On Sep 20, 8:32*pm, Harry Bloomfield
wrote:

An L shaped about 7mm thick solid plastic is used for the vertical,
this is simply nailed onto the face of the beam using plastic capped
stainless steel nails specially made for the job. Our timber ends

Those are capping boards, designed to be fitted over existing wooden
fascias.

Stand-alone fascias are thicker (2x at least).

See http://www.eurocell.co.uk/buildingpl...assoffits.html

Ventilation is supposed to be provided in the horizontal surface,

The term is "soffit" and, IMHO, it's a lot easier to buy soffit boards
with a continuous vent strip built in, than to faff about fitting
separate vents. I'm surprised your man didn't appraise you of this.

MBQ