Wall Cavity Wiring.

Street light columns used to have a long length of 1.5mm2 T&E run from head to bottom with no internal supports for the cable with no problems. Surely 2 or 3 meters for a cable drop in a cavity won't strain it?

Depends how it's supported at the top. I think the general rule of thumb is that drops of up to 5m can be self supporting - but you do need a good (usually rounded) support at the top. Being bent around the top edge of a (possibly cut or drilled) brick probably isn't quite as good in that respect.

Vertically run cables in a cavity may not bridge the cavity. Wall ties do.

Wall ties are specifically designed to 'drip' in middle of the cavity - so they can't bridge water from the outer leaf to the inner one (at least if they're properly installed and aren't covered with mortar snots) - unless you can be 100% sure you cable can't touch the outer leaf and then the inner one on its way down it could form very effective bridge to carry water into the house.


  - Andy.

Street light columns used to have a long length of 1.5mm2 T&E run from head to bottom with no internal supports for the cable with no problems. Surely 2 or 3 meters for a cable drop in a cavity won't strain it?

Depends how it's supported at the top. I think the general rule of thumb is that drops of up to 5m can be self supporting - but you do need a good (usually rounded) support at the top. Being bent around the top edge of a (possibly cut or drilled) brick probably isn't quite as good in that respect.

Vertically run cables in a cavity may not bridge the cavity. Wall ties do.

Wall ties are specifically designed to 'drip' in middle of the cavity - so they can't bridge water from the outer leaf to the inner one (at least if they're properly installed and aren't covered with mortar snots) - unless you can be 100% sure you cable can't touch the outer leaf and then the inner one on its way down it could form very effective bridge to carry water into the house.


  - Andy.