Problem routing cables

[John]

Eventually going to rewire the whole house but for now we're doing the kitchen refurb and I'm doing some head-scratching regarding routing the new cables - this is in a 1971 semi-detached dormer bungalow.

The existing consumer unit is under the stairs on the other side of the kitchen wall (approx. central)

All existing cables exit the consumer unit through the back and I then expected them to go up to meet the slope of the stairs, along the incline upwards and into the ceiling void - but as you can see, they don't.

Instead, from

you'll see that they seem to be buried in the plaster (and under metal capping) following the angle of the slope. There's another photo as well at showing further detail.

I need to get 10 T&Es from (new) CU into the ceiling void (2 for kitchen ring, 2 for d/stairs ring, 2 for u/stairs ring, 1 for d/stairs lights, 1 for u/stairs lights, 1 for shower and 1 for smoke alarms) plus, of course, earth wires. Any ideas as to how I can route these cables properly and safely? BTW, I'm getting BCO involved re Part P so lets not get bogged down in a Part P debate :o)

John.

[Lobster]

If you look at this diagram

I think that means you can run cable within a zone 150mm away from any of the angles created by the sloped area and the wall (ie where they apparently go now); then run them vertically down the front of the wall where your writing is, directly behind the surface where your CU is. I think.

Out of interest - wouldn't the sloped area class as "ceiling" not "wall"? And if so, would it then be OK to run cable anywhere behind the sloped plasterboard or would the "not less than 50mm deep" rule apply there?

David

[John]

Hmm, I think you may be right there David. Perhaps I could run the new ones apparently where the existing ones are - any further clarification (or other ideas) anyone?

With regard to the sloped area being ceiling as opposed to wall - that's how I would consider it and, indeed, it's where I expected to see the existing cables and where I originally intended to run my new ones. The problem (as I see it) is where the slope meets the "real" ceiling - I can't see a way of drilling from top of slope into ceiling void because of the last stair riser etc.

Thanks for your efforts mate,

John.

[Andy Wade]

For the purpose of Reg. 522-06-06 I think the under-stairs slope would count as a "partition" - in which case you could follow the original route, provided that you can get all 10 cables into the 150 mm wide zone without the grouping factors becoming a problem. You really need all the cables in a single flat layer and spaced with a one cable's width gap between each pair of cables. (The fire alarm cable, and possibly some of the lighting, can be ignored because the design current will be less than 30% of the grouped rating.) This might be easier said than done.

Is it not possible for the ground floor power circuits to go down and along under the floors, as this would help a lot? Solid floors, I suppose...

If you follow your original route under the stairs, you could get through to above the ceiling if you built a box to effectively drop the ceiling level down by three or four inches before it meets the stair slope, IYSWIM. Remember that cables passing thro' joists, noggins and battens etc. above a ceiling must be > 50mm from the edge of the said timber member (not from the face of the plasterboard) [Reg. 522-06-05].

I suggest that it would be worth discussing this with building control - see if you can get to talk to whoever they'll use to do the inspection and testing, preferably on site. They will want to do a first-fix inspection in any case. By seeking their advice you'll avoid any conflict later on - and being to to re-do this bit when you thought you'd finished would be a disaster...

[John]

Hey Lobster - and anyone else who happens to be looking, of course - I've just had a few beers and spawned an idea that may work. Have a look at

Just got an odd piece of timber from the garage and clamped it onto the slope to see if "lowering" the slope would work IYSWIM.

It would give me enough room for the cables behind the plasterboard slope and then I could drill through the joist into the ceiling void. Probably not making any sense as I've just got back from the pub but hopefully the photo will explain for me. Any views anyone - will this comply with the regs?

I'm off to bed so I'll look for replies tomorrow. 'Night all :o)

John.

[Andy Wade]

That principle might work well, but I think you'd need to use 75x50 or

100x50 timbers rather that the 50x50, to lower the slope more. Then you could avoid drilling the joist altogether. Drilling the joist as you've shown looks potentially dangerous - especially as it will be a long row of holes. (See also my other reply.)

[John]

Ahh, thanks very much Andy. I didn't see your other reply last night although it was timed about an hour earlier than mine. I'll put it down to server lag as I can't have been that drunk :o) That's a brilliant idea though mate. Off to buy some 100x50 timber right now.

Cheers,

John.