Twin & earth cemented into wall

Hi all, I’ve discovered some twin & earth cabling directly cemented into walls for some of my light fixtures, i.e. not inside a conduit.

Is this legal? If not, was it ever? What now?

As far as I understand surfix is okay for this, but twin & earth?

Most electricians don’t know the difference :skull:

To my knowledge it is legal to install “under plaster”, but you may not bury it in concrete (aka the floor).

This old Aberdare pdf from July 2012 says yes.

If you go to the website now, see link, it doesn’t seem to say so anymore:

Both leaflets refer to section 6, clause 6.3.6, which is for ROUND twin and earth cables WITH METAL STIFFENING. PVC insulated multicore cables with a bare earthing conductor
and round cable with metal stiffening (the indication seems to be either is allowed).

So… seems the answer is NO YES…

Note: Edited to change NO to YES, I misread the SANS regulation and thought it must be round wire with metal stiffening. I also read that in a few other places, so I didn’t question it.

aberdare_leaflet.pdf (182.4 KB)

The exact wording in the 2017 edition is:

6.3.6 PVC insulated multicore cables with a bare earthing conductor and round cable with metal stiffening The cables may be installed
a) on the surface
b) under plaster

The way I read this is that both “multicore cables with a bare earthing conductor” as well as “round cable with metal stiffening” may be installed under plaster, i.e. both surfix and twin-and-earth can be installed under plaster.

Edit: The fact that Aberdare states that their flat twin and earth cable complies with clause 6.3.6 seems to validate this interpretation.


You’re right, now that I look at it again, it does say OR.

Strange then that the newer aberdare spec sheet doesn’t say it anymore while the older one did.

I know the American code says that in this case you’re supposed to follow the instructions of the manufacturer as a last resort, which would then mean that if it is spec’ed for under-plaster install you can do so.

I will edit my post and correct it.

I suspect it might be because installing wiring directly under plaster is generally not a great idea, and they’ve come to the realisation that they don’t want to be seen as condoning it.

PVC conduit is not going to protect against a nail driven into the wall, but if that has happened one would at least be able to pull through new cables.


My experience is that you need to instruct the electrician to do this. For them it’s more work…
I also find I have to rewire their regular GP wiring (and end up with a coils of spare wire)

Safety wise I think there is no difference. PVC is PVC. Also, if you lay the cable horizontally up or down (where you expect it to be when drilling holes), it should be no more of a problem than conduit. But indeed, if you do end up hitting it (I am paranoid, I have the electronic avoider tool for that reason!), conduit is a whole lot easier to work with. Also, if you have to chase channels in the wall anyway to lay the cabling, you might as well lay conduit. It is cheap enough.

But in @mariusm 's case, at least it means he doesn’t have to go dig them all up and replace them!

Thanks y’all.

Yeah, that was my fear. Already have quite a list of things that REALLY shouldn’t be the way they are.

Busy replacing light fittings and it was just “Oh, what fresh hell is this?”.

Not picked up when the CoC was done when you bought the place, right? :slight_smile:

Nope. But it’s not even limited to electrics…

I’ve ripped out the intercom and cameras already, everything was super flaky. And most of the cables also directly under plaster, meaning I couldn’t even use them as pull-wire.

A lot of the stuff wouldn’t even be more difficult to just do correctly in the first place, but now costs a lot of time to fix.

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In my recent house renovation the plumber removed all the galvanised pipes and replaced these with PEX(?) piping. This is flexible piping that uses regular brass compression fittings.
This is also plastered into the wall and you have no idea where it is routed.
When I was in Europe I checked their installations and they do likewise but they use a sleeve over the PEX pipe. This allows you to remove the pipe if required.
In SA it looks like we’ve dispensed with this precaution.

It probably has something to do with likelihood of replacement due to freezing or so-on, or additional insulation.

But yeah, it’s difficult to spend more now in materials if it’s only the next owner that will benefit.

We never had this precaution to begin with. We’ve been plastering copper and steel piping into walls for decades with no sleeving. All we did was move to PEX (which is a really great solution, and much cheaper).

You can find pex in the wall as easily as you can other pipes (with a pipe/stud finder).It doesn’t corrode like copper or steel does (although the compression fittings can, if you have a leak). Acidic water doesn’t eat PEX, but it does eat copper. Also, copper pipes are in lengths of 5.5 meter (if I recall) and for long runs you will have several joins. PEX is a long roll and you have no joins on a long run.

The only issue is that where piping is visible and where an OCD eye wants to see a straight line, PEX looks a bit cheap. Even then, hiding PEX inside plastic trunking is sometimes an option.

I absolutely love PEX.

Edit: I need to expand a bit about my pipe-finder comment. Yes, the pipe is plastic (polyethylene), but while it is full of water a good pipe/stud/metal finder sees it. My Bosch Truuvo finds pex pipes with no problem at all.

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It’s even softer than copper. I was drilling into the wall in my roof cavity and a PEX pipe rubbed against the chuck. Next thing there was a spray of water…

The wife tells me, I want this mounted, here, on that wall … in the bathroom.

Do it now.

After using exceptional skills to figure out where the pipes should be, a very long time before any Bosch Truuvo’s, the operation starts. Wife is overseeing it with a female’s attention to detail.

I drill and drill, drill not moving, blerrie clinkers in the brick again. Push harder, next moment, me barefoot in the bath with an electric drill howling, I’m being hosed by high-pressure ice cold water.

The drill is thrown that way, I go straight up clear over the rim of the bath like a pro.

An entire weekend without water with 2 babies in the house, the pipe was copper and we needed new tiles too.

Needless to say, to date, I have not been instructed to drill anything into any bathroom wall. Jip, not once.

Same house, newly built extension, I do the work to put in the lightswitches. I chisel a nice neat furrow in the wall for the wires all over the house after we carefully deliberate (fought the shite out of each other) where they should ideally go, and push the wires in, ready for sparkie to check the next day before we close up.

He comes around, sees my master craftmanship, and calmly says: Nope, wires shall be in an electrical conduit, and walks off.

Yeah, I had a moment like that too. In my garage thankfully. I used a chisel to open up the wall, then set about finding a plumber. One very kind gentlemen came around on a Saturday afternoon to fix it. Couldn’t even blame the wife for it…

I left that hole in the wall for the better part of a year before patching it up. Then I left the grey spot on the wall for the better part of a year before painting it… :slight_smile:

After that incident I didn’t touch a drill for a while until day-zero stuff came around and I needed to put some pipe (PEX pipe too!) through a wall. A bathroom wall (tank water from one toilet to the one next door). Bathroom walls are full of pipes, especially in the vicinity of the porcelain throne. I went to a tool place, rented a drill and a pipe-finder…

Soon afterwards I bought my own pipe-finder. And then a proper SDS drill. And now I’m no longer scared to drill. The only trouble with the pipe-finder: False positives. Sometimes it beeps, but if you sweep the area around it you quickly figure out that there is no pipe or wire running there… there’s just a piece of rock or something that it is picking up. Then you drill… carefully :slight_smile:

Edit: The pipe/wire finder also doubles as an excellent last-minute “is this wire actually dead?” checker.

:rofl: I’m not blaming the wife, I just got out of the chore of drilling in bathrooms, all her own doing. Did not have to say a word.

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