My home is a semi detached chalet bungalow originally built in 1956. The
upper storey was created some 25 years ago by adding a back flat roof
conversion to a previous semi- detached bungalow. The main bathroom is
downstairs on the (front) north east corner of the building and the mains
electrical panel is in a kitchen pantry at the south east corner of the
building. The switch panel is a recent Wylex unit with spare slots. Upstairs
bathroom provision consists of a cloakroom with a toilet and wash handbasin.

We are completely refitting the main bathroom and as part of this plan to
have a 10.5 kw electric shower fitted as our aging central heating boiler is
a backboiler and we wish to keep all options open (including a combination
boiler) when we consider replacement in due course. Given that the upstairs
flooring consists of 8x4 foot chipboard sheets we are daunted by the
disruption which is likely to arise from the exercise of taking a new power
supply from the switch panel to the bathroom. We realise that the cabling
required for a 10.5kw shower is thick and inflexible but would like to use a
high rated shower in order to enjoy good performance. Looking at the
possible options:-

1. Would it be legal / practical to take the wiring along the outside of the
building in conduit - this would appear to be a straightforward run of some
25 feet. The wall involved is adjacent to the (concrete) driveway and is
covered for the majority of the length by a carport? Would we be likely to
encounter problems in bending the cable sufficiently to cope with the angles
involved?
2. If the above is not an approved approach and we do have to cope with the
disruption upstairs - what would be the easiest way of gaining access
through the floor? The chipboard (19mm) lays on 38mmx225mm joists which run
at right angles to the direction in which the cable has to be taken. The
original downstairs ceiling joists run in the direction the cable has to
take.
3. Any other ideas?

Any help gratefully accepted.