Hi,

My roof trusses are made from 3" x 2" and there is a 4.5m span between the
wallplates, with just one internal tie from the apex to the mid point of the
joist. It all looks so flimsy that I'm quite nervous about storing anything
up there.

I had originall toyed with the idea of putting proper floor joists in so
that I can use it for storage, and then should I wish to do a full loft
conversion at a later date, the floor would already be up to the job. For
various reasons, I am moving away from that idea, but would still like to
beef up the floor by putting joists in raised a little further off the
wallplate for clearance.

Anyway, I;ve done all the calcs, and to satisfy the regs, over a span of
4.5m I'll need to use 2.5" x 9" on a 600mm pitch, or 2" x 8" on a 450mm
pitch for this floor to be upto loft conversion standard. Thats a lot of
expensive wood, and as I'll now only be using it for storage (admittedly
there will be books, and some heavyish stuff), how would I quantify the
risks of putting in 2" x 6" on a 450mm pitch, for instance. It is clearly
not up to everyday domestic use, but i am guessing that it will be sturdier
and a better solution thatn just laying boards on the 3" x 2" trusses. What
I can't grasp is the effect of the tie in the truss that runs verttically
from the apex to the centre of the horzontal. Does this effectively halve
the span of joist? If so, is 3" x 2" over 2.25m any better/worse than 2" x
6" over 4.5m.

In anycase, not laying boards on the trusses appeals as I am less likely to
crack the ceiling below while walking around, moving boxes etc.

Any thoughts?

Cheers

Chris