# Electric Power Supply To Workshop



## custard (4 Mar 2019)

About seven or eight years ago I had my current workshop built, it's about 80 square metres and sits about 12 metres from my house. There's a 16 amp electric supply from my house to the workshop via a buried cable. However, I've just noticed that the cable, which runs under a flower bed adjacent to a dividing between ours and the neighbour's property, has started to rise up out of the soil. 

Anyone know what the regulations state and anyone any thoughts on how I could go about remedying this?

Thanks


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## shed9 (4 Mar 2019)

custard":1q7jeh97 said:


> About seven or eight years ago I had my current workshop built, it's about 80 square metres and sits about 12 metres from my house. There's a 16 amp electric supply from my house to the workshop via a buried cable. However, I've just noticed that the cable, which runs under a flower bed adjacent to a dividing between ours and the neighbour's property, has started to rise up out of the soil.
> 
> Anyone know what the regulations state and anyone any thoughts on how I could go about remedying this?
> 
> Thanks



BS 7671-2008 regs, regulation 522.8.10 is the reference here. 

'Buried cables, conduits, and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground'

This is 17th edition, not seen the 18th version yet which came out last year, can't imagine there is a huge change here but maybe someone else can confirm this.

18" is the norm for burying SWA.

Why is it rising up?


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## SammyQ (4 Mar 2019)

Some feckin worms or moles you got on the South Coast Custard...or, do you have a prison next door?? :shock: 

Sam :-"


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## screwpainting (4 Mar 2019)

I suppose it depends on how deep it was installed in the first place?.
I had a similar problem with a supply that had been laid to a Gazebo for the lights,pond and additional sockets so nothing serious. It was up against the fence and the ground was full of shrub and tree roots, a right mess. What I did, was to chop down (with a brick hammer) a small trench, then I laid a couple of old concrete fence posts over the cable with the cable in and under, the old fence rebate, then I buried the lot, about six inches deep I think. 
I've no idea how it ended up above ground though, haven't seen it since, which is good


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## Trevanion (4 Mar 2019)

It's the exact same thing with large stones, seems like no matter how many hundreds of years a field has been ploughed, you'll find a whomping big stone in the middle of the field each time you do it. I'm certain they just rise out of the ground over time.


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## custard (4 Mar 2019)

shed9":lnojpxpa said:


> 18" is the norm for burying SWA.



Thanks for that. But what is SWA?


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## custard (4 Mar 2019)

screwpainting":1ng7v7si said:


> I laid a couple of old concrete fence posts over the cable



Yes, similar things have been going through my mind, but I wondered if there was something that builders traditionally use for this, something that doesn't naturally rise out of the ground.


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## custard (4 Mar 2019)

Trevanion":162274qf said:


> I'm certain they just rise out of the ground over time.



I recall it's something to do with the soil below a stone freezing first and progressively pushing the stone up. But I can't remember the explanation for why the soil should freeze first underneath a stone!


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## shed9 (4 Mar 2019)

custard":m0lhd5dl said:


> shed9":m0lhd5dl said:
> 
> 
> > 18" is the norm for burying SWA.
> ...



Sorry, SWA = Steel Wired Armoured cable.


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## Sheffield Tony (4 Mar 2019)

SWA=Steel Wire Armoured

As well as depth of burial to avoid damage, it is usual to bury it in a layer of different material e.g. sand, under a warning tape.


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## Aquachiefofficer (4 Mar 2019)

It's easy to check if you've got SWA cable without peeling off the outer covering.
Take the front off your distribution board and look at the end where the outer layers have been cut away to separate the individual conductors to connect to the buses. Check that the wire armouring has been exposed for about 2 cm and an earth clamp has been fitted to this with a suitable length of earth wire to the earth bus. I laid one of these to the wife's gin palace last summer.
Stones rise to the surface because the smaller particles of soil can drop below them during any movement. You can demonstrate this by putting a handful of pebbles in a container and covering with sand. Shake the container for a few seconds and you will find the pebbles rising to the surface.
Regards, Paul (hammer)


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## basssound (5 Mar 2019)

I bury my armoured cable at least two spades deep, reason is most work down in the ground around the house is up to a spade depths deep, twice as deep is extra safe.


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## [email protected] (5 Mar 2019)

Buried things can often rise to the top through normal activity and movement in the soil, even earthworms will affect that, 18 " to 1 metre depth should be used, and used a good heavy armoured cable ordinary cable can be chewed through depending on the wild life situation in your area. then fit a fuse box into the workshop for safety. By the way not all blue 16 amp/ plug sockets are waterproof.


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## Woody2Shoes (5 Mar 2019)

A quicker way to tell if it's SWA is to use a magnet!

Although it's technically correct that it should be 450mm deep with a warning tape above, I wonder if - in this case - the situation is complicated by - as you describe it - the fact that the cable runs alongside your boundary with next door. I wonder if there's a possibility that someone in the future may try and put in a new fence post/trellis and get a surprise - I guess fairly remote. In an ideal world it might perhaps have been routed differently.

I wouldn't bother to do anything with it, if it were mine - other than perhaps to double-check that it is SWA and is properly protected by at least overcurrent protection (MCB). My incoming supply cable (SWA) is visible for a couple of feet by the house, before it goes underground.

It seems unlikely that frost heave would move a cable like this very far - I'm guessing you don't get very much hard frost near the south coast anyway.

Cheers, W2S


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## SammyQ (5 Mar 2019)

> Buried things can often rise to the top through normal activity and movement in the soil, even earthworms will affect that



Not wishing to cause offence, but...if the above the case, how come roman remains are always so deeply buried on Time Team? I know that is a superficial, perhaps even incorrect question, but my understanding was that soil fauna activities rotated soil _upwards_ i.e. surface deposition, gradually burying things laid on, or near, the surface?

Sam, willing to be educated.


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## Woody2Shoes (5 Mar 2019)

SammyQ":2d310csu said:


> > Buried things can often rise to the top through normal activity and movement in the soil, even earthworms will affect that
> 
> 
> 
> ...



Interesting topic. I live in an area of heavy weald clay, with increasingly infrequent and mild frosts. IME things sink, never to be seen again, as if they were dropped in a pond. I think that whether things move upwards or downwards or stay put is driven by climate (frost heave is a real problem in places like Canada) and by local geology (I'm sure sandy soil could work differently from clay soil).

Cheers, W2S

PS also vibration from e.g. traffic can definitely provide the energy to move soil up/down.


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## screwpainting (5 Mar 2019)

Isn't this one of those situations where a thorough understanding of 'Sod's' law (get it) is essential (homer)


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## Woody2Shoes (5 Mar 2019)

Of course, one of the reasons the regs say to bury cable 450 deep is to get below the area of topsoil affected by frost and earthworms etc. - you'd expect to be below the topsoil layer. It's impossible to know if the cable was originally installed per the regs anyway (quite conceivably not).


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