Weatherproof Sockets: Outdoor IP66 and IP44 Sockets Explained

Plug an electric lawnmower into a kitchen socket, trail the lead out through the patio door, and you've created exactly the hazard the wiring regulations were written to prevent: a live cable lying across damp ground with no protection from a wet-weather earth fault. The fix is a single socket on the outside wall, fitted at first-fix while the walls are open. Add it after the plaster's on and you're chasing channels into finished render and paying an electrician for half a day's making-good. Get it specced before the sparky first fixes and it's twenty minutes of his time.

What it is and what it's for

A weatherproof socket is an ordinary 13A socket outlet built into a sealed enclosure with spring-loaded flaps that snap shut over the pin holes when nothing's plugged in. The seal keeps water and dust out of the live parts. That's the whole idea. A standard indoor socket has open apertures and a thin plastic faceplate that offers no protection against rain, hose spray, or condensation, so it can't legally or safely go anywhere it might get wet.

Outdoor sockets are governed by BS 7671, the UK wiring regulations (often called the IET Wiring Regulations or "the 18th Edition"). The regs don't just cover the socket itself. They dictate how the circuit feeding it must be protected, where the cable can run, and how deep it must be buried if it goes underground. Skip those rules and your electrician can't issue the certificate that building control and your own insurer will eventually want to see.

The two specs that matter are the IP rating (how well the enclosure keeps water and dust out) and RCD protection (a safety device that cuts the power in milliseconds if current starts leaking to earth, which is what happens when water gets into something live). Get both right and the socket is as safe as any inside the house. Get either wrong and it's a genuine electrocution risk.

IP ratings, sizes, and what the numbers mean

The "IP" in IP44 or IP66 stands for Ingress Protection. It's a two-digit code: the first digit is protection against solid objects and dust, the second is protection against water. Higher numbers mean better sealing. For outdoor sockets, only three ratings come up.

For a socket on the outside wall of an extension, where rain lands straight on it and you might one day point a pressure washer in its direction, fit IP66. It's the standard for exposed positions and the price difference over IP44 is small. Reserve IP44 for genuinely sheltered spots: under a deep porch, inside a carport, tucked up under the soffit (the horizontal board under the roof overhang) for festoon lights. If in doubt, go higher. There's no penalty for over-rating an outdoor socket, only for under-rating one.

Most weatherproof sockets come as single (one outlet) or double (two outlets). For an extension's outside wall, fit a double. The cost difference is a couple of pounds and a single socket is the thing people regret first, the day they want to run a lawnmower and a radio at once. The enclosure dimensions are larger than an indoor socket: a typical double IP66 unit is roughly 130mm wide by 180mm tall, deeper too, because the back box and gasket add bulk. Allow for that when you're deciding where it sits relative to door frames and downpipes.

There's a second type worth knowing about but not relevant to a wall: the pedestal socket, a free-standing weatherproof unit on a stake you push into a flower bed, fed by buried armoured cable. Useful for a socket out in the middle of a garden. For anything on the building itself, it's the surface-mounted wall socket every time.

How it gets wired and installed

This is the part homeowners get blindsided by, because the socket itself is the cheap, simple bit. The work is in the circuit and the cable route.

The socket is fed with 2.5mm² twin-and-earth cable ("2.5 T&E", the grey flat cable with two insulated cores and a bare earth). It either spurs off an existing RCD-protected ring circuit, or, better for anything that'll draw real load, runs as its own new circuit from a dedicated RCBO in the consumer unit (the fuse board). An RCBO combines the fuse and the RCD in one module, so the outdoor socket has its own protection and a fault outside won't trip the rest of the house.

Whatever feeds it, the circuit must be RCD-protected at 30mA. This is not optional. BS 7671 Regulation 411.3.3 makes 30mA RCD protection mandatory for socket outlets intended to supply equipment used outdoors. The 30mA figure is the leakage current at which the device trips, low enough to protect a person before a shock becomes lethal.

The cable route decides the rest of the job. Three scenarios cover almost every extension:

The cable runs through the cavity wall from inside. Where it passes through the outer leaf it must go through an approved wall sleeve or grommet that seals the hole and stops water tracking back inside. The electrician drills, sleeves, and makes good. Quick and tidy.

The cable runs exposed down the outside wall from a higher entry point. Surface cable on an external wall must sit inside UV-resistant conduit. Ordinary white plastic conduit goes brittle and yellow in sunlight within a couple of years; the grey UV-stable type is made for it. T&E cable should never run bare on an outside wall.

The cable runs underground to reach the socket, for instance to an outbuilding or a far corner. Buried cable must be steel wire armoured (SWA) cable, laid at a minimum depth of 450mm under open ground, with marker tape above it. You can't just trench in ordinary T&E, even in conduit. SWA has a steel sheath that protects against a spade strike and provides an earth path.

The socket should sit at a sensible height, usually 450mm or more above ground or paving, well clear of splash-back and standing water, and not directly beneath a gutter joint or downpipe outlet where it'll get a constant drip.

How much do you need and how much does it cost

For a typical extension you're fitting one or two outdoor sockets, not buying by the box, so quantity is simple. One double socket by the patio doors covers most needs: garden lighting, a mower, a pressure washer, a radio. Add a second under the soffit if you want permanent festoon or string lights without a trailing lead. An outbuilding or garage usually wants its own.

The socket unit itself is cheap.

That buys a branded IP66 double socket from any of the names below. The real cost is the installation: the cable, the RCD or RCBO protection, the wall penetration, the testing, and the electrician's time and certificate.

That installed range assumes an existing suitable circuit nearby to spur from at the low end, and a new dedicated circuit run back to the consumer unit (or a board upgrade) at the high end. A buried SWA run to an outbuilding pushes well past the top of that range because of the trenching, the armoured cable, and the extra terminations.

The single biggest saving is timing. Fit it at first fix, while the walls are open and the electrician is already pulling cable, and the marginal cost is tiny. Bolt it on after the plaster's dry and decoration's done and you're paying for channelling, making-good, and a return visit. Decide where your outdoor sockets go before the first-fix electrics start, not after.

External resource

IET Wiring Regulations (BS 7671)

The official IET page on BS 7671, the standard governing RCD protection and outdoor circuit requirements in UK homes.

electrical.theiet.org

Brands worth buying

You don't need an obscure brand. The mainstream UK accessory makers all do good weatherproof ranges, and any of them will be on the shelf at a wholesaler or the big merchants. BG (British General) and MK are the everyday workhorses, well-priced and stocked everywhere. Crabtree, Wylex, and Hager are common where the rest of the consumer unit and accessories match the same brand. Wandsworth sits at the premium end. For a homeowner the practical advice is simple: buy a double IP66 socket from BG or MK, hand it to your electrician, and spend your attention on the circuit, not the brand on the lid.

Alternatives

If you genuinely only ever need power in one fixed garden spot a long way from the wall, a pedestal socket on a stake, fed by buried SWA, can be neater than a long surface run. For temporary outdoor use, an RCD-protected extension lead rated for outdoor work is fine for an afternoon's hedge-trimming, but it's not a substitute for a fixed socket and should never be left out in the weather or run permanently. If you're after a charging point rather than general power, that's a dedicated EV charger circuit, a different beast with its own regulations, not an outdoor 13A socket.

Where you'll need this

• First fix electrics - the stage to run the cable and back box while the walls are open
• Electrical layout planning - decide outdoor socket positions here, before any cable is pulled
• Kitchen electrical provisions - outdoor sockets near patio and garden doors are planned alongside the kitchen circuits

Outdoor sockets come up on almost any extension or renovation that opens up an external wall, not just kitchen builds, so the decision to add one belongs in the first-fix electrical plan of whatever project you're running.

Common mistakes

The most expensive mistake is leaving it too late. An outdoor socket decided after first fix means cutting into finished walls and a return visit, several times the cost of getting it in early.

The most dangerous mistake is the rating. People buy an IP44 socket because it's a pound cheaper, fit it on a fully exposed wall, and the seal fails inside two winters. For anything rain hits directly, IP66 is the floor, not the upgrade.