Cables in cavity walls?

[driverman]

Hi, 2 things really but related. 1. When I worked for a DNO company, no way would they allow their service cable to the OMB go via the cavity even if a hockey stick was installed. Yet in the UK Power Network (old Eastern) area it would appear they do. Any one know from their experiences?
2. Ground worker at new build doing all the drains etc, installed a SWA cable (only, laid in ducting) for sewage septic tank pump. The thing is though, he has also installed a hockey stick up the cavity for his SWA cable. I will be connecting, testing the SWA cable. Tomorrow, I will informing home owner that the SWA cable CAN NOT remain in the cavity. Nor would I think the DNO will allow their cable to be in the cavity wall.
If Septic tank cable left in cavity, if allowed, would that be classed as a deviation on EIC? My thoughts are that it should not be there at all.
Thanks

 

[ImpededLoop]

If I were the home owner, I'd want to know why it can't remain as it is.

As long as the cable is suitably supported and hasn't been damaged during installation, I can't see what reason you can give to justify pulling it out and I suspect clipping it surface up the wall.

The DNO will have their own rules for their cable.

 

[Knobhead]

Who’s cable is it? It’s not the DNO’s so BS7671 applies.

Careful what you tell the customer because you’re liable to end up with egg on your face!

 

[davesparks]

And what regulation will you be using to back up this statement that the cable cannot be there?

 

[driverman]

Looks like I'm in the wrong here. I was generally under the impression that cables were no longer allowed in cavity wall.
Thanks for replies

 

[7029 dave]

In the hole for me.

 

[HandySparks]

Looks like I'm in the wrong here. I was generally under the impression that cables were no longer allowed in cavity wall.
Thanks for replies

I don't think that there's a regulation, as such, against cables in wall cavities but there are some factors such as thermal insulation (whether present at the time of installation or not) which would affect current carrying capacity. You might also consider the increased risk of cable damage due to the cable being concealed (even if deeper than 50mm) whereas a surface run cable is more likely to be noticed.

 

[Anthony S]

Might not be a electrical reg but in clear cavities they are kept clear for a reason, Water tracking from outer leaf to inner leaf. I suppose in soft filled cavities forcing a cable down the cavity it could bridge out the outer leaf and the inner leaf and water could track across.

Why do you think wall ties are shaped the way they are ? to allow any water coming down the cavity to drain to the outer leaf.

 

[HandySparks]

Certainly worth making sure that anything you poke through a cavity slopes downwards towards the outer leaf. With most small cables I use a piece of 20 or 25mm pvc conduit to make threading the cable through easier and keep it separated from any insulation (some polystyrene insulation can de-plasticise pvc cable).

 

[Engineer54]

Might not be a electrical reg but in clear cavities they are kept clear for a reason, Water tracking from outer leaf to inner leaf. I suppose in soft filled cavities forcing a cable down the cavity it could bridge out the outer leaf and the inner leaf and water could track across.

Why do you think wall ties are shaped the way they are ? to allow any water coming down the cavity to drain to the outer leaf.

That old chestnut again!!

So what about insulation filled cavities then, and the lumps of mortar left on 70% of all those cavity ties bridging the cavity during construction?? Did any of these cause internal damp in the past, ....Nope??

 

[andyelectric]

On new houses it is a fallacy as the outer skin is design to be weathertight. So for a modern house it is an old chestnut.

With some early cavity designs (late 1800's to early 1900's)where lime mortar is used there is a real problem if a cavity is bridged. The reason is the brick and mortar is designed as a breathable structure. In fact the early cavities were designed for coastal areas with driving rain where there were real problems with damp in solid walls.

 

[HandySparks]

On new houses it is a fallacy as the outer skin is design to be weathertight. So for a modern house it is an old chestnut.

It may be designed to be weathertight but the reality is different. I have seen rainwater dribbling down the inside of a modern south-facing single skin brick wall after a few days of heavy rain and wind. Maybe it was a poor mortar mix, but it happens.

 

[Engineer54]

On new houses it is a fallacy as the outer skin is design to be weathertight. So for a modern house it is an old chestnut.

With some early cavity designs (late 1800's to early 1900's)where lime mortar is used there is a real problem if a cavity is bridged. The reason is the brick and mortar is designed as a breathable structure. In fact the early cavities were designed for coastal areas with driving rain where there were real problems with damp in solid walls.

You have far more chance of mortar bridging a cavity than a cable. Most damp in cavity walls are caused by failed old mortar that is in dire need of repointing, and/or water ingress through exposed holes, that haven't been made good after whatever went into or through the wall was removed....

 

[andyelectric]

You have far more chance of mortar bridging a cavity than a cable. Most damp in cavity walls are caused by failed old mortar that is in dire need of repointing, and/or water ingress through exposed holes, that haven't been made good after whatever went into or through the wall was removed....

I agree with modern walls it would be holes etc that would be the source of any problem.

And I also am well aware that a cable bridging a cavity is in all likelihood not going to cause damp.

I am just saying that with older construction there is that chance and it is not an old chestnut in this particular scenario. Not much is taught nowadays about older buildings, it is a nightmare to get a builder properly conversant with lime.

I'm not really trying to cause an argument, just pointing out it is not hard and fast.