SWA burial depth under patio flags

maxinc · Aug 22, 2014

Hi everyone,

I am digging the trench for 25-30m of 3x6mm SWA from my house's CU to the (yet to be installed) summer house. 95% of the length will be under a new stone patio. This is part of a major back garden landscaping project which I challenged myself to do on my own (most of it anyways). The electrical connections, testing and certification will be done by a qualified electrician.

The problem I have at the moment is that I hit a particularly tough and compacted layer of stone / concrete / rubble at about 35cm depth. Other than sparks from the pick axe and a colourful language, I am really struggling making progress.

I was initialy aiming for 400-500mm depth but I am now wondering if 350 would be suffient in this case. I'm pretty confident the cable will be safe from any forseable mechanical intervention, short of a power digger and a over enthusiastic operator ignorig the tape.

The SWA will be inside a 32mm "heavy duty" PVC pipe together with 2 x outdoor grade Cat6 STP cables and a pull rope. This will sit on a thin bed of sand, followed by more sand, 10-15cm of compacted Type 1 sub base, Yellow warning tape, 5cm sand cement mixture and 3cm of paving flags.

Your thought on this are greatly appreciated.

Best,
Andy

telectrix · Aug 22, 2014

fine in my book. there is no set depth specified, just that the cable be deep enough so as not to be subject to damage . where digging might be expected, you'd bury the cable 18" or so. under slabs there's no likelyhood of digging taking place, so a shallower depth is sensible.

maxinc · Aug 23, 2014

Thank you very much! This will make my life a lot easier

dingledong · Aug 23, 2014

Another I will do it all myself and just get an electrician to sign it of

maxinc · Aug 23, 2014

dingledong said:
Another I will do it all myself and just get an electrician to sign it of

Excellent observation! I wonder what tipped you off? Could have been the DIY forum or my explicit description?

I also do CCTV, Alarms, IT&C, Home automation, AV integration, clean, cook and do my own laundry among many other things. Maybe with less of your judging attitude you'll get to do more as well as it can be quite rewarding.

Attitude aside, I thought that digging treches is a builders job, not an electrician's, unless the electricians are trying to do it all these days

telectrix · Aug 23, 2014

fair comment. if, as you say, you're just doing the groundworks and laying the cable: if it were me doint the electrical work, i'd want to see the cable installation and test it before the trench was filled in. any problems could then be addressed before filling and rectified without having to dig it all out.

dingledong · Aug 23, 2014

Yes your skills are amazing just need to keep up with the spelling maybe
But your still not an electrician though are you

maxinc · Aug 23, 2014

telectrix said:
fair comment. if, as you say, you're just doing the groundworks and laying the cable: if it were me doint the electrical work, i'd want to see the cable installation and test it before the trench was filled in. any problems could then be addressed before filling and rectified without having to dig it all out.

In an ideal world I would employ electricians, builders and landscapers to the job the best they can but unfortunately I don't have the resources for all that and this project would have never happened otherwise. I decided to take the back breaking work on my own and leave the specialised bits to professionals, like terminating the long chunk of cable and installing the sockets etc. All cabling is surface mounted in a 3 compartment trunking easily inspectable. I am taking detailed pictures of everything as I go along and I want to make sure I'm doing it right, hence asking professionals before pouring concrete in. In in the unlucky eventuality that the cable turns out to be faulty, it should be possibe to replace without digging it out, hence pvc pipe and pull rope.

I don't mean to offend anyone and I appreciate all the honest and professional advice. I am a professional myself and enjoy offering advice in my area of expertise.

I will ignore offensive and irrelevant comments such as the above, I hope the admins deletes them as they don't add any value to this discussion.

Thanks again for answering my question.