Figure 3. This is an annotated, revised, and schematic version of Silman’s “Attic Floor Existing Framing” plan, showing not only how columns and girders are displaced between the north-south bracing walls, but how the attic joist-rafter elements, considered as rigid free-bodies, have rotated and displaced laterally. Locations of maximum column displacement and maximum attic joist rotation occur toward the middle of the north-south bracing walls: Attic joist “A” (at the bracing wall or frame) is horizontal, with no apparent rotation, whereas attic joist “B” shows significant rotation, with its northern end 1.5 inches lower than its southern end. This rotation, made possible by the “hinged” connection to the inclined Mansard supports, is easier to visualize by examining the section in Figure 4. (Annotations and revisions by J. Ochshorn, April 2018)