Is metal stud-work required to be earthed?

[Seb101]

Often wondered this. My current house is metal-framed throughout and I can find no evidence that the studs are earthed in any way. While they are not in themselves 'exposed' metalwork, the studs are often deliberately screwed in to for securing heavy wall items.

There are a lot of cables running through the walls, and I've discovered the cables often pass through cut-out holes in the metal studs with very sharp edges - it would not take too much mechanical action to cut the sheath of T+E.

 

[Taylortwocities]

....

 

[EFLImpudence]

The cables should be protected from any sharp edges but there is no requirement to generally earth metal studwork.

 

[Seb101]

Would you consider cables running through these kinds of punch-out without a grommet to be 'protected'?

 

[JohnW2]

The cables should be protected from any sharp edges but there is no requirement to generally earth metal studwork.

Indeed. Popcorn time, I fear.

Kind Regards, John

 

[JohnW2]

Would you consider cables running through these kinds of punch-out without a grommet to be 'protected'?

'Protected' by what? In the absence of grommets or somesuch, the answer surely has to be 'no', doesn't it?

Kind Regards, John

 

[EFLImpudence]

Would you consider cables running through these kinds of punch-out without a grommet to be 'protected'?

Not protected, no.

Whether they need protection is dependent, I suppose, on the sharpness.

 

[Seb101]

Well quite, and I doubt there is any specific measure of that for regulations.

House was wired to 16th Ed. in 2002 and has RCD protected sockets, but the lighting circuits are not and run freely through these studs without protection. I think I might get a CU replacement for peace of mind.

Am I right in thinking a fault connecting just the live conductor to the studwork would not be detectable by any sort of test unless there was an additional fault connecting the stud to earth/neutral?

 

[EFLImpudence]

Am I right in thinking a fault connecting just the live conductor to the studwork would not be detectable by any sort of test unless there was an additional fault connecting the stud to earth/neutral?

Obviously if you measured the studwork for voltage it would be detected.
If you mean detectable by any circuit breaker or RCD (with insufficient ground contact) then you are right.

I think you are probably worrying unnecessarily.
If your house is like this then so must millions of others be and
the cables aren't going to jump around on their own.

 

[JohnW2]

Am I right in thinking a fault connecting just the live conductor to the studwork would not be detectable by any sort of test unless there was an additional fault connecting the stud to earth/neutral?

As far as I can make out, that's essentially true - unless, I suppose, one's tests included going around looking for accessible heads of screws etc. which entered the studwork and measuring their potential. However, I don't imagine that anyone is going to do that.

It would take very exceptional circumstances for a 'live', but totally 'concealed' metal stud to do any harm (although accessible screws etc. which penetrated it could present a hazard) - although you will no doubt be hearing about one such high-profile case which had a tragic outcome.

Kind Regards, John

 

[Seb101]

Obviously if you measured the studwork for voltage it would be detected.
If you mean detectable by any circuit breaker or RCD (with insufficient ground contact) then you are right.

I think you are probably worrying unnecessarily.
If your house is like this then so must millions of others be and
the cables aren't going to jump around on their own.

Good point. I'll just wave my non-contact detector pen over the studs and rest easy.

 

[SimonH2]

Hmm, wasn't there a case a while ago where the studding became live due to a board fixing screw having gone through a cable - and it only came to light when some water pooled on the floor ?
Ah yes, here it was - one of those "chain of issues" which all had to happen to cause the fatality.
Short version: metal studwork, a board fixing screw went through a cable and made the studwork live, that persisted for some time undetected and without causing any problem, the boiler then leaked and formed a pool of water which contacted the studwork, the occupier knelt down to mop up the water and (I assume) then made a circuit between the live water and some earthed metalwork on the boiler, the electric shock was fatal.

 

[JohnW2]

Hmm, wasn't there a case a while ago where the studding became live due to a board fixing screw having gone through a cable - and it only came to light when some water pooled on the floor ? .... Ah yes, here it was - one of those "chain of issues" which all had to happen to cause the fatality. .....

It would take very exceptional circumstances for a 'live', but totally 'concealed' metal stud to do any harm (although accessible screws etc. which penetrated it could present a hazard) - although you will no doubt be hearing about one such high-profile case which had a tragic outcome.

Kind Regards, John

 

[EFLImpudence]

Yes, I am sure that was the case John had in mind.

So which of the "chain of issues" would be best to guard against to prevent the same happening again AND prevent something else happening more often?

Perhaps ban water from inside houses ???

 

[JohnW2]

Yes, I am sure that was the case John had in mind.

Yes. As I have indicated, it was!

So which of the "chain of issues" would be best to guard against to prevent the same happening again AND prevent something else happening more often? Perhaps ban water from inside houses ???

Since this event arose because of what I described as 'very exceptional circumstances', I think one needs to think very carefully before deciding that anything should be done "to prevent it ever happening again" - particularly if, as you implied, that 'anything' might well result in other risks (in other circumstances) increasing.

At least one person here might consider introduction of the death penalty for anyone penetrating a cable (let alone a cable and metal studwork) with a screw - or, at least, putting them in a dreadful prison for life, confiscating all their assets and sending their dependants to a workhouse.

Kind Regards, John