As far as the OP is concerned, if he *hasn't* gone to the trouble of
actually attaching the cable to one or other leaf of the cavity and if
he is intending to fill the cavity with loose insulation such that the
cable will be completely surrounded then yes, he probably does need to
rethink, and the idea of a 20A "ring" although non-standard is
possible. If, on the other hand, he *has* attached the cable to one of
the leafs (leaves?) or is intending to use solid batts of insulation
which will ensure that the cable is pushed up against a leaf then he
can probably rest, safe in the knowledge that he can plug three 3kW
heaters into his ring and not run the risk of melting his UPVC.

HTH

Hwyl!

M.

I had precisely the same issue as the OP, viz. dwarf cavity walls and
wanting not to use plaster on the inside but to have brick.

I wanted to run a power ring circuit and also CAT5, CT100 and speaker
cables.

Clipping the power cables within the cavity to a leaf using convention
clips was not practical, so I devised a way to do this differently. I
also had in mind the rules about cables needing to be in a band of
150mm down from the top of a wall and at least 50 mm below a surface.

So, I began by fitting insulating batts up to a distance of about
250mm below the top level of the wall. I ran all of the non power
cables simply by laying them on the batts at this level and feeding
through. I then added strips of batt to take the insulation up to a
level 100mm below the top level of the wall.

I made special brackets from fairly stout galvanised strip about 8mm
wide and fashioned towards one end a U-shape designed to accept the
power cable. The other was bent to an L-shape, but actually slightly
acute of the 90 degree angle. The distance from the U part to this
bend was about 60mm, as was the remaining straight piece the other
side of the L. I covered the U part in two layers of heat shrink
sleeve and drilled a hole 25mm from the other end.

At each clipping position I had had the builder put in wooden blocks
between the bricks to a depth down from the top of 15mm, and coming
forward from the cavity side of the inner leaf by 50mm. Mortar was
placed in front of these blocks so that the inside face of the inner
leaf is normal. The same thing could have been done after building
by carefully drilling down from the top and removing mortar.

Each clip was installed by putting it into place holding the cable,
and temporarily holding with a clamp. Then the fixing hole position
was marked from above. The assembly was removed and the hole
drilled from above to receive a plug. The bracket was then refitted
with the cable, clamping again while the screw was inserted.

The effect is that the cable is held in place against the inner leaf
of the wall about 70mm down. I forget how frequently the clips were
placed, but within the horizontal clipping distance.

The space in the top of 100mm was left without any insulating batt.

So in effect, the cable is clipped to a masonry surface and is at
least 50mm away from any potential mechanical damage.





..andy

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