Harry Muscle wrote:

the winter (I'm in Ontario, Canada). I still haven't finalized the
size, but it's gonna be either 10x15 feet or 12x12 probably. My first
question is to do with the roof ... do I need an attic in such a shed?

Seen quite a few good tips so far but haven't seen this:

Rethink your sizing so that each side is divisible by 16" to prevent
waste and the hassle of having a fraction of a 16" stud space at the end
of the wall -DAMHIKTg

Think about it. Doesn't it seem easier to build and cut lumber for a
12'x12' shed than a 10'x10'?

As for size, be guided more by the allowable room in which to build than
by the cost today. After your raise next year that extra 100 sq' or 150
sq' will make you smileg