Whilst I have my own thoughts on this, I know there are many of you who will challenge opinion to help me to strengthen my views, so here goes:

We are working as a contractor in an occupied block of flats. We have hired a diamond driller to create some core holes. Not once but twice now the DD has drilled though live cables. The PC has told us we need to get an electrician to repair, which we have done.

In terms of liability, who is responsible or is responsiblity shared, for the damage. Bearing in mind no one was hurt, but some one could have been.

This is a bit like driving a car at night with the headlights off. If you hit something then it's your fault. The DD should have satisfied themselves that there were no services in the area they were drilling. That being said, it has happened where services are present in places where they shouldn't be and that's a whole new ball game.

Was the wiring for final circuits?

Was it in safe zones?

If so the drilling contractor should have known this and refused to drill.

If not then the wiring should not have been there.

Who instructed the team where to drill - the PC, their contractor (you), or the supervisor of the sub-contractor (the DD team)?

As the lowest link in the chain I will claim "just followiing instruction" as subbie you signed off my RAMS

As the highest link in the chain did I provide sufficient information AND ensure suitable controls were available BEFORE making holes? Did I consider that you would hire in specialists?

As the middle link on the chain I am in for a kicking from both sides as PC and subbie assume I know what is going on - I am taking the money for the job ergo it is my duty to clearly communicate the task to those I contract to do the actual work.

a.k.a. "Follow the money" the PC contracted you to do the work you are liable to the PC, you may have recourse to the DD team but it depends upon your contract with them i.e. did you ensure there was back to back professional indemnity for the task you asked them to undertake

Edited by user 19 February 2018 21:19:43(UTC)  | Reason: added follow the money

Who is responsible for the damage would be approximately the last thing on my mind.

Thank you for responses so far. Just to hopefully, cover some questions asked:

1. No-one was injured during this episode.
2. The hole was drilled through a concrete floor, not wall
3. It is being carried out in an older building - not a new build.
4. We have not been given service drawings. In these older properties it is higly unlikely we will receive these - even where we do, they are most likely not kept up-to-date.
5. The wiring cut was the lighting.

Originally Posted by: WatsonD

Thank you for responses so far. Just to hopefully, cover some questions asked:

1. No-one was injured during this episode.  - thank goodness for that!
2. The hole was drilled through a concrete floor, not wall - from one flat into the one below?
3. It is being carried out in an older building - not a new build.  - Safe zones have not changed for 18 years now
4. We have not been given service drawings. In these older properties it is higly unlikely we will receive these - even where we do, they are most likely not kept up-to-date. - This is a shame, but sadly true.  An argumet for preliminary investigations to be paid for by the client then, time for a change and get services surveys done, in the same way as asbestos surveys are done, and ensure that the client get hit in the pocket for not being responsible and keeping their documentation up to date.
5. The wiring cut was the lighting. - So, in the flat below then?

So, IMHO the person with the drill, should have checked both sides of the “thing” that they were drilling through, this would mean looking at the floor “upstairs” and the ceiling, “downstairs”, this would not tell them where the lighting cable was, but, if there was a light in the room, then it would be reasonable to believe that there is a cable in the ceiling somewhere, unless it was surface run, in trunking or conduit, then it would have needed to be scanned for. However, it is reasonable to expect a cable supplying a light somewhere in the ceiling.

Now if, the cable was on the surface “downstairs” then the person with the drill needs a serious talking to.

If it was just a single cable supplying a single pendant in a room, if that is wired in steel conduit you may well have a job detecting the current flowing through the wiring to the pendant through the earthed steel conduit.

Are your DD company a demolition company if so they should be working to BS 6187 BS for demolition and this states that they will carry out various checks for service isolations prior to demolition or refurbishment.

In regards to blame it will depend on what information has been provided and how accurate it

 is.

I would also imagine this work will fall under a permit to break ground. If so this may be issued by

the PC and have various references to HSG 47 and cable avoidance tools. This would then put a bit more blame on the permit issuer and receiver as they should have checked all the condition of the permit were met before commencing.

If not then maybe this sort of work should fall under a permit to break ground in future,

as who is to blame / responsible shouldn’t be the focus, it should be more about how you can stop it happening gain.  

Originally Posted by: Gareth Chester

Are your DD company a demolition company if so they should be working to BS 6187 BS for demolition and this states that they will carry out various checks for service isolations prior to demolition or refurbishment.

In regards to blame it will depend on what information has been provided and how accurate it

 is.

I would also imagine this work will fall under a permit to break ground. If so this may be issued by

the PC and have various references to HSG 47 and cable avoidance tools. This would then put a bit more blame on the permit issuer and receiver as they should have checked all the condition of the permit were met before commencing.

If not then maybe this sort of work should fall under a permit to break ground in future,

as who is to blame / responsible shouldn’t be the focus, it should be more about how you can stop it happening gain.  

I would not expect internal works on flooring to be covered by the description of breaking ground.

CAT will have difficulty with 230V very low current wiring encased in steel conduit, remember it's the EM field that they detect in wiring, and this is made up of the current and the voltage which is why they work on larger services cables even though they are often steel wire armoured.

Also SWA is very leaky when it comes to EMC and EMF, where as conduit is a much better screen.  Hence it much more difficult to detect the EM field from.

Originally Posted by: paul.skyrme

Originally Posted by: WatsonD

Thanks Paul. That realy helps. Just to recap

1. I wouldn't have been so blase had someone been injured.
2. It was in a corridor, but yes to the floor below
3. The only information on safe zones I can find is for walls, which is of no use in this circumstance - do you know where I could find detail on flooring? - there are none, that's why you can't find them
4. This took out the lighting on the whole floor below. - Probably due to it taking the lighting circuit protection out for the communal area lighting, that's why all the lights went out.  The individual flats should still have been OK?  Was it just the communal lighting?

We have been working with the DD to ensure a safer system of work, but it is a shame that we cannot eradicate the risk entirely.

Was the electrical supply they drilled through within the structure or surface mounted?

​​​​​​​

Yes just communal lighting; and yes, the cable was within the structure.