twin and earth between block wall and dot dab - cable channels needed?

[Deuce]

Hi all,

Our sparky has carried out first fix, twin and earth cables clipped to the block walls of our extension routed to each back box. His leaving instruction was to dot n dab the plasterboard over the cables - but he has laid them without plastic or steel cable channels and in such a manner that I'd have to re-route many of them to fit within channels.

Is it actually a requirement to use channels or is it fine to just put the plasterboard directly over the cables? I'm obviously thinking it's going to make it very easy for someone in the future to have a 'shocking' experience putting up shelves.. but much as I google the question I see many suggesting no protection or plastic channels - which of course a drill bit would shoot through anyway. I personally use a detector but I guess most do not.

What do the regs say about this? Elsewhere in the house I have found steel channels used, I can see the sense in them but in this instance, using them would pretty much require starting again.

Thanks in advance for any help.

 

[Deuce]

A couple of photos to illustrate. The vertical cables could be put in channels with a bit of tweaking but the horizontal cables won't fit and would need re-laying to adjust sufficiently. Tbh I was surprised upon my return that he hadn't sent them through the joists above which were fully exposed at the time, which would have left just the vertical drops to each box to worry about - where future diy'ers might expect the cables to be. As it is the cables run around the top of the room in the same place someone might choose to put up a curtain rail.

 

[Pretty Mouth]

Capping is used to protect cables at the plastering stage, it's not considered to protect them afterwards. It was used a lot when wet plastering was commonly used, but not so much since dot'n'dab became commonplace. It's not a requirement of the regs to use it anyway.

Running the cables round the top of the room like that is compliant (there's a 150mm zone at the top of the wall where it meets the ceiling that they can be run), but most sparks prefer to run them in the ceiling void where feasible. It does seem strange that your spark didn't take the opportunity to do this, it being accessible at the time of installation.

The only non compliant thing I see in the photos is in photo 1 - where the cables drop down and through the wall (presumably to external lighting), they are run outside permitted zones. To be fair to the installing spark, this can be difficult to achieve without having cables on display

 

[ipf]

The 'channels' you are talking about are cable capping. It is to protect the cables during plastering.
As long as the cables are run in the correct zones, which they seem to be, there shouldn't be any problem with dot-dab.

edit......as explained in the above post by the bloke with the handsome gob........who beat me to it.

 

[Deuce]

Capping is used to protect cables at the plastering stage, it's not considered to protect them afterwards. It was used a lot when wet plastering was commonly used, but not so much since dot'n'dab became commonplace. It's not a requirement of the regs to use it anyway.

Running the cables round the top of the room like that is compliant (there's a 150mm zone at the top of the wall where it meets the ceiling that they can be run), but most sparks prefer to run them in the ceiling void where feasible. It does seem strange that your spark didn't take the opportunity to do this, it being accessible at the time of installation.

The only non compliant thing I see in the photos is in photo 1 - where the cables drop down and through the wall (presumably to external lighting), they are run outside permitted zones. To be fair to the installing spark, this can be difficult to achieve without having cables on display

Thanks - much appreciated peace of mind!

Out of interest what is it about the cables going down and through the wall that is wrong? they would have to drop the same way if they were going to a socket/light switch. Is it that they then cross the cavity?

 

[DPG]

Thanks - much appreciated peace of mind!

Out of interest what is it about the cables going down and through the wall that is wrong? they would have to drop the same way if they were going to a socket/light switch. Is it that they then cross the cavity?

It's because they not in a prescribed zone. If they ran down to switch or socket then that would create such a zone. Havd a Google search and you will be able to find a diagram explaining the zones.

 

[Electro-tech]

I think as you said the cables could have been installed through the joists when exposed, either way, if you or someone at a later date need to access the cables for any reason it won't be possible. Obviously, if there is a removable floor above the ceiling then that would be great. You may be able to pull a cable out of a vertical capping or channel as well at back boxes. Just remember when hanging things on the wall as there is not much cover depth. Sorry to be an old woman stating the obvious.

 

[7029 dave]

It's because they not in a prescribed zone. If they ran down to switch or socket then that would create such a zone. Havd a Google search and you will be able to find a diagram explaining the zones.

This is where it gets a bit silly IMO, you just cant avoid these situations, to keep compliant chop in a shallow box and blanking plate there is your prescribed zone, but who's going to want that.
Just having a moan Daz off the beer trying to lose some timber. lol

 

[James]

Prescribed zones project to opposite side of wall.
therefore if there is a light outside, you may reasonably expect a cable to run vertically on the other side of the wall.

 

[Pretty Mouth]

Prescribed zones project to opposite side of wall.

*where the wall thickness is <=100mm

 

[timhoward]

The only non compliant thing I see in the photos is in photo 1 - where the cables drop down and through the wall (presumably to external lighting), they are run outside permitted zones. To be fair to the installing spark, this can be difficult to achieve without having cables on display

I sometimes put a token bit of galv channel over drops like that. I know that it won't last long against a determined drill but it might make the bit slide long enough to make someone stop and think.

Prescribed zones project to opposite side of wall.
therefore if there is a light outside, you may reasonably expect a cable to run vertically on the other side of the wall.

That's why my house looks like this:

But seriously, there's a wall depth limit too.

 

[DPG]

This is where it gets a bit silly IMO, you just cant avoid these situations, to keep compliant chop in a shallow box and blanking plate there is your prescribed zone, but who's going to want that.
Just having a moan Daz off the beer trying to lose some timber. lol

'Off the beer' is not a phrase I like the sound of!

Had a nice couple of pints of Dancing Dragonfly yesterday at the local spoons. A nice ale that one.

 

[ipf]

Prescribed zones project to opposite side of wall.
therefore if there is a light outside, you may reasonably expect a cable to run vertically on the other side of the wall.

Better have a look outside to see if there's a light anywhere before you hang that picture, eh?

 

[superspark]

Prescribed zones project to opposite side of wall.
therefore if there is a light outside, you may reasonably expect a cable to run vertically on the other side of the wall.

We normally fit metal capping or oval tube, its just if you do have damage you have some chance to pull through, but only sparks seem to be aware of 150mm from ceiling, .. i personally think he is so booked up, they just tacked the ceiling,
I dont no any sparks would wire like that when they could have gone through joists.

 

[brianmoooore]

I think as you said the cables could have been installed through the joists when exposed, either way, if you or someone at a later date need to access the cables for any reason it won't be possible.

There is likely to be some colourful language if a future spark pulls up the floor above to access cables, and not one in sight!

 

[cliffed]

Find it easier to use metal channeling it keeps the cables in place…but like all have said nothing wrong in not using it…obviously all cabling will be protected by rcd/rcbo’s

 

[7029 dave]

We normally fit metal capping or oval tube, its just if you do have damage you have some chance to pull through, but only sparks seem to be aware of 150mm from ceiling, .. i personally think he is so booked up, they just tacked the ceiling,
I dont no any sparks would wire like that when they could have gone through joists.

I did exactly that when converting my integral garage. Above was the third bedroom all laminated floor did not want to pull that up.
All services were in the garage so it weren't too bad, just quite a bit of chasing 150mm from ceiling all by hand most of it was internal block work. External wall was hard brick an rendered.

 

[Deuce]

*where the wall thickness is <=100mm

Thanks, good to know the regs, although - as below...

This is where it gets a bit silly IMO, you just cant avoid these situations, to keep compliant chop in a shallow box and blanking plate there is your prescribed zone, but who's going to want that.
Just having a moan Daz off the beer trying to lose some timber. lol

That was what I thought when this thread first educated me about the zone being created only when there is an obvious fixture for the cables to be routed towards. I must have seen hundreds of exterior lights that can only be supplied by cables run in this way but no one is putting a blanked off box on the inside of the wall.... Has anyone ever seen this actually done? I can imagine a very particular spark perhaps suggesting such a thing, but I can't imagine their home owner customer liking the idea!

Sorry you're off the beer by the way. Sounds none compliant to me!

 

[Deuce]

Find it easier to use metal channeling it keeps the cables in place…but like all have said nothing wrong in not using it…obviously all cabling will be protected by rcd/rcbo’s

I have drilled through a live before. Big bang and a moment of confusion - but yes, the circuit was de-energised instantly. I have since used a detector, they may be crap at accurately locating studs and pipes but they're very good at detecting a live cable.

On reflection, using boxes to define zones based on the theory it will give future diy'ers a vague clue as to where the cables are probably puts people off bothering to use a detector to make certain - which I believe they should. Not because there is much chance of a serious shock, but because there is a very great chance of falling off a step ladder, stumbling, dropping your drill or soiling yourself when it happens..