We don't generally provide design data for specific projects because of the possibility of not fully understanding all details of the proposed structure. Our preference is to refer inquirers to the span tables and design software available on our website here: https://www.woodsolutions.com.au/articles/span-tables-and-software. Since yours is a simple structure we can tell you that MGP10 grade pine could span 4.0 m, spaced at 1200 mm centres, supporting a corrugated iron roof (no ceiling) in a size of 140 x 45 in a non-cyclonic area, wind classification N1/N2. The roofing material could weigh up to 10kg/m2, which would cover common steel roofing materials. Other combinations of materials can be assessed using the design tools referred to above.Skillion roof
Answered on 15-01-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.