how do I calculate roof slope for carport

GDay all

I am about to build my skillion roof carport which is 7m along the lenght of the house and 5.5m across the driveway. In the plans the maximum roof slope is 5 degrees.

So how do I calculate the fall across the 5.5m. :?

I seem to recall a builder telling me there needed to be a 20mm drop for every metre of roof length. This would mean the roof fall is 110mm. But I would like to know how it is calculated so I don't exceed the 5 degree slope.

cheers and any advice - formulas and explanations greatly appreciated.
Dave


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