Cables and cavity walls

[Deleted member 26818]

Hi - I think both can be repaired. I could pull a new cable through a building void pdq if required .

Damn sight quicker than chasing out the old cable, replacing it, filling and decorating.
Yes bricks are porous which is the point of having the cavity.

 

[telectrix]

so why do builders then bridge the cavity with itchy-poo?

 

[Deleted member 26818]

so why do builders then bridge the cavity with itchy-poo?

I assume the insulation is, or should be non-porous?

 

[telectrix]

it's about as non-porous as weetabix.

 

[Malcolm]

This thread reminds me, my son is an apprentice plumber on new builds. He asked me what are the regulations for cables in cavity walls?. He asked because the guy he is working with core drilled through the wall for the sink waste in the kitchen he also went through the tails to the cu. (Twice).
When I queried him it turns out if you can imagine looking at the front of the outside of the kitchen, the meter box and cut out are on the left of the kitchen window the tails go into the cavity turns right goes horizontally in the cavity under the window then goes into an internal stud wall and vertically up to the cu. If whoever installed the mains had put it to the right of the window he would not have gone through the tails.

 

[pirate]

Cavity wall insulation is not a good thing, imho. Anything that bridges the gap is likely to add to internal damp problems. If the insulation is porous it soaks up water, if it isn't, it can transfer water from the external leaf to the internal leaf. If you have a sealed external leaf, maybe it's ok, but that's uncommon. So many folks have been tricked into CWI by government initiatives where unscrupulouds traders persuade folk, especially the elderly, to let them drill holes in their walls...
I have a flat which was just fine and dandy until the CWI was installed, and the damp and mould were almost instant, albeit it was a very cold and wet winter...
The roof was also a problem, but the water ingress from there simply hit the CWI and travelled into the inner leaf.
Crap! I just had an EPC done on my house which said CWI would cost £500 and save me £27/year over 3 years, and if I installed PV panels at about £8k I could save £327/annum...those are govt figures, as the EPC guy simply downloads them...so, would I spend £8k for that saving? No...I'd turn off some lights.

 

[ukiri]

Found from an old IET thread
"Guidance from the Electricity Safety Council says "installing such cables in this way (external cavity walls) is generally an undesirable practice"

The reasons give are
1. Obstructions in a cavity wall, such create a risk of unseen damage during installation.
2. Long unsupported vertical drops may place undue strain on the conductors, leading to damage
3. Polystyrene used for insulation, if it come into contact with thermoplastic (pvc) cable sheathing, plasticiser can migrate from the thermoplastic to the polystyrene
4. Thermal insulation in the cavity may cause cable not to be able to carry the load current without overheating due to their current-carrying capacity being reduced
5. Presence of flora and fauna - unforeseen external influences

There is also a requirement in the Building Regulations 2000, Approved Document C, 2004 Edition, Section 5: Walls, paragraph 5.13 b
and NHBC Standards state that no cables other than electricity meter tails are to be located in the cavity of an external wall"

 

[diyterry]

I doubt if you could find a BS7671 reg or Building Reg against it. But if its at all possible, a cavity is not the place for any cable, unless its straight through or less than a couple of meters, aka meter tails etc.

The house I'am doing up has cables running up and down in the cavity.

 

[DPG]

The house I'am doing up has cables running up and down in the cavity.

Not ideal at all. If house is having work done then now is the time to get cables routed correctly.

 

[Midwest]

About 2m, no insulation in the cavity.

The house I'am doing up has cables running up and down in the cavity.

Have you found some more?

 

[diyterry]

I've got the floor up in the bathroom and I can see the cables for the RFC ( hope I've got that right ) and cooker disappearing through the wall into the cavity.

Have you found some more?

 

[Midwest]

Would this be just above the consumer unit (fuse board)?

 

[diyterry]

Would this be just above the consumer unit (fuse board)?

No the consumer unit is on the same wall about three yards in the opposite direction. There's a double socket in the kitchen, below where the cables disappeared into the cavity. The cookers further along on the same wall.

 

[Midwest]

No the consumer unit is on the same wall about three yards in the opposite direction. There's a double socket in the kitchen, below where the cables disappeared into the cavity. The cookers further along on the same wall.

It could be the way the cables have been routed into your CU, i.e. via the cavity. There's probably thousands of properties wired in this way in the past. As others have said, not against any regs etc, just not good practise in my & others opinion. But I suspect its been like this for some time, to no avail. You would need to employ a competent electrician and seek he/she's opinion.

 

[diyterry]

It could be the way the cables have been routed into your CU, i.e. via the cavity. There's probably thousands of properties wired in this way in the past. As others have said, not against any regs etc, just not good practise in my & others opinion. But I suspect its been like this for some time, to no avail. You would need to employ a competent electrician and seek he/she's opinion.

Before we bought the house we had the wiring surveyed by an electrician and he couldn't find any major problems.