On 12 Oct 2004 09:51:41 -0700, a particular chimpanzee named
(StealthUK) randomly hit the keyboard and produced:

It's the first I've heard about burying cables 50mm. How many builders
or electricians do you think have complied with these regulations?
You'd be chasing half the brick wall out and that's not going to be
easy without some heavy duty machinery and surely would compromise
strength in the wall?

Vertical chases up to 1/3rd of the leaf thickness are allowed (33mm
for a 100mm block) but horizontal ones no more than 1/6th. Given that
most walls will have a reasonable thickness of render & skim over
(probably 13-15mm) or plasterboard on dabs (9.5mm + 10mm gap), then
the actual chase into the masonry should only be of the order of
30-35mm. So any cable should only be in a vertical chase.
--
Hugo Nebula
'What you have to ask yourself is, "if no-one on the internet wants
a piece of this, just how far from the pack have you strayed?"'