Thanks for ther TRADA link, it makes good reading.

http://www.luton.gov.uk/Media%20Libr...r%20floors.pdf

There are a few constraint in what I am doing :

1) I dont have access to the underside of the joists, beacause I have a
ceiling there already, which rules out the metal straps
2) The new joists are going on on 400mm centres between the 600mm centred
trusses, which means 2 out of three of the gaps will have a
3) The regs say that noggins need to be 3/4 of the depth of the joist

I am fitting 9" joists, which means i'd need 6.75" noggins. However, a 6"
noggin would almost be resting on the tops of the truss joists, which means
I cant use to-the-spec noggins, and the metal straps are basically out of
the question...

Now, given that I dont plan to live in my loft i'm only flooring for
storage, and that i'm not after BCO approval, and by the sound of it some
people in older houses have hardly any strutting anyway, can anyone venture
a guess at what I would safely get away with, regardless of BCO regs etc?
For instance, if I used 100mm noggins and 22mm T7G floorboards, would that
be good enough to use occassionally and store, even though it wouldnt meet
the regs?

Cheers
Chris