Existing attic cabling: re-routing, extending, etc.

[smp50]

Hi. The wiring for my upstairs lighting is currently routed very poorly through the attic and just lies across the various beams, coming in and out of insulation like a sea serpent.
I want to board the whole area out (standard rough floor) so have to get them tucked away somewhere. The wiring is quite old, I think, but I don't know when it was done. All the light switches are 30-40 years old, anyway. The cable is all t&e, old colours.

I can provide a diagram later but, for now:

> cable first appears in a corner of the attic floor
> passes to landing light and switch
> passes to front bedroom light and switch
> passes to back bedroom light and switch

All are looped in at the ceiling roses.

EDIT see below for diagrams! //www.diynot.com/forums/electr...ling-re-routing-extending-etc.350863/#2635685

I'm going to install an attic light from the last ceiling rose in the series, and this cable I will route entirely around the outside permiter of the attic where the boards won't reach to anyway. This seems like the sensible way to do it.

To get the existing cables out of the way, it seems like I have several options:

1) Notch the beams - not recommended?

2) Put new beams atop the current ones, raising the floor level but giving plenty of places for the cables to pass through everything.

3) Drill the beams - but if I was going to do this I'd need to take all the wire out of the ceiling roses to thread it through the new holes, and so while doing all that I might as well just...

...4) re-wire the whole thing to skirt the edge of the attic and get them out of the way (plus making them easier to access later).

I'd rather avoid it, though - seems like a waste of time, money and cable.

If I did go ahead, some further points to consider:

a) the current cable in place isn't nearly long enough to run around the permiter of the attic floor. Would I need to install all-new cable or can I extend what's already there by joining end-to-end with new cables (in some kind of junction box?)

b) related to that, to avoid pulling up the cable that comes up from the floor below, and also the cables down to switches, I'd rather leave those pieces as they are. In that case, in the attic there would be a mixture of old and new cables - is that OK?


Thanks,

 

[ricicle]

1) Notch the beams - not recommended?

NO!

Drill the beams

NO!


Options 2 or 4 are the best way forward.

 

[PrenticeBoyofDerry]

1) Notch the beams - not recommended?

What depth are the beams/joists?, although notching is not the best solution, it would depend on joist depth, span of supporting walls and additional protection whether that be mechanical or addition of to joist depth. It is not strictly a no no.

2) Put new beams atop the current ones, raising the floor level but giving plenty of places for the cables to pass through everything.

Again I will refer to the above, regarding structural quality of existing joist.

3) Drill the beams - but if I was going to do this I'd need to take all the wire out of the ceiling roses to thread it through the new holes, and so while doing all that I might as well just...

Again holing the joist is not a no no, but depth of joist and spans are agian to be considered.

...4) re-wire the whole thing to skirt the edge of the attic and get them out of the way (plus making them easier to access later).

An option, but if routed correctly with no joints, access would not really be required unless mechanical damage was made to cable, which routing correctly should help prevent,

a) the current cable in place isn't nearly long enough to run around the permiter of the attic floor. Would I need to install all-new cable or can I extend what's already there by joining end-to-end with new cables (in some kind of junction box?)

Any junction would require to be easily accessible, unless the use of MF junction were used but jointing is best avoided, if possible

b) related to that, to avoid pulling up the cable that comes up from the floor below, and also the cables down to switches, I'd rather leave those pieces as they are. In that case, in the attic there would be a mixture of old and new cables - is that OK?

it is okay but there shoulds be a warning/notice placed at the fuse board, stating that two Versions of BS7671 wiring colours are present.

Untitled

• PrenticeBoyofDerry
• 14 Oct 2011
• 4

 

[sparkwright]

If you're not prepared to re-wire the lighting, you could consider fixing some battens to the tops of the joists, leaving gaps for the cables. Then board over the lot.

You should use metal nail guards over the cables, as there is a strong possibility of the cable getting nailed through.

 

[smp50]

Thanks for the replies. I've prepared some generalised plans to show you guys the situation:

1) Basic attic floor plan. The attic space does extend beyond the boundaries shown but the floor kind of dips down a bit there, it's hard to describe.

http://i.imgur.com/XaDpx.png

2) What's underneath.

http://i.imgur.com/kEfzP.png

3) Current cable layouts. Origin is in the top right, final light and switch are on the left. The first ceiling rose on the circuit (i.e. in the middle of the diagram) is part of a two-way switching setup, hence the single cable, I suppose.

http://i.imgur.com/Ige9k.png

4) Proposed new cable layout. Roughly 40m required.

http://i.imgur.com/UqRlg.png


What do you reckon?

 

[PrenticeBoyofDerry]

Have you any structural walls beneath the existing joists?
As by what I can make out, your existing joist span is 5.75m and are only 3.5 inch X 2 inch, then you are going load 6X2s plus floor panels and stored goods. But no detail of any supporting walls for this span.

 

[smp50]

Have you any structural walls beneath the existing joists?
As by what I can make out, your existing joist span is 4.5m and are only 3.5 inch X 2 inch, then you are going load 6X2s plus floor panels and stored goods. But no detail of any supporting walls for this span.

Good point - I'll add in the walls, there is a solid wall (I presume load bearing) half way along.

 

[smp50]

Have you any structural walls beneath the existing joists?
As by what I can make out, your existing joist span is 4.5m and are only 3.5 inch X 2 inch, then you are going load 6X2s plus floor panels and stored goods. But no detail of any supporting walls for this span.

Walls below now detailed:

http://i.imgur.com/XaDpx.png

The house is a 1935 ex-LA end-of-terrace and all seem to be solid internal walls.

 

[smp50]

Any final opinions before I go ahead with this?

 

[PrenticeBoyofDerry]

Should be okay for lightweight storage, if you could use joist hangers on the 6"X 2"s should also offer additional support.
You will reqiure more than two 6 x 2 though, they should be spaced at about 400mm centres, to support the floor panels.

 

[smp50]

Should be okay for lightweight storage, if you could use joist hangers on the 6"X 2"s should also offer additional support.

To fix the boards to the 6 x 2's, right?

Good idea, thanks.