"Christian McArdle" wrote in message
et...
A quick play with SuperBeam appears to indicates for my proposed loft
conversion floor (4m span, 2kN/m2, 500mm spacing), I need either:

1. Timber joists (220 x 50) (CL16)
2. Flitch joists (147 x 50) (10mm plate, not full depth)
3. Steel joists (127 x 76). (UB 13mm thickness Grade 43)

Given that the steel joists would save 70mm of height, propelling the
project into feasibility, why aren't all loft conversions done with
them?
Furthermore, the calculated deflection ended up as 3.4mm rather than
11mm,
so it would be less bouncy.

A quick phone up of the local steel merchants gave me the chance to
sound
all professional by reeling off the SuperBeam specifications (they
seemed to
know what I was saying!) and gave me a total cost of around 700 quid
plus
VAT to joist out a 8m by 4m total area, making the cost only a small
proportion of a loft conversion anyway. It's not like the timber would
have
been free, either.

Is there something preventing the use of steel for joists? I realise
that
they need to be fireproofed, but this can't be that expensive can it?
Isn't
the fireproofing just squirty foam?


you also have to allow for a method of attaching the flooring to the
steel

when I looked into this for my loft I found the best method of saving
the most headroom was to span steel beams with wood inserts across the
longest length, and suspend wooden joist from them