Builder set cable into concrete with no conduit.

[Tayjen]

Hi,

We are having flooring and skirting put into a workshop/garage conversion. Last year our builder completed the main part of this job by fully insulating the room including damp-proofing the floor and covering with screed. Electrical sockets were also installed in two locations via a cable in the screed.

Today our carpenter (no connection to builder) started putting in skirting into this room however he called earlier to say he had drilled down into an electrical cable which triggered the RCD. Apparently the cable is sunk into the screed with no conduit and therefore gave no warning regarding drilling into it.

The builder has agreed to look into it and he is round at our house at the moment speaking with the carpenter.

The conversion has already been signed off by the council and therefore the electrician and we have all the certificates so my question is if sinking cables directly into concrete is a) legal and b) if they need digging up, the responsibility of the builder or not. Its obvious that its not best practice but I can't see what the legal status is.

I want to be prepared for a difficult discussion later so any direction here would be welcomed. Thanks in advance!

 

[JohnW2]

... so my question is if sinking cables directly into concrete is a) legal and b) if they need digging up, the responsibility of the builder or not. Its obvious that its not best practice but I can't see what the legal status is.

As you say (and have discovered), it's not a very clever practice. Regulation 522.8.7 of the current Wiring Regulations says "A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor". I can see there being discussions/arguments about whether or not drilling holes into a floor counts as part of the "intended use"!

As for responsibilities, I imagine that repair would only be the responsibility of the builder who did it if what he did was non-compliant with the regs - so everything probably depends upon people's views about the above.

Kind Regards, John

 

[stillp]

There's no reason why a cable should not be direct in the screed, but it should be run in the safe zones; along the bottom of a wall is not a safe zone, since it's possible for a carpenter to drill into it when fixing skirtings...

 

[JohnW2]

There's no reason why a cable should not be direct in the screed, but it should be run in the safe zones; along the bottom of a wall is not a safe zone, since it's possible for a carpenter to drill into it when fixing skirtings...

Are safe zones defined for floors?

Kind Regards, John

 

[stillp]

No idea. However I assumed the cable is in the wall, else how would the carpenter have drilled into it. I know, I know, never assume...

 

[JohnW2]

No idea. However I assumed the cable is in the wall, else how would the carpenter have drilled into it. I know, I know, never assume...

Maybe. I suppose I also made the mistake of 'assuming' since I assumed that "the carpenter drilled down into a cable" implied drilling into the floor. I've never noticed any safe zones defined for floors, but I've never had any reason to look for them, since I've never had any cables buried in floors - so maybe they do exist.

Of course, if you're right and the carpenter drilled into a cable in the wall, then it's quite possible that it was in a safe zone - e.g. created by a socket above - in which case the finger of responsibility presumably would point at the carpenter!

Kind Regards, John

 

[Tayjen]

... so my question is if sinking cables directly into concrete is a) legal and b) if they need digging up, the responsibility of the builder or not. Its obvious that its not best practice but I can't see what the legal status is.

As you say (and have discovered), it's not a very clever practice. Regulation 522.8.7 of the current Wiring Regulations says "A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor". I can see there being discussions/arguments about whether or not drilling holes into a floor counts as part of the "intended use"!

As for responsibilities, I imagine that repair would only be the responsibility of the builder who did it if what he did was non-compliant with the regs - so everything probably depends upon people's views about the above.

Kind Regards, John

Yes, I had found that reg but I can see it being debatable.

Apparently he is going to put in a new junction box. Not sure what that means though at this stage.

 

[Tayjen]

No idea. However I assumed the cable is in the wall, else how would the carpenter have drilled into it. I know, I know, never assume...

Maybe. I suppose I also made the mistake of 'assuming' since I assumed that "the carpenter drilled down into a cable" implied drilling into the floor. I've never noticed any safe zones defined for floors, but I've never had any reason to look for them, since I've never had any cables buried in floors - so maybe they do exist.

Of course, if you're right and the carpenter drilled into a cable in the wall, then it's quite possible that it was in a safe zone - e.g. created by a socket above - in which case the finger of responsibility presumably would point at the carpenter!

Kind Regards, John

Yes, I haven't quite worked out why he was drilling to the screed either. I thought the skirting got fixed to the wall. He is also boxing in the pipes in the corner, but they aren't too close so I'm not sure if it has anything to do with that.

 

[JohnW2]

Yes, I had found that reg but I can see it being debatable. ... Apparently he is going to put in a new junction box. Not sure what that means though at this stage.

To clarify the point being discussed by stillp and myself, did he drill into the cable in the floor or the wall - and, if the latter, was there any accssory (e.g. socket) above the point of drilling that would have created a 'safe zone' in the wall?

Kind Regards, John

 

[Tayjen]

As I understand it the cable was in the screed so he must have been drilling down into it. That's all I have to go on at the moment.

I know the cable was running from one socket to the other under the floor so it would have probably been directly under the socket.

I'll find out more in a couple of hours when I'm home and can see it first hand.

Thanks for your input.

 

[JohnW2]

As I understand it the cable was in the screed so he must have been drilling down into it. That's all I have to go on at the moment. I know the cable was running from one socket to the other under the floor so it would have probably been directly under the socket. I'll find out more in a couple of hours when I'm home and can see it first hand.

Fair enough. Had the drilling been into a wall, and within a 'safe zone' created by a socket vertically above, then, as I said, I think it would all (includibg any consequent ripping up of floors) be down to the carpenter for drilling without care into a safe zone which he should have realised might contain cables. However, if he drilled into the floor, I think that it's probably all largely dependent on the debate about the interpretation of 522.8.7 - and, regardless of that debate, would probably not be down to the carpenter (either the builder who buried the cable, or 'no-one to blame').

Kind Regards, John

 

[Tayjen]

It turns out the cable damage was in the floor of the WC on the other side of the wall, not the main room. This is the link off the ring main in the kitchen to the workshop conversion. (The WC and adjoining hallway is all part and parcel of the conversion). It looks like the carpenter was drilling holes to fit the boxing into and he's gone right through it. There is a temporary solution in place so he has power to finish the job.

Now, to avoid a dangerous situation in case of a spillage (which is quite likely at some point it being the location it is) the solution has to be 100% waterproof. What do you think would be the prudent solution that I should insist on? Are there any regulations (or reasonable interpretation of) regarding wiring underfloor to a WC?

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• Tayjen
• 16 Sep 2013
• 1

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• Tayjen
• 16 Sep 2013
• 1

 

[RF Lighting]

A resin joint kit is the only acceptable way of properly repairing that cable.

 

[sparkwright]

Hardly good practice to bury an unprotected cable so shallow, and in a place so vulnerable to get damaged. In an ordinary room, a carpet gripper could be nailed here - in this case a boxing is being fixed here.

You could dig out a bit more of the cable at both ends, cut the damaged bit, and fit two junction boxes with a short piece of cable in the middle.
The junction boxes would be placed into the boxing. Maintenance free junction boxes, as it looks like they will be unaccessible.

Just noticed your insistence on waterproofness, I suppose weather proof enclosures would satisfy that requirement.

 

[mfarrow]

It looks like the carpenter was drilling holes to fit the boxing

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• Tayjen
• 16 Sep 2013
• 1

In which case you could bring them up into a maintenance-free junction box(es) and put some suitable mechanical protection over the cable/joint.