Cable routing again

[onzadog]

My exterior walls are the common plaster on breeze block, then a void and then brickwork exterior. My question is, do I have to recess into the plaster or can I go through the breeze block, up the void and back through the breeze block in the loft? I know it sounds like more work but I really hate decorating!

Any comments folks?

Thanks

 

[festa]

No you cant run a cable in between the cavity of the walls as any damp that DOES come through the exterior brickwork/mortar will use the cable to bridge to the interior wall.

 

[onzadog]

Thanks for the reply. I'm always willing to learn about such things. I can understand how this might happen but how come the same doesn't happen with the foam that's filling the cavity?

Isn't running a cable in the void the same method as the cables use to get from the consumer unit to the various parts of the house?

Like I say, the reason I'm asking is because I don't know.

Thanks for the help.

 

[festa]

Not too sure what the foam is made of but its a formula that damp cannot affect i suppose...good question and an answer im not sure on .

As for cables going to and from a consumer unit again they `should not` be run in cavities, they should be run surface mounted to floor/ceiling voids or can be run in conduits screwed to the plaster /inner brick face.

Some new builds ive been learning on recently have sited the consumer units at around 1200mm high on an interior wall and run lengths of 200mm x 50mm trunking at a corner of the house from ground floor to ceiling and 1st floor to roof void,all in one particular corner of the house.

 

[onzadog]

On closer inspection, the cable to the consumer unit passes through the block, void and brick to the unit in the porch. I guess this is where a little common sense is applied as there's no real alternative. The unit is at such a height that some go off through the floor space between levels and the others I've found fun up trunking/conduit inside the plaster in the corner of the building (guess that's the 150 mm permissible zone).

Looks like I need to start chipping away at the plaster and thinking about redecorating then!

Pants!

Thanks for your help though.

BTW, how many lengths of 2.5mm T&E can you normally fit it plaster recessed trunking?

Thanks again.

 

[securespark]

If you've got insulation in the cavity there are two reasons at least why you should not run cables in there.

One: the insulation will cause the cable to warm up, as it cannot dissipate heat as well.

Two: some insulations damage the pvc: they leech the plasticisers out of the pvc, causing the insulation to become hard & brittle.

 

[ssray]

The foam wil be closed cell so will not allow the ingress of water, a bath sponge will be open cell so it asborbs water.
Ray
If onlt ohms law etc was as easy!!!