Ladies and gentleman can you help please. Need to build a new roof with corregated bitumin panels (wicks) for my workshop. Span unsurpported is 5,20m (17') by 16'4". Want to use a 15 degree pitch ( planning regs says 12 and i wont need permission). No span tables for this shallow pitch as far as i know : . Walls are sectional concret. If I can manufacture trusses from wood, what size will I require? Am thinking of doing them in steel. I am at your mercy