TheScullster wrote:
Never heard of box profile steel roofs!

The modern equivalent of corrugated iron. Think any big
warehouse - e.g. B&Q or whatever - the roof will almost always
be box profile.

It's thin (0.6-0.8mm) galvanised steel that's polyester coated.
Comes in many colours.

Can we fit one on single storey extension in lieu of flat roof or are they
just for garages?

Well, I think in terms of functionality and building regs, yes
you can (with adequate insulation). But aesthetically - garages
and warehouses only IMO.

--
Grunff