Cabling and a new patio

rajanm

We're planning on having a new resin patio built in the next couple of months. In the long term, we may build a garden office at the bottom of our garden. 

Does it make sense to lay some electric cables underground now to future proof it all?  What happens to the end of the cable?  Can it be safely secured? 

Also what are the options for extending WiFi from the house?  Is there any cabling we should lay for that?

We don't want a situation in a few years time where the only option is to dig into our patio!

nofoollikeold

Run two plastic conduits under the patio, one 25 mm, one 20mm.  Close off both ends but make sure you know where they are.  Then you could run a mains cable through one, and the network cable through the smaller one should you need to in future.  Also consider a second 25 mm in case of a need for more power, and even a third 25 mm in case you want to run water to the garden office.

rajanm

Mickey666 said:

Perhaps better than laying actual cables would be to install some ducting instead?  You can buy purpose-made ducting for such things in most builders merchants or, if the distance is not great, consider using a a length or two of standard plastic drainpipe.  You can then run power and data cables at a later date when actually required.

Ideally, data cables (for wifi extension) should not be laid in the same conduit as mains cable, but it almost certainly won't matter for a short distance.  For data cabling, smaller ducting should be fine - I've used standard 20mm plastic conduit because the various fittings and junction boxes are readily available and cheap as chips.  For power cabling, SWA cable should ideally be used and this is typically too thick for standard conduit, hence the drainpipe suggestion.  Also bear in mind that SWA cabling is not very flexible and certainly doesn't like right-angled bends!

But wouldn't you actually need to lay the cables in the ducting?  Otherwise, wouldn't you still have to dig the patio up to put the cables into the ducting that you've laid?  I'm probably missing something here !

EssexExile

Obviously you need to be able to get at both ends of the ducting!

williamgriffin

rajanm said:

Mickey666 said:

Perhaps better than laying actual cables would be to install some ducting instead?  You can buy purpose-made ducting for such things in most builders merchants or, if the distance is not great, consider using a a length or two of standard plastic drainpipe.  You can then run power and data cables at a later date when actually required.

Ideally, data cables (for wifi extension) should not be laid in the same conduit as mains cable, but it almost certainly won't matter for a short distance.  For data cabling, smaller ducting should be fine - I've used standard 20mm plastic conduit because the various fittings and junction boxes are readily available and cheap as chips.  For power cabling, SWA cable should ideally be used and this is typically too thick for standard conduit, hence the drainpipe suggestion.  Also bear in mind that SWA cabling is not very flexible and certainly doesn't like right-angled bends!

But wouldn't you actually need to lay the cables in the ducting?  Otherwise, wouldn't you still have to dig the patio up to put the cables into the ducting that you've laid?  I'm probably missing something here !

The trick is to leave each end exposed. 

grumbler

williamgriffin said:

rajanm said:

Mickey666 said:

Perhaps better than laying actual cables would be to install some ducting instead?  You can buy purpose-made ducting for such things in most builders merchants or, if the distance is not great, consider using a a length or two of standard plastic drainpipe.  You can then run power and data cables at a later date when actually required.

Ideally, data cables (for wifi extension) should not be laid in the same conduit as mains cable, but it almost certainly won't matter for a short distance.  For data cabling, smaller ducting should be fine - I've used standard 20mm plastic conduit because the various fittings and junction boxes are readily available and cheap as chips.  For power cabling, SWA cable should ideally be used and this is typically too thick for standard conduit, hence the drainpipe suggestion.  Also bear in mind that SWA cabling is not very flexible and certainly doesn't like right-angled bends!

But wouldn't you actually need to lay the cables in the ducting?  Otherwise, wouldn't you still have to dig the patio up to put the cables into the ducting that you've laid?  I'm probably missing something here !

The trick is to leave each end exposed. 

And even better to leave a rope/fishing-line inside

littleboo

^ This. Leave a bit of rope in the duct to pull through, secured at both ends.

Jeepers_Creepers

Use strong nylon line that won't rot if you don't get around to this for a few years. Also, as said above, SWA is pretty stiff cable, so don't expect it to get around bends.

Really, the only reason you wouldn't run the SWA right away is the purchase cost of it, but even that isn't a lot in the scheme of things. So if you are even half confident you'll want power down there in the future, then I'd go ahead and run it now - it can be laid directly in the soil if you wish. AfaIk, it'll only need to be 450mm (?) deep as it's going under a hard surface with little risk of being disturbed - you just lay warning tape above it. For CAT cables and other stuff, run a separate conduit tube with a pulling cord inside it.

For both, you need to consider how the cables will exit your house, the neatest way being to drill through your house wall below ground level and take it in under your floor - provided you can get a route to your CU this way.

How far away with the room be? In theory you could just fit an RCD-FSU spurred from your nearest socket, but that would limit your cable to 2.5mm2 which won't allow much future-proofing, and could well suffer a significant voltage drop if it's a significant distance; ie turning on a 2kW heater could make your lights flicker and potentially cause other issues. I would personally run a 4mm2 cable over even normal distances, and take this off a dedicated RCBO in your CU. (I thankfully went for this when we had a garage built 15 years ago, thinking I might want to run a welder at times. I have, but the real plus was when we had PV panels fitted a decade ago on the garage roof, and the cable was adequate for that - or else it would have been 'dig up t'garden and path' time...)

If you run the SWA now, then you can terminate the garden end in a waterproof box, wrapped in a plastic bag, with a bucket over it... - it'll be fine.

rajanm

Mickey666 said:

Jeepers is right about SWA cable sizes - think carefully about future proofing, because upgrading a cable in the future is a lot more expensive and disruptive than paying a little extra now for a large cable.  If it's a long run to the shed then I'd probably go up to 6mm2 SWA.

As for a pull cord when laying ducting, yes that's a good idea but not too big a problem if omitted.  An electrican's 'snake' (a thick nylon core) can be used to push right through the conduit to the the other end and then pull the cable through.  Alternatively, tie some light string around a suitable piece of cloth and stuff it on end of the conduit.  There should be enough cloth to create a decent seal but not enough to be tight.  The connect a vacuum cleaner to the other end of the conduit (duct tape can be your friend for this) and switch on.  The cloth + string should then be sucked along the conduit to the other end.   The light string can then be used to pull another, stronger, string/rope through the conduit.

Incidentally, although called a 'pull cord' it should not be used alone, especially with a thick and stiff SWA cable.  There should be someone pushing the SWA cable into the conduit at one end and another at the other end gently pulling the SWA through.

The distance is around 30 metres and we have an outside socket at the back of the house so perhaps the electricity cable could run off of that?  If we don't take the opportunity to do this now then I'm guessing our only other option is to run an above surface cable which I guess could look pretty unsightly?

Ajmason42

We used mains water piping laid under our patio as fairly cheap from t/station or screws fix and end stops are easy to buy.. put more in than you think you’ll need as other have said good to keep data and power separate