class II earthing arrangement (no need for TT earth rod if PME bonded from main CU — confirm with installer).
Process + compliance
Building Notice: outdoor electrical work classed as 'special location' for purposes of Part P + competent person registration — installer NICEIC/NAPIT/ELECSA notifies via competent person scheme. New circuit / new sub-main / hot tub / pond / pool: all notifiable. Quote breakdown: cable + glands + sub-CU + RCBO £350–£950; trenching + reinstating £450–£1,200 typical 15m run; outdoor fittings + sockets £185–£650; commissioning + certificate £85–£185. Garden office wiring spec: lighting (4–6× 5W LED IP44 ceiling) + 6× 13A sockets (2 wall + 1 work top + USB) + heating circuit (electric panel heater 1.5kW) + comms (Cat6 from house router) — typical £950–£1,800 sub-CU + first-fix + second-fix. EV charger external: see [[ev-charger-load-management-london]] for dedicated detail. Hot tub: dedicated 32A RCD circuit + isolator within sight + supplementary bonding to all metalwork + SELV chromotherapy lighting; BS 7671 Section 702 compliance; £450–£1,200 install. Garden lighting design: layered (path + feature + ambient + accent) — Cullen Lighting outdoor + Hunza + Lumena ranges premium spec.
