Looking for some advice on a job I'm doing right now. I'm about to build a 4m long 4 course high 4" block on-flat retaining garden wall. Behind the blockwork will be DPM, gravel + geotex for drainage, then soil. Front of wall will be rendered and will finally have 3x 240V surface mount lights fitted around half-way up from ground level. All supplied via a feed in SWA. To avoid ugly SWA and JBs at ground level + flex up the visible wall face, I was thinking of putting 20mm galv conduit and trouser boxes behind the wall to daisy chain the supply along behind, bringing the supply for each fitting from the box through the wall where it's needed (+ IP rated box at one end to terminate SWA to the daisy-chain). Trouser boxes would be filled with magic gel once wiring is done and tested, before lids screwed down and finally buried in the back-fill gravel. Anyway the questions are: 1) Anyone done this before - is there a better way? 2) Should I be embedding front-to-back conduit in the block wall courses as I build it or just drill through afterwards? Any advice welcome.
I wouldn't use galv conduit in the ground. Not sure why you would want trouser boxes, wouldn't through boxes be better? If you make off the SWA underground, you should use a torpedo joint, otherwise the SWA will corrode. If the fittings are below ground level, there's a possibility they will fill with water. Might be better to use flex through the wall and stuffing glands?
It is a bad idea to bury jointed cables. My advice would be to leave the trouser boxes accessible just above ground level on the outside of the wall so they can be accessed. PVC conduit would be better than galv steel but thats just preference. Otherwise what you propose is sensible.
Why can't you run it in swa and put your boxes at the back of the wall, near the top and finish the back-fill a few inches down, just clear of the cable and boxes? That's how I've done mine, as UP inferred, joints underground are best avoided if at all possible.
Thanks for the replies. Re-thinking this you're all right about avoiding burying any kind of joint - its just inviting disaster. I'll run the conduit and boxes just above ground level behind the wall, out of sight, and bring flex out via stuffing glands through the wall to the fittings. SWA was going to be terminated above ground anyway in an IP rated box hidden behind a trellis panel. I'll also sleeve the flex through the blockwork. Thanks for the point about daffodils - I'll suggest I fit a dimmer for the bulbs
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