How to get SWA through exterior wall

[Donkmeister]

How does one usually pass SWA through an exterior wall? Below ground level, or above ground level? Or just at the most convenient level?

I want to run power to my shed, with the cable being buried underground. Google searches, DIYnot searches and looking in the Wiki, I haven't been able to find any information on the pretty universal task of running a cable through an exterior wall. Perhaps I'm being paranoid, but I don't want to end up with damp problems caused by a cable run!

The wall in question is a 1920s cavity wall, both skins are brick. The cable would be run approx 8 metres from my CU, through the ground floor ceiling void as my ground floor is concrete slab.

 

[oharaf]

If you run it through the ceiling void then carefully drill a hole through both skins. You will then need to creat a 'groove so that you can form the cable downward without over bending it.

To prevent water being carried along the cable into the property you will need to form a drip loop with the cable.

THIS WILL NOT BE THAT EASY WITH SPRINGY SWA!!!!!


but to suffice you can do it, using your saddles and clips to assist you!!!

You can then 'fill' the hole with mortar and /or silicone to seal it.

You will need to take into account any insulation in the ceiling void, do your calcs for current carrying and all that.

Are you sure there is no way you can exit throught the ground floor and use the wall of the property until you reach your trenching point??

 

[Donkmeister]

I think I could exit at/below ground level would certainly look better than trying to do a drip loop in chunky armoured cable. Presumably I drill the exit hole below ground level.

There's only two routes I can find:

1) Go all the way around the house, which is another 30 metres route
2) Route through ceiling void, chase cable drop down to below ground level on the inside of the external wall, but I'm not sure if my plaster is deep enough to hide a 6mm SWA.

Thanks for the reminder on calcs. I used my 17th edition and onsite guide to calculate the cable requirement... it's at home at the mo but I think with the distance and current it worked out to 6.0mm cores... so it's going to be thick.

This will of course be going on the spec for the BCO, I'm Part P-ing everything I do.

 

[rebuke]

If it's going straight down from where it comes out, then you don't need a drip loop - water isn't going to run up the cable...

Drip loops stop water coming in if a cable is coming vertically down to a hole (where it will obviously just follow the cable down, and straight into the hole if no loop present), or in some circumstances horizontally (as if the cable is even slightly off level then with enough water it might run in).

 

[ban-all-sheds]

my ground floor is concrete slab.

Won't that make it a tad difficult to take the cable out of the house underground?

 

[oharaf]

Sorry Rebuke, fell into talking sh1te mode!!! A week with 2 under 4 years, wife away on holiday and me trying to do the whole lot.

Going slowly insane, so thanks no drip loop.


I wouldn't relish the idea of trying to sink SWA into a wall and plaster.!!!!!!!!!!!!!

 

[Donkmeister]

my ground floor is concrete slab.

Won't that make it a tad difficult to take the cable out of the house underground?

I was imaging a session with an SDS chisel... is that a bad idea? The room will be completely emptied out so dust shouldn't be an issue, but I've never tried chiselling into a floor slab before (this one is over 80 years old).

Cheers for all the help guys, voltage drops and cable loadings I can deal with, it's this seemingly simple matter that's doing my head in!!!

 

[Donkmeister]

I wouldn't relish the idea of trying to sink SWA into a wall and plaster.!!!!!!!!!!!!!

The more I think about it, that part does seem like wishful thinking at best, sheer madness at worst... According to my neighbour, the plaster in these houses isn't even deep enough to hide a low-profile galvanised wall-box.

I think it might be significantly less hassle of I run it outside through the ceiling void, cleat it to the outside wall (with no drip loop ).

I like the "all cables hidden" look, but it's right next to a fence so won't be too visible.

Thanks again for all the help and suggestions

 

[bernardgreen]

This may not be acceptable under regs.

Fit a weather proof metal box on the outside of the wall. Terminate the SWA armouring in this box with the conductors only going through the wall inside a length of conduit glanded in back face of the box. Then junction the conductors to a suitable cable to complete the run to the consumer unit

 

[stargazer]

Or use twin & earth inside and SWA outside.