GMM wrote:
Well well well....If I'd known it was going to cause such controversy
I would have thought of a different way to ask the question!!

Let everyone be assured that the house won't fall down because it has
a straight floor and by the time I'm finished it will be stronger than
it was to start with. That, of course, wasn't the question: I was
simply after some suggestions for how I might do a decent job of
cutting the top straight!

I might have to do some off site experiments and see what 'feels' best
between Jim K's power plane, Ghostrecon's router and dennis's guided
saw, though I suspect that whatever I use will be a bit of a bugger
all the way along a joist. I would replace it as suggested but that
would mean I'd have to rewire half the house as pretty much every
cable in the house goes through this joist.

Cheers people

You're welcome GMM.

If you go ahead and decide to cut the joist, have you thought of using a
very sharp axe, cutting with the grain to 'knock' most of the waste off -
and then finish off to the correct height using the electric planer or even
a sharp hand plane?

Just to perhaps cause a little more controversy with one or two here - if
you could get hold of an old adze, that would be even better, as you could
stand up and do the job, and with a sharp tool and a little bit of practice,
get an almost plane-like finish for a lot-less effort.

Just wear a pair of steel toecapped shoes and shin-pads though while you're
learning. :-)

All the best with a bugger of a job, and let us know how you get on.

Cash