Power cable to shed

i am wanting to lay some armoured cable down my garden to two sheds and some decking. What size cable should I use and how deep does it need burying?

Obviously I will get an electrician to do all of the technical bits when needed

Thanks for and help/advice

 

It all depends on what load you will need and how far it is. Why don't you ask the electrician that you are going to use? Don't forget this is notifiable work so you or your electrician will need to involve building control before you start.

 

Sizing the cable and knowing how deep to bury it are technical bits, so obviously you will now get an electrician.

 

Yes boss

Here’s me thinking the connecty uppy to the big bad box in the garage with the exciting flicky switch bits was the technical stuff

 

That is about 50% of the tekky stuff.

 

but if BigTree does all the digging of the trench (to the depth his electrician specifies) it will save him a lot of £s

 

It is, but there is also the legal bit.

If you want someone to sign the bits of paper, ask them where they want the cable run etc.

 

I agree and in my post above I assumed the electrician would specify the route as well as the depth.

 

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2018, except for the departures, if any, detailed as follows:​

 

You thought wrong, and here's me thinking that you were never getting an electrician in the first place.

 

The cable size is determined by the cable length and the total load.

Specifying is quite technical because for various reasons voltage drop in the cable must be within certain limits.
The cable must be able to cope safely with the maximum load as restricted by the mcb.

But the electrician also needs to choose the correct earthing requirement as that will influence the cable spec too.

And rcd protection needs consideration.

Whilst you wait to hear back from your electrician, this calculator will give you an indication:

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

And the type of cable, and the method of installation etc etc, which you know, but our OP doesn't.

 

The general guidance would be bury it deeper than anyone would be digging, and put marker tape (cables below, danger) and a layer of sand above the cable.
If the cable is below a patio you may not need to go as deep as in a vegetable patch.
Also bury it somewhere unlikely to be disturbed eg the edge of the plot, and leave a diagram of the route with the rest of the documentation.
Regarding the size, the electrician will decide after doing some calculations and measurements. Could be anything from 1mm 2 core for a few lights near the house, to 16mm 3 core for a growing operation at the bottom of the garden.

 

Across my yard, two ducts to the outbuildings, one for SWA to be pulled through and one for ELV cables.

 

And if you were to use 6mm swa should be ok for average needs