I am having bids done for a new roof on the garage of our condo building. For purposes of assessing cost, I need to know exactly what is considered the "surface" of the roof. I know there must be some standard agreed language. The surface of the roof includes??? What?? What is the surface and what is the rest of the roof? Forgive me for not knowing any of this, but I am only now becoming "roof aware."

Thanks in advance for any suggestions.