In article ,
"Simon" writes:
Hello -

A relative has a small outbuilding that needs a general overhaul of its
electrical wiring, and I'm wondering if it could be DIY'd without coming
under Part P.

No. All such wiring comes under Part P.
It's a separate question if you can self-certify or not though.

It's basically a small steel-framed barn that houses a couple of cars and a
couple of horses. There's no wiring in the horses' part. It's fed by a short
buried cable from the consumer unit in the house, which feeds a smaller
consumer unit in the barn. Things which need to be addressed include:
- Most of the sockets and switches are old, some are cracked. Some may be
exposed to rain during severe weather.
- A family of swifts has built a nest on top of the barn's consumer unit,
which needs to be replaced.
- Presumably the earthing requirements need to be looked at, particularly in
view of the amount of earthed steel around.

This is a very important issue, much more so because of the
horses. Tiny leakage currents which humans can barely feel
are fatal to most livestock including horses, so this has
to be got right. For this reason I strongly suggest you get
the work done by an electrician who is familiar with supplies
around farm livestock. There are issues here which domestic
electricians are unlikely to be very familiar with.

--
Andrew Gabriel