Can I use an indoor extension lead outside?

Outdoors changes the consequences of a fault, not just the likelihood. Indoors, standing on a dry carpeted floor, a person is fairly well insulated from earth. On wet grass or a damp patio, that insulation is gone, and a fault that would give an indoor shock a bad but survivable outcome becomes far more dangerous. That is why outdoor equipment is specified differently.

Safety

Step by step

1. Check the RCD protection first, before anything else.Every outdoor supply must be 30mA RCD protected. If the socket you are plugging into is on an RCD or RCBO at the consumer unit, you have it. If you do not know, use a plug-in RCD adaptor — they cost very little and they are what stands between a cut cable and an electrocution.
2. Use a lead built for outdoor use.Outdoor leads and reels have sealed sockets with hinged covers, rubber or heavy PVC sheath, and an IP rating — IP44 is the usual minimum for garden use, meaning protected against splashing from any direction. An indoor lead has open sockets and thin flex.
3. Keep the socket end off the ground.The socket end is the vulnerable part. Hang it, stand it on something dry, or keep it under cover. A socket lying on wet grass will take in water regardless of its rating.
4. Unwind reels fully.Garden tools — mowers, hedge trimmers, pressure washers — are motor loads and often near the reel's limit. The coiled rating applies outdoors exactly as it does indoors.
5. Route the cable where you will not cut it.Behind you, over your shoulder for a hedge trimmer, and never in front of a mower. Cutting through the lead is the single most common garden electrical accident, and it is why the RCD is not optional.
6. Do not run a lead permanently through a window or door.A lead trapped in a closing window is being crushed, and a permanent arrangement is a fixed installation made of temporary equipment. If a shed or a greenhouse needs power all the time, it needs a proper supply installed by an electrician.
7. Bring it in when you have finished.Leads left out get sun-damaged, frost-damaged, chewed by animals and run over. A lead that has spent a winter outside should be inspected carefully before reuse and is often best replaced.
8. Inspect before every use.Run the flex through your hand looking for nicks, cuts and flattening. Check the plug and sockets for cracks and for water inside. Any damage to the outer sheath means the lead is finished — sheath is the weather protection.

Tips

• A plug-in RCD adaptor is the cheapest meaningful safety purchase most households can make, and it belongs with the garden tools, not in a drawer.
• Battery tools remove the problem entirely for mowing, trimming and blowing, and are now genuinely capable for domestic gardens.
• If you are using a pressure washer, remember it is directing water at exactly the connections you are relying on. Keep the socket end well away and under cover.

Common mistakes

• Using an indoor four-way on the patio because it is dry today — The sockets are open, dew and a passing shower are enough, and the failure is not gradual — a wet socket with a plug in it can fault immediately.
• Relying on the appliance's double insulation instead of an RCD — Double insulation protects against faults inside the tool. It does nothing about a lead you have just cut through with the tool.
• Leaving a lead running to a shed or greenhouse permanently — It is unprotected from weather and from damage, it is unsupported over its length, and it never gets inspected. A permanent need requires a permanent, certified supply.

If it doesn't work

Questions people ask