SWA across concrete footpath

[KiloBravo]

Hi,

So im hoping for some advice on running swa to my garden room from my house CU.

Its going to be clipped to the fence the majority of the way down to the garden room but to get to that point, it needs to come out the sidewall of my house (where the CU is) and across a narow concrete pathway to the fence, before it can be clipped. It also doesn't help that the cable will come out of my house wall above a gully.

Whats the most common method to achieve this? Is it just drilling out a channel in the footpath deep enough to get the cable in and then fill? Also, its 16mm 3 core swa, so it doesn't bend easily!

Pic attached (blue box is roughly where the CU is).

Would love some pointers, assume this must be a common scenario ‍...

 

[flameport]

If under the path it will need to be deep enough so that the cable is below the concrete slab, and therefore not affected by any movement or cracking of the concrete.
Cutting into concrete across a narrow strip like that between a building and a fence will be a pile of bother.

Clipped to a fence is also dubious.
Please add photos of the rest of the route, it's very likely there is a better option.

16mm² is likely grossly oversized. Whole houses are supplied with less.

 

[KiloBravo]

Not sure if you saw the pic attached but the concrete alleyway/side access is not concrete slabs per se, but just solid concrete all the way through. This also wraps round the whole side of the house and the rear to form the patio. No matter which way I go, there is the same concrete to contend with

If not cutting across the path, what other options are there?

Ill get another pic of the garden when I get a chance but I was advised it should be fine clipping it by a (retired) sparky as its out of harms way, behind shrubs etc. He also mentioned clipping to the gravel board beneath the fence as its stronger but that it might be a painful task.

Its 16mm because its a 52m run and the garden room will have a 2.5kw AC unit, 12 double sockets with office equipment attached and the odd power tool plugged in. I also wanted to future proof it a little. I was going to go 10mm but I think the drop off meant it was better to go 16... does it still sound like overkill?

Edit: attached a couple of pics but theyre not the clearest. The fence is currently obscured by all the mess I have lying around

 

[plugwash]

Doing anything to a concrete slab in such a confined space will be a massive PITA.

I'd think you would be better off either running internally or clipping to the outside wall of the house until you get to the back of the house and have more room to work. Then go underground.

Your picture doesn't show around the back of the house, but if there is a narrow strip of concrete next to the house, I'd try and dig under it from the rear. Then drill through it to pass the cable down.

 

[KiloBravo]

Doing anything to a concrete slab in such a confined space will be a massive PITA.

I'd think you would be better off either running internally or clipping to the outside wall of the house until you get to the back of the house and have more room to work. Then go underground.

Your picture doesn't show around the back of the house, but if there is a narrow strip of concrete next to the house, I'd try and dig under it from the rear. Then drill through it to pass the cable down.

I attached a couple more pics on my subsequent post which might help a little, but they dont show the back of the house. Ill take another pic in the morning that shows it a bit clearer.

Purely out of curiosity, what makes it difficult to drill a channel in a confined space? Is it not being able to get a good angle ?

EDIT: Just found a video of someone doing what it was i had in my head...albeit, looks like he has a bit more space than I do...its at the 2 minute mark.

 

[ericmark]

Could leave it on top, what I did was lay paving bricks with some sand under them, mainly to stop pools of water, but also hides the cable.

Today I have an angle grinder so could cut a channel and fill it with sand, but my SDS does not have a rota stop, so not ideal.

 

[JohnW2]

Doing anything to a concrete slab in such a confined space will be a massive PITA. .... I'd think you would be better off either running internally or clipping to the outside wall of the house until you get to the back of the house and have more room to work. Then go underground. ...

I would be inclined to agree with all that.

Your picture doesn't show around the back of the house, but if there is a narrow strip of concrete next to the house, I'd try and dig under it from the rear. Then drill through it to pass the cable down.

That would presumably make sense (IF your premise were correct), but it sounds as if there is a lot more than 'a narrow strip' of concrete at the back ....

..... solid concrete all the way through. This also wraps round the whole side of the house and the rear to form the patio.

Given all that, maybe 'on the surface' (per eric), or even 'overhead', might be worth considering?

 

[Murdochcat]

Why 16mm FFS ? Are you planning on building another house

 

[mattylad]

The op may mean that 16mm is the OD of the cable, not the csa of the cores.

 

[Murdochcat]

The op may mean that 16mm is the OD of the cable, not the csa of the cores.

Thats not how I read post # 1

 

[KiloBravo]

Could leave it on top, View attachment 414585 what I did was lay paving bricks with some sand under them, mainly to stop pools of water, but also hides the cable.

Today I have an angle grinder so could cut a channel and fill it with sand, but my SDS does not have a rota stop, so not ideal.

Hadn't seen these before. I'll certainly keep that as my backup option, or even temporary one until I find a solution. Thanks

 

[KiloBravo]

Given all that, maybe 'on the surface' (per eric), or even 'overhead', might be worth considering?

Someone had mentioned overhead to me before, via catenary wire. But I'm not sure how that would work without building a pillar for that particular purpose on the fence side of that path?

 

[KiloBravo]

Why 16mm FFS ? Are you planning on building another house

Answer is in my second post (post #3). I confirmed the requirement with a sparky and also used a calculator online , both said 16mm would be safer with that length of run due to drop-off.

The op may mean that 16mm is the OD of the cable, not the csa of the cores.

Thats not how I read post # 1

Definitely 16mm, the cable diameter itself is around 21mm.

 

[JohnW2]

Someone had mentioned overhead to me before, via catenary wire. But I'm not sure how that would work without building a pillar for that particular purpose on the fence side of that path?

Yes, you'd obviously need some sort of post to attach the catenary wire to at the fence end of the overhead run. However, I imagine that with a bit of thought, it could probably be part of a 'garden feature', and hence not too bad aesthetically!

 

[jj4091]

If you can clip it to the wall under the render as far as the corner it will be a lot easier to then cut a channel acoss the concrete with an angle grinder to the fence and break it out with an SDS chisel. If you are going to fix it along the base of the fence then the exit won't need to be square and the angle grinder should give a nice curve to bring the cable up. But it should not be too difficult to bury it a reasonable depth behind the shrubs.