Electrical Question

Electricity in the loft

Hi,

I just had my house rewired and I have several question about the quality of the work.

As we had the whole wiring done, they installed all cables for the 1st floor in the loft on top of the beams. I asked them why they didn't drill into the beam to allow me to do floor in my loft. They told me that they couldn't as it was due to regulations and they have to go on top.

For the light in the loft, do we need a separate ring or can we use the ring from the 1st floor.

I want to make sure that the job has been seriously and they don't try to give me stupid excuses.

Thank you very much for your reply.

Greg

5 Answers

Best Answer

Safe zones dont really apply in lofts but I wouldnt drill through the joists unless i had no other option and only once maybe, in case, like ive done before, put new plasterboard over the top of the old ceiling and screwing the board would be dodgy if the cable were through the joists, plus as the joints are usually smaller, it would weaken them. Some old houses are 2in X 2in
If I had been wiring up in the loft I would have asked you whether you are likely to board the loft. If you were, I would have run the cable round the edge and along the line of the joists and not over them. Would have used slightly more cable but not much. Would have been less than a tenner extra.
You could always screw extra timber down over the joists to get round that problem
Run loft light off 1st floor lighting radial circuit or off a socket ring or radial circuit with a 3A spur fused connection unit. I always advise to have smoke alarm in loft as well.

Answered 12th Apr 2013

Arbela

Member since 10 Apr 2013

Its normal practice to clip the cables on top of and/or directly onto the sides of the rafters and other wooden beams in the loft. This is because unlike the floor joists at ground to 1st floor level they are a lot thinner and would be seriously weakened if substantially drilled (e.g. 20/25mm holes).

For a standard 100watt loft light, its again standard practice to incorporate this light on the upstairs lighting circuit, as running a separate dedicated circuit for a single light would not be cost effective.

Provided you have been issued with the Electrical Installation Certificate, 6 year warranty and building control have been notified so you get a compliance cert, then the job has most likely been done legally and properly.

Answered 12th Apr 2013

Electrical Safety Services

Member since 17 Oct 2011

They could of drilled through the joist at the right depth and position as per building regulations, they were being lazy.

Page 119 'Electricians guide to the building regs'

*Notches on top of joist in a zone 0.07 and 0.25 x joist span.
*Max depth of notch should be 0.125 x joist depth.
* Holes on centre line of joist in a zone between 0.25 and 0.4 x joist span.
* Maximum diameter of hole should be 0.25 x joist depth
You can take a feed from the existing lighting radial in he loft serving the lights on the first floor in your loft (it wont be a ring) and take it to a switch and then to the light in the loft.

hope this helps

Answered 12th Apr 2013

Mark Harris Electrical Services

Member since 21 Mar 2012

I have always been under the impression that clipping cables to the top of a joist in a loft does not comply with bs7671 or is certainly bad practice, as the cables will undoubtedly be damaged my people standing on them or boxes ect being stored on the cables.
I have always clipped cables in a loft to the side of the joists and if need to run across the joists I clip along a supporting beam or put my own piece of 2x2 to clip on the side of. Or if its just through a couple joists I will drill a small diameter hole.

Answered 15th Apr 2013

A T Electrical

Member since 29 Jun 2012

I would not allow any drilling into ceiling spars this would weaken them to a point where they become unsound, we are not talking floor joists here and if they are trussed rafters I think the manufacturer advises not to drill these members.

Answered 13th Apr 2013

chris tomlin

Member since 28 Mar 2012

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