Can I add an extra socket myself?

This is the job that sits exactly on the line, and the honest answer has two halves. In England and Wales, adding a socket to an existing circuit in an ordinary room was removed from the notifiable list in 2013, so no building control notification is required. But the wiring regulations still apply in full, and the failure modes here are silent.

Safety

Step by step

1. Understand what "not notifiable" actually means.It means you do not have to tell building control. It does not mean the work is exempt from BS 7671, and it does not mean an unsafe result is acceptable. You are still required to leave the installation safe.
2. Establish whether the circuit is a ring or a radial.This is the crux. A ring final circuit has two cables at most sockets and returns to the same MCB. A radial has one cable feeding onward. You cannot reliably tell by counting cables at one socket, because a spur also has one — this needs continuity testing at the board.
3. Understand the spur rule.You may take one unfused spur from a socket on a ring, feeding one single or one double socket. You may not spur from a spur, and you may not take a second spur from a socket that already has one. This is the rule most commonly broken, and the result overloads a single 2.5mm cable that then sits inside a wall.
4. Know where you may not do this at all.Inside a bathroom or shower room, or outdoors, adding a socket is notifiable work and must be certified. There is also almost nowhere in a domestic bathroom where a socket is permitted at all, other than a shaver supply unit outside the zones.
5. Consider a fused connection unit instead.If the only aim is a permanent appliance, a fused spur taken correctly from the ring is often the tidier answer, and it limits the spur to 13A by design.
6. Consider the physical work honestly.Chasing a wall, fitting a back box in masonry or a dry-lining box in plasterboard, running cable in permitted zones, making good and decorating are all significant work in themselves and are the bulk of the time.
7. Decide, and be honest about competence.If you cannot test the ring's continuity, verify polarity, measure earth fault loop impedance and confirm RCD operation afterwards, you cannot verify your own work — and unverified socket work is the sort that fails an EICR years later at the worst moment. That is the real reason to pay an electrician.
8. Ask the electrician for the right paperwork.For an addition to an existing circuit, ask for a Minor Electrical Installation Works Certificate. Keep it with the house papers — it is what a buyer's surveyor or a future EICR will want to see.

Tips

• If the goal is just more outlets in one place, replacing a single socket with a double in the same back box is a far smaller job than adding a new position. Deep back boxes matter here.
• Say what the socket is for when you get a quote. A socket for a TV wall is different from a socket for a workshop bench, and an electrician may recommend a dedicated circuit for the second.
• Get any socket additions done at the same time as other work. The making-good is what costs, not the accessory.

Common mistakes

• Spurring from a socket that is already a spur — It puts two sockets' worth of load on one 2.5mm cable protected at 32A. Nothing looks wrong and nothing trips; the cable simply runs hot in the wall under sustained load.
• Assuming two cables at a socket means it is on the ring — Two cables can also mean a socket mid-way along a radial, or a socket feeding a spur onward. Only continuity testing at the board tells you the topology.
• Running cable outside the permitted safe zones — Cables run diagonally or across the middle of a wall are exactly where someone drills later. Safe zones exist so that the next person can predict where cables are.

If it doesn't work

Questions people ask