Hi Devine,

Here is a design of a Pavillion we will be installing at a pool facility in Fairfax, VA just outside of Washington DC in September. It is 4.8m x 7.2m (16'x24') with a 4/10 pitch (22 degree) common rafter system of 100mm 100mm (4"x4")rafters that are a 600mm (24") on center, and span approximately 2.4m (8')

Your design just needs a little tweaking to work, even with square rafter stock in the smaller dimensions (4x4 to 5x5.) I would have a PE check out the final design if you are not certain of your math. There is a lot that can be considered on roof loads, including pitch, and deck diaphragm configuration that can influence load capabilities, such as double layering of plywood (should you go the sheet good way) spline, toggle, or t&G board stock.

Regards,

jay