Puybaret, thanks for the reply and link.

I've learned a fair amount since I posted my question but I'm still unclear on how to precisely locate an interior wall. Specifying the length and width of walls is simple enough but what I can't seem to do is indicate that an interior wall must be, for example, 28" away from some other wall. As a hack, I've been creating dimension lines to manually measure the distance between various objects but is there not an easier way? The perimeter of my floor plan is half-filled with these manually-inserted dimension lines.
thanks.