Hal:
The
20' wide 1-1/2 story plans have a 10' high side wall that is notched out for the loft floor. Depending on what ceiling height you want on the main level this will give you a 2' or more kneewall in the loft. Some folks who build a full length loft have gone for a higher sidewall in the loft by using 12' tall 2x6 wall studs. You don't want to do this if you plan for part of the upper floor to be open to the living space below. (10' tall max on unsupported walls.)
The loft floor as drawn in the plans is an open undivided space. This can be laid out in many ways. If you wanted a bath upstairs it would be a good idea to layout the wet wall to align with the lower bath 2x6 plumbing wall. You may need a shed dormer to get proper headroom in this space. Dormer drawings are included in the options booklet.
Also, as you choose to use the loft more as a full second floor, you may want to use the full sized "U-shaped" stair plan that is included in the booklet that comes with the plans. This is safer and easier to negotiate with an armful of laundry than is the cottage stair shown in the main floor plan.
