I have yet to build my coop, but one thing I'm going to do is build "square". By this I mean not a rectangle. I'm planning on building my hen house and run both square.
If you have the room this is the most economical, efficient design. The trick is the length of the perimeter where the fence wire, plywood, posts, etc., will be needed. It really pays off for runs while with house the roofing and flooring lessens the impact of it...
4x8=32 sqft with a perimeter of 24 feet
8x8=64 sqft with a perimeter of 32 feet
8x12=96 sqft with a perimeter of 40 feet
12x12=144 sqft with a perimeter of 48 feet
For a house 20% more material would yield ~50% more floor space
10x12=120 sqft with a perimeter of 44 feet
12x12=144 sqft with a perimeter of 48 feet
100x25=2500 sqft with a perimeter of 250 feet
62.5x62.5=3906 sqft with a perimeter of 250 feet
For a run this would add over 50% to the square footage for the same amount of fencing and posts!
Check my math, but square is cool.
If you can build square...go for it!
Ed