Master Interface Process
OSE's method for adding BIM house layers. A layer is defined by drawing a contour at the right height within FreeCAD. For Seed Eco-Home, the design works around the bottom edge of beadboard for house circuit design. See working doc .
For example, where do you design your electrical boxes? If you know the wall layout design, and you know that the electrical boxes are flush with the interior skin (beadboard) - and you know the height of the bottom of the electrical box - then you have defined where an electrical box goes on any given interior or exterior wall module.