New SWA 3core cable 2.5mm2

[oldbiker]

Hello, free Electrical Advice please.
Before I call a sparkie to upgrade my consumer unit I thought I would bring my outside power up to date. I have a twin+earth 6.0m2 under my floor, running outside to my shed and into a 2 way consumer unit, lights and power.
As far as I can remember this was put under my patio in a length of steel tube and I don't think it was sealed either end.
Because of costs, is it alright to cut the 6.0m off inside my garage and then run SWA 3 core 2.5mm2 under my slabs and into my new workshop?
If so, could I use a metalclad box and blanking plate for the join?
Should the timber workshop consumer box be on a fireproof backing plate?
Would I need another earth inside the workshop?
Thanks for any help.

 

[DPG]

I agree with the OP, it sounds a good idea to do the whole run on one length of SWA. Good to hear you're getting an electrician in.

 

[Norah Nabino]

Thanks for all the info guys. I intend to get sparks to do all the connections, just thought I could save him time by running the cables myself. The existing to the shed is still working but needs to be brought upto date.
The load would be 3 or 4, 13 amp sockets and a strip light.
The existing was put in by a spark and the earth from the main consumer box is 6mm.
Distance from mains to workshop is about 20 metres. Just thought I could save some money by using existing inside the house and renew the outside stuff. Its expensive cable.
The new consumer unit will be an MK dual RCD with 10 MCBs.

Is the 2.5mm cable going to be swa or not??

 

[oldbiker]

"Also, it doesn't need to be armoured".....thanks spoon, you have saved me a bit of cash.
Sparks said its fine and he is going to extend the ring (2 double metalclad) and a strip light in the new build.