Measurements

[crisw]

I have read many times that buildings should be laid out in increments of 2' or 4' to save materials. Now that I have all the walls in my plan where I want them, I want to make the nudges needed to get those measurements. However, I am not sure of which dimension is the most crucial! Should I be measuring the dimensions to the outside walls? How should I set up my dimension defaults box? Thanks!