slope for roof

[jaspercarrot]

i want to change my extension flat roof for a box profile steel sheet roof, i intend to use furrings to achieve the slope. my roof is 16 ft long,

what is the MINIMUM pitch required to do this.

thankyou.

[buildersmate]

One in 80 may be fine for a perfectly flat roof, but if you have any intention of using overlaps 1 in 60 may be better, to avoid any danger of water sitting on the thing.
If this is a garage or outbuilding (and hence non-habitable) and also less than 35 square metres in external floor area, Building Regs don't enter into it, so issues like proving the strength of the thing (Building Regs Part A which Zac kindly provided you with) or insulation aren't relevant. Though nevertheless there's nothing to stop you using such standards as guidelines.
Planning consent may be an issue so worth asking - particularly in view of the appearance of a box steel roof in the general area if it is a residential area.