Circuit to garage, possible to replace junction box in house with single socket?

29 Jan 2023
Reaction score
United Kingdom
So, 12 year old house with dedicated circuit from CU to garage. This runs twin and earth to a junction box by back door, at this point the wire changes to 4mm, to the garage. The garage has a further mini CU with a lighting circuit and a circuit powering electric garage door and several sockets.

Where the junction box in the house is situated is exactly where I’d like to add a socket to plug a table lamp in. A single socket would be physically easy to fit where the junction box is now, no mess or chasing out a spur from another socket and damaging wallpaper.

So, would it be feasible from an electrical perspective to use a single socket as an easy way to give me the socket I need, where I need it, and act as a pass-through to the garage?

If not, could I perhaps replace the junction box with a 13AMP FCU, and spur a socket directly above the junction box?

Thank you in advance, and if it’s not feasible (too much load going through the socket etc., no problem, I just won’t do it.
Sponsored Links
What size cable runs from house CU to the junction box ,and what amperage is the breaker ( MCB ,RCBO ? ) that protects the circuit ?
Hi, the cable to the junction box is 2.5, the breaker is B20
Is the circuit protected by an RCD ?
What breakers ,amperages, protect the circuits in the garage CU ?
Sponsored Links
OK, so the house CU has a 63A 30mA RCCB, then a B20 MCB for the garage circuit. Then 2.5mm to the junction box, then 4mm from junction box to the garage main switch (Eaton Memera 2000) with 100A rating.
And yep, I’ll be adding a grommet where the wire exits back of the junction box pattress!


  • EEE88075-5938-4E00-89E1-71F66993468D.png
    1.1 MB · Views: 41
  • 0DD07A88-7C01-4B2B-99DB-80A6B9BB2254.png
    1.6 MB · Views: 43
  • 5588C02E-0BD9-4B83-AB1E-E0D1E369ED99.jpeg
    693.5 KB · Views: 40
Please show us a clear picture of the terminals and wiring connections on the back of whatever it is that you are calling a junction box.
Together with a full pic of your house consumer unit showing all breakers.
Is there a fused connection unit for the lighting circuit in your garage ?
Here you go. No other protection/FCU in garage other than the Eaton main switch. Thank you.


  • E7019664-3DDF-4E3E-A517-1E622D7F6D70.jpeg
    655.6 KB · Views: 39
  • 7FFD4A5B-CCA8-4659-974D-AE7693D6900F.jpeg
    142.7 KB · Views: 45
  • 5A49A560-6327-4FC2-8411-CF733ED2E7D6.jpeg
    972.7 KB · Views: 36
That 'junction box' is actually a flex outlet plate. It can be replaced with a single socket.
You don't need FCUs or anything else.

The RCD in the consumer unit is a type AC which is not suitable for socket outlets, it should be changed to a Type A, however there is no direct replacement for the one that's in there.
Other options include moving that circuit to a Type A RCBO, but that involves a certain amount of rearrangement in the consumer unit.

How is the armoured cable terminated outside or at the garage?
Thank you flameport, so while it sounds like I could replace the flex outlet plate with a socket and call it job done, would it be remiss or out of the question to do so without changing the RCD type? Worrying, as that RCD type is being used throughout the house including for sockets.
The armoured cable is terminated direct to the mainswitch in the garage

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links