Cables in Cavitys

[daza1001]

Hello all,

Are cables allowed to be run in cavity walls?
I say they are not, but a work mate says they are. What problems & regs relate to this?

Many thanks

 

[telectrix]

cables unsupported and liable to get chafed. reaction with the pvc and the cavity wall insulation. you're right. he's wrong.

 

[daza1001]

Thought so, thanks.

 

[Hawca]

just to back this up, when teaching it was pointed out you cannot do this for a number of reason..

undue stress on a the cable hanging (hence must be supported)
where a cable touches an outside wall damp patches will occur
thermal insulation and cable heat / resistivity

to name a few

 

[JamesBrownLive]

Interestingly enough, Alan Lynch, in his book 'The Part P Doctor' argues that this is perfectly acceptable..

He states that p111 of the OSG states that an unsupported drop of 5m is allowed. He says the argument against water transfer is bogus because the wall is filled with cavity wall ties that bridge the gap anyway. He does however, state that insulation is a problem although more to do with derating of the cable than of polymer migration from the PVC.

He goes further and debunks quite a few, according to him, myths.
Its certainly an interesting read, for which he received an industry award. I don't think they would be handing those out if his book contained a lot of BS. It would be nice though to hear what the older more experienced forum members think of what he has to say...

Personally, I'm still wet behind the ears :yes:

 

[claret73]

I have been on a new build and the Meter Box is sited outside the garage on each house. The CU is 2-3 metres into the garage on the internal wall. I asked the Spark if this was allowed to run through the cavity to the meter box. He checked with NICEIC & they said Yes!...Interesting to watch the alarm guy there the other day drilling through installing a cable from the panel to the Control panel by the front door...

 

[Deleted member 26818]

There's no Regulation in BS7671 prohibiting the installation of cables in cavities or building voids.
There are Regulations that by doing such, may not be complied with, and there are other considerations that will require consideration.
Ther are many instances where cavities are bridged, wall ties, windows, doors, incomming services, etc.

 

[swc]

There's no Regulation in BS7671 prohibiting the installation of cables in cavities or building voids.
There are Regulations that by doing such, may not be complied with, and there are other considerations that will require consideration.
Ther are many instances where cavities are bridged, wall ties, windows, doors, incomming services, etc.

Could you elaborate on that answer since in our house there's twin and earth in the cavity which has insulation in it. We are about to have a new cu put in since we've put up a two story extension and little summer house type thing in the back garden.