Re wire, to cap wires or not

[Neale]

Hiya , just popped over from the Tilersforums where I am a Mod. A friend of mine has had his house rewired, On seeing the incomplete works last weekend I was concerned that all the new wiring has not any protective capping plastic or metal. the builder seems to say he can plaster right over them. In places I think he will struggle to even cover the cables as they are very close to the surface. i would have liked to see them sunk deeper.. What are the legal requirements ? Most of the cables are in 2 loft bedrooms and down the hall, stairs and landings. ?? Thanks guys.

 

[Rockingit]

Slight grey area, here. There isn't a requirement, per se, that they HAVE to be capped, just afforded mechanical protection. It's common to cover a cable in capping as it makes the job easier, frankly, and protects the cable from the risk of the plasterers trowel catching it, but pretty much once it's buried, it's buried.

If it's less than 50mm from below the surface then it needs to be protected by a 30mA RCD (there are a few exceptions to this, but generally this stands). And also of course that they have to run in the approved zones (vertical and horizontal from outlets).

Personally, for the sake of a few pence on some capping, get the job done right, and if that means running some shallow chases into the walls then so be it.

 

[Neale]

These cables are pretty much flush with existing walls. i think its a case of laziness by not chasing the walls out deep enough. I doubt you could get a covering of plaster in most places of 2mm.

 

[malcolmsanford]

Really there is no regulation that exactly covers this scenario

Regulation 522.5.1 covers the cable against corrosive or polluting substances. Most modern day plasters no longer affect the PVC in cables and so there is no need to cover them. If the plaster was perhaps an old Lime base type or even daub and wattle then yes I think you should have protection. What type of plaster is it.

Regulation 522.8.1 covers really just damage to the cable in general but again highly unlikely this could be evoked is this circumstances, the sparks though will look a little stupid if after plastering you can see the outline of the cable and so it's more a practical thing.

Regulation 522.6.6 covers depth of cable, and in this case as it is buried less that 50mm from the surface the circuit will require additional protection, and the electrician would seem to have chose an RCD to do that

 

[stansmith]

good post, ive also heard that the plaster itself can slowly destroy the insulation on the cable not sure if thats the case anymore but i wouldnt want to risk it and as^^^ said its good to protect from the plasteres trowel, the last thing you want is nice smooth newly skimmed walls and then try to energise the circuit and bang! or for it to fail insulation tests and have to tear away the new plaster for the sake of a couple of quid and an hour or two fitting it it seems silly not to tbh

 

[Neale]

Thanks Malcolm, I think there will be issues with the cables showing. There has been no attempt to clip the cables back or even flatten them out....just a twisted mess ! just trying to make sure my mate doesn't get fobbed off.

 

[stansmith]

tell your mate he needs to have a word with the builder tell him a few of the regs malcolm mentioned will scare him into doing it properly sound like the builder/sparks a chancer need to put him straight and get it done properly

 

[Mark_Burgess]

It sounds like you will get a job to tile the whole house to cover the rubbish on the wall!!

Seriously though, your mate may want to bring in the plasterer and the supposed electrician in and get them to both talk about it. The plasterer will be on your side of the argument in that capping will give some protection.

Also with it barely being covered of 2mm, it will surely flake of the wall in time.

 

[Knobhead]

Old plasters were high in sulphides which will attack copper. So a plasterer nicks a cable and you ended up with copper sulphide growing out of the wall. You can tell if this is happening by bulges in the wallpaper in line with the cable as the copper sulphides grow. Copper sulphide has a lower density to the original plaster and therefore takes up more room hence the bulge. To add to the fun copper sulphide is conductive so the wall becomes live.
Capping as far as I recall was a defence against over enthusiastic plasterers. There must be 100’s of walls electrically live under the wallpaper. (Can’t beat paper for insulation!).

This has got me interested now as I worked for one of the major manufacturers of plaster in the UK and still know people in the research departments.

A few phone calls are in order.

 

[oxocube]

Cappping is not required and plaster must be a minimum thickness (10mm ish) to avoid cracking. This means cables always need to be chased below the surface of the brick/blockwork to ensure decent depth of plaster.

 

[PigletJohn]

Old plasters were high in sulphides which will attack copper.

Unlike Tony, I can't see that plasters would attack the copper in modern electrical cables, since they are insulated in (usually) PVC and then sheathed in more (usually) PVC.

So unless someone cut through both the sheath and the insulation, which takes a bit of effort even with a sharp stanleyknife, the plaster would not come into contact with the copper.

Plain MICC cable (fire-resistant with a copper cover) might be vulnerable, but it was generally surface-mounted, not buried in plaster, and these days it too has a protective (usually orange) plastic sheath to prevent chemical attack.

I can imagine though that copper pipes might have corroded if the plaster was aggressive.

 

[PigletJohn]

BTW (sorry) all the spreads I ever asked said that they take great care of their trowels, and would never risk nicking the edge by letting it dig into a cable.

 

[Brendan976]

I also plaster, and in the ideal world capping would be best but its not mandatory. Nearly every plasterer will take care over cables (bodgers excepted) as a decent Marshal town trowel is £50-£60. One small nick or god forbid a blown hole in it is the end of that trowel until you can get is refaced. Then you have the task of wearing it in for that just right finish.

Ben

 

[Essexboy7]

Yeah but make sure the person doing the capping isnt a complete lemon who puts a capping nail through the cables!!!!!!!!!!!!!
I had that happen to me on a job before.A rush ,rush rewire with no time to do IR and BANG when the ring got livened up

 

[telectrix]

well, what do you expect in essex?

 

[amlu]

fill your chases and around the boxes with some bonding coat before plastering