Cables and cavity walls

[Spoon]

Nitro Pro 10 is just what we have at work so I use it. Seems good.

 

[Midwest]

Nope, it was autocorrect.

Pheeww, thank God for that.

 

[Spoon]

I have Adobe Acrobat.
Just seems a bit clunky.

If you are having problems with a PDF then I can OCR it with Nitro, if you want. See if its better..

 

[driverman]

Cables in external cavity walls are not allowed. Another reason why not, is that a 3rd party might hit them when drilling through wall to install TV cables etc

 

[westward10]

And they wouldn't hit them if they were chased instead?

 

[Spoon]

Cables in external cavity walls are not allowed. Another reason why not, is that a 3rd party might hit them when drilling through wall to install TV cables etc

Can you give a reg number for that mate?
Would someone drill through the full width of a brick (102mm) to fix a TV cable?

 

[Midwest]

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.

 

[ukiri]

And they wouldn't hit them if they were chased instead?

That's what zones of protection are for

 

[Deleted member 26818]

That's what zones of protection are for

Prescribed routes.
You don’t think there would be a prescribed route if the cable were in the cavity?
You should also consider what happens to loose cables when drilled as opposed to captive cables.

 

[Midwest]

Thats that then. New builds should have all the cables run in the cavity, wouldn't have to worry about sheathing or clipping the cables.

 

[Deleted member 26818]

Thats that then. New builds should have all the cables run in the cavity, wouldn't have to worry about sheathing or clipping the cables.

Ahh, Irony, nice.
Just a little more subtle than sarcasm.

 

[Midwest]

Someone's tired.

 

[Deleted member 26818]

 

[pirate]

Irony?
Hmm...don't think I'll be phoning Alanis any time soon...

 

[Deleted member 26818]

Irony?
Hmm...don't think I'll be phoning Alanis any time soon...

I think the irony is that none of the things she quotes in her song are ironic?

 

[pirate]

Indeed, they are just unfortunate...which is ironic in a song supposedly about irony...
good song though, ironically

 

[telectrix]

more like moronic.

 

[driverman]

Can you give a reg number for that mate?
Would someone drill through the full width of a brick (102mm) to fix a TV cable?

Re drilling through cavity walls. Was just an example. Many Sky installers drill straight through cavity walls. Gas plumbers also.
Cavity wall installers installers drill into the cavity.
As for Reg No., no, I don't know. But correct me if I'm wrong, has not installing cable within external cavities been banned for years?

 

[DPG]

Don't think it's been banned, but it's definitely not a good thing to do for the reasons given before, ie. bridging the gap, and lack of support for cables (more of a problem with horizontal runs than vertical admitedly). Cavity wall ties also bridge the gap, yes, but they are designed with a drip loop so that the water drops down before meeting the inner leaf of the wall.

 

[pirate]

Unless you are wiring in the cavity in a school in Scotland, funded by PFI...they just didn't put the ties in, so no worries about fouling them, just drill and install your cables...
fkwts!

 

[Spoon]

As for Reg No., no, I don't know. But correct me if I'm wrong, has not installing cable within external cavities been banned for years?

There’s no prohibition in BS7671 against running cables in cavities.
In fact BS8436 cable is designed for use in building voids and BS7671 lists installation methods 40 to 44 as being writhing building voids.

Isn't the cavity a building void?

 

[DPG]

View attachment 44191

Isn't the cavity a building void?

Even if it is, it's governed by building regs/good practice which preclude bridging the gap.

 

[Spoon]

Even if it is, it's governed by building regs/good practice which preclude bridging the gap.

Everyone knows its bad to bridge the gap, so that water can transfer from the outside wall to the inside wall but it is possible to put a cable in without doing so.

 

[DPG]

It is in some cases yes.

 

[driverman]

View attachment 44191

Isn't the cavity a building void?

Interesting, I wouldn't class an external cavity wall as a void myself. Cables can not be supported in cavity walls. Insulation also cavities.
OK, do electricians still install cables within cavity walls?
I also thought that even PVC/PVC tails between the OMB and consumer unit could not be installed in the cavity. Contractors in my area would use metal sheathing to cover the tails before plastering.

 

[Spoon]

Cables can not be supported in cavity walls.

As I have stated in my post #15, the OSG suggests a max length of 5 meters between vertical cables. The BBB doesn't give any actual length.
Is it good practice? That may be down to the electrician.
If doing so then they would have to take any insulation,if installed, into account and size the cable accordingly.

 

[dksanders]

And they wouldn't hit them if they were chased instead?

but if they were chased they'd be accessible to repair, in the cavity they aren't

 

[Wilko]

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

 

[telectrix]

if the cable entry hole in the outer skin is properly sealed how can water penetrate into the cavity?

 

[Spoon]

if the cable entry hole in the outer skin is properly sealed how can water penetrate into the cavity?

Bricks are not waterproof mate.