Wiring a socket to under-stairs shed.

[yorkieUK]

My CU is at the top of my stairs. There is conduit running straight down the corner of the wall from the CU, to the outside shed which is directly under the stairs. The wiring that runs through it, is for the light (and light-switch) that is already installed in the shed.
I'm wanting to install a double socket in the shed, so routing the cable from the shed to the CU is easy due to the existing conduit, but I'm not sure how to wire it in to one of these new CU's.
Please can someone tell me what cable rating I need, and how to wire it to one of the redundant breakers in the CU.
Thanks.

 

[ultomoat]

and how to wire it to one of the redundant breakers in the CU.
Thanks.

That would be the act of creating a new circuit - which requires sign off from your local authority Building Control dept under Part P regulations. It's possible to have them come and certify your work, though probably easier and cheaper to call in a professional electrician and have them do all of the paperwork for you.

Why is there a shed under your stairs?

 

[securespark]

Some houses have a store room under the stairs but it is only accessible via a door on the external wall.

 

[winston1]

The cable required is 2.5mm twin and earth. To get round the "new circuit" and associated hassle and expense connect it as a spur on one of your existing socket circuits.

 

[Taylortwocities]

Indeed, you can even "spur" it from a ring final MCB in your consumer unit (CU).

By the way, does your CU have RCD protection. Your new socket must be RCD protected.

 

[ban-all-sheds]

The guy doesn't know what to do with L/N/E conductors inside a CU - not sure you should be advising him to do that.