Being 'in the game', I often design as I go. There are many givens, such as a normal door height is 6'6", wall heights 8', 10', 12' etc., roof slopes 15°, etc.etc. in nice round multiples. Get where I'm coming from.
I designed this Engine Shed so I could build it with minimal material, and wastage. The scribed siding came in 24"x3" size. That's 48' by 6' in ½" scale. Stack two pieces, and I've got a bit of raw material, effectively 48'x 12'.
OK, so what about the 'plan'. Well 48' has to be the perimeter of the building, and I've got a height of 12' to play with, i.e. maximum height. So, I sttled on a 10' stud. That's the wall height for the untechnical ones out there. The extra 2 feet was for the peak of the roof. You will see there is a workshop annex to one side, this has a stud of 8', allowing for a 2' roof fall from the 10' wall that ain't there. Oh, we are talking of a Gn15 shed here, but the principles are still the same.