On Tue, 7 Sep 2004 11:54:01 +0100, a particular chimpanzee named
"Pecanfan" randomly hit the keyboard and produced:

"1.21 Stairs designed in accordance with BS5395 Stairs, Ladders and
Walkways. Part 2: 1984 Code of Practice for the design of helical and spiral
stairs, will be adequate."

Where do I get BS5395? Does BS5395 specify the same stuff shown in Building
Regs Doc K or does it have some extra stuff?

BS 5395: Pt 2 relates specifically to spiral stairs. There is a _lot_
of extra stuff, including some complex calculations. BS aren't
downloadable, or at least not for free.

"Stairs with goings less than shown in this standard may be considered in
conversion work when space is limited and the stair does not serve more than
one habitable room."

What does it mean by 'this standard'? Does it mean the standards in Doc K
or the standards in BS5395? ...and what does it mean by 'one habitable
room'?

It means BS 5395: Part 2. The minimum widths in the BS can be reduced
in loft conversions where there is only one room accessed by the
stair.

...and if I can get away with a spiral staircase, why on earth aren't I
allowed a 45 degree straight staircase with say, 250mm rise?

Because a properly designed spiral stair is perfectly safe. The
maximum rise on a spiral stair is 220mm, and the natural inclination
is to walk on the outside of the tread which is wider than the minimum
for a straight flight.
--
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?"'