Outdoor electrical work is increasingly common — garden lighting, outdoor sockets, hot tubs, outbuilding supplies, and EV chargers. This guide covers BS 7671 Section 714, IP ratings, RCD protection, SWA cable installation, burial depths, and Part P requirements for every type of outdoor electrical installation.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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Outdoor electrical work presents unique challenges compared to internal installations. Equipment is exposed to rain, moisture, temperature extremes, UV radiation, physical damage, and in some cases, corrosive soil conditions. The combination of electricity and wet outdoor environments creates significant safety risks that BS 7671 addresses through specific requirements for outdoor installations.
The range of outdoor electrical work has expanded significantly in recent years. Traditional garden lighting and outdoor sockets have been joined by EV chargers, hot tubs, garden rooms and home offices in outbuildings, outdoor kitchens, security systems, and decorative landscape lighting. Each has its own requirements and considerations.
For electricians, outdoor work is a growing revenue stream. Homeowners increasingly want to extend their living space outdoors, and every outdoor electrical installation requires professional design, installation, testing, and certification. Understanding the specific regulations for outdoor installations — particularly cable selection, IP ratings, and the Part P notification requirements — is essential.
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BS 7671 Section 714 covers "Outdoor Lighting Installations" but its requirements apply broadly to all outdoor electrical installations. The section supplements the general requirements of BS 7671 with specific provisions for equipment and cabling exposed to outdoor conditions.
Key requirements of Section 714 include:
In addition to Section 714, other Part 7 sections may apply depending on the specific installation: Section 702 for swimming pools and paddling pools, Section 708 for caravans and caravan parks, and Section 722 for EV charging equipment.
The Ingress Protection (IP) rating determines how well electrical equipment is protected against the ingress of solid particles and water. For outdoor installations, the water protection rating (the second digit) is critical.
Protected against objects over 1mm and splashing water
Dust-protected and protected against water jets
Dust-tight and protected against water jets
Dust-tight and protected against powerful water jets
Dust-tight and protected against immersion
For most outdoor installations, IP65 is the recommended minimum. IP44 is acceptable for equipment installed under a covered porch, carport, or overhang where direct rain exposure is limited. For equipment at ground level, in locations exposed to heavy rain, or subject to washing down, IP66 is preferred. For in-ground installations (such as ground-level uplighters), IP67 or IP68 is required.
When selecting outdoor equipment, always check that the IP rating is for the complete installed unit — not just the enclosure. Cable entry points, gaskets, and covers must all maintain the rated IP level when the unit is correctly installed.
All outdoor electrical circuits must be protected by a 30mA RCD. This requirement comes from multiple regulations:
The RCD should be located inside the building, in the consumer unit or a distribution board, so that it is accessible and protected from the weather. Individual RCBOs provide the best discrimination — a fault on the outdoor circuit trips only that circuit, not other circuits in the property. Where a group RCD is used, the outdoor circuit should not share the RCD with critical indoor circuits (such as the freezer or alarm system) to avoid nuisance tripping causing inconvenience indoors.
For outdoor circuits in wet conditions, consider using a time-delayed RCD (Type S) upstream of the 30mA RCD to provide discrimination. This prevents a fault on the outdoor circuit from tripping the upstream RCD and disconnecting other circuits.
The cable type for outdoor installations depends on the installation method — underground, surface-mounted on external walls, or overhead. The two most common cable types for domestic outdoor circuits are Steel Wire Armoured (SWA) cable and Hi-Tuf (PVC-sheathed armoured) cable.
SWA is the standard cable for underground outdoor circuits. It consists of copper or aluminium conductors, XLPE or PVC insulation, a layer of steel wire armour providing mechanical protection, and an outer PVC sheath. The steel armour also serves as the circuit protective conductor (CPC) in many installations — though a separate CPC is recommended for domestic circuits.
Uses: Underground runs to outbuildings, garden lighting, outdoor sockets, hot tubs, EV chargers. Available in 2-core, 3-core, 4-core, and 5-core configurations. Common sizes for domestic work are 2.5mm², 4mm², 6mm², and 10mm².
Hi-Tuf (or PVC/SWA/PVC) is a lighter-duty armoured cable suitable for surface-mounted outdoor installations and some buried applications. It has a similar construction to SWA but with a thinner PVC outer sheath. It is easier to handle and terminate than full SWA cable.
Uses: Surface-mounted runs on external walls, short underground runs to garden features. Not suitable for long underground runs or locations subject to significant mechanical damage. Properly rated for outdoor UV exposure.
Standard PVC twin-and-earth cable (6242Y) is not suitable for outdoor use — it is not UV-resistant, has no mechanical protection, and is not rated for direct burial. If twin-and-earth must be run externally (for example, a short run from a wall-mounted switch to an external light), it must be enclosed in UV-resistant conduit or trunking.
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The burial depth for underground cables is specified to protect them from accidental damage during future excavation work (gardening, landscaping, utility trenching). BS 7671 and the IET Guidance Note 1 provide the following guidance:
SWA cable in standard garden soil
Areas subject to vehicle traffic
Areas subject to ploughing
In addition to the burial depth, the following protection measures are required:
The cable route should be documented and ideally recorded on a plan of the property. This helps future contractors and homeowners avoid the cable during excavation work.
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Start free trialGarden lighting installations range from simple mains-powered wall lights and bollard lights to complex landscape lighting schemes with multiple circuits and control systems. The electrical requirements depend on whether the system is mains voltage (230V) or extra-low voltage (typically 12V or 24V).
Mains-voltage garden lighting uses standard 230V luminaires rated for outdoor use (minimum IP44, recommended IP65). The circuit requires 30mA RCD protection, and the wiring must use outdoor-rated cable (SWA for underground runs). Luminaires must be UV-resistant, corrosion-resistant, and suitable for the installation environment.
Advantages: Brighter output, longer cable runs without voltage drop issues, wider range of luminaire styles. Disadvantages: Higher safety risk, requires professional installation, more expensive cabling (SWA).
ELV garden lighting uses a mains-powered transformer (located indoors or in a weatherproof enclosure outdoors) to supply 12V or 24V to the garden luminaires. The low voltage significantly reduces the electric shock risk, making ELV lighting suitable for areas where people may come into contact with fittings.
Advantages: Safer (reduced shock risk), easier cable installation (low-voltage cable does not need SWA), suitable for water features and in-ground use. Disadvantages: Lower output per fitting, voltage drop on long cable runs limits the number of fittings per transformer, transformer adds cost and requires an indoor mains supply.
Regardless of the voltage, the mains supply to the transformer or the mains-voltage lighting circuit requires 30mA RCD protection and appropriate cable sizing. For SWA cable runs to garden lighting positions, the cable sizing calculator should be used to verify that the cable size is adequate for the load and the cable run length.
Outdoor socket outlets are one of the most requested domestic electrical additions. They provide a convenient power supply for garden tools, outdoor entertainment equipment, Christmas lighting, and general outdoor use. The installation requirements are straightforward but must be followed carefully.
A single outdoor socket can be added from an existing circuit (as a spur) or installed on a new dedicated circuit. If adding a spur, ensure the existing circuit has adequate spare capacity and that the spur is taken from a suitable point. A new dedicated circuit provides better protection and avoids overloading existing circuits.
Hot tubs and swimming pools present some of the highest-risk outdoor electrical installations due to the combination of electricity and full-body water immersion. BS 7671 Section 702 covers swimming pools and similar installations, while hot tubs are covered under a combination of Section 702 and Section 714.
A hot tub typically draws 13A to 32A depending on the model (2.2 kW to 7 kW). The circuit must be on a dedicated supply from the consumer unit with 30mA RCD protection. The cable must be SWA for the outdoor run, correctly buried with cable covers. An isolator switch must be provided within sight of the hot tub but not within reach of a person using the tub — typically 2-3 metres from the tub. Supplementary bonding of all extraneous conductive parts within 2 metres of the tub is required.
Swimming pools have zone requirements similar to bathroom installations but more stringent. Zone 0 (the pool basin), Zone 1 (up to 2m horizontally from the pool edge and up to 2.5m above the floor), and Zone 2 (1.5m beyond Zone 1) each have specific requirements for IP ratings and permitted equipment. Only SELV at 12V is permitted in Zones 0 and 1.
Both hot tub and swimming pool installations are notifiable under Part P. A full Electrical Installation Certificate (EIC) is required — not a Minor Works Certificate — because the installation typically involves a new circuit.
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Try it free for 7 daysEV chargers are increasingly common outdoor installations. While the general requirements are covered in the dedicated EV charger installation guide, there are specific outdoor considerations:
For EV chargers mounted on freestanding posts or on detached garages, the SWA cable run and earth rod installation represent significant additional work compared to a simple wall-mounted installation on the house. The voltage drop calculation is critical for longer cable runs — a 32A EV charger on a long SWA cable run can easily exceed the 5% voltage drop limit.
Most outdoor electrical work is notifiable under Part P of the Building Regulations. The following outdoor installations are notifiable:
The work must be either self-certified by an electrician registered with a Competent Person Scheme or notified to the local authority building control department. A full EIC is required for new circuits; a Minor Works Certificate may be used for simpler additions (such as adding an outdoor socket as a spur from an existing circuit, where no new circuit is being created).
Elec-Mate's AI Installation Specialist provides guidance on outdoor wiring — cable selection, burial depths, IP ratings, RCD requirements…
Try it free for 7 daysA step-by-step process for installing a typical outdoor electrical circuit (garden socket, outbuilding supply, or garden lighting) using SWA cable.
Assess the outdoor installation — equipment to be supplied, cable route from the consumer unit to the outdoor position, burial depth requirements, and any obstacles (driveways, paths, tree roots, existing services). Design the circuit: calculate the load, select the cable size (accounting for derating factors for buried SWA), verify voltage drop, and select the protective device. Check Part P notification requirements.
Install the appropriate protective device in the consumer unit — typically a 30mA RCBO sized for the outdoor circuit. If the consumer unit does not have a spare way, consider whether a small outdoor distribution board or a consumer unit upgrade is required. Ensure adequate supply capacity for the additional outdoor load.
Dig the cable trench to the required depth — minimum 500mm in garden areas, 600mm under driveways and paths. Check for existing underground services (gas, water, drainage, telecoms) before digging. Use a CAT scanner and plans where available. Lay a bed of fine sand (approximately 50mm) in the bottom of the trench.
Lay the SWA cable in the trench on the sand bed. Do not pull the cable tight around corners — use gentle curves with a minimum bend radius appropriate for the cable size. Place cable covers (tiles) directly over the cable. Backfill with fine sand to approximately 150mm above the cable, then lay route marker tape. Complete the backfill with excavated soil.
Terminate the SWA cable at both ends using appropriate SWA glands. At the consumer unit end, strip back the outer sheath, armour, and inner sheath, fit the SWA gland, and connect to the protective device. At the outdoor end, fit the SWA gland to the weatherproof enclosure, socket, or junction box. Connect the equipment and verify correct terminations.
Carry out the full testing sequence before backfilling: continuity of protective conductors (including the SWA armour if used as CPC), insulation resistance, polarity, earth fault loop impedance, prospective fault current, and RCD operation. Complete the Electrical Installation Certificate. Backfill the trench and reinstate the surface. Issue the certificate and Part P notification.
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