The answer leads to wider issues. Deflection was small in either direction, but the constant movement reopened cracks and strained flashing between roofs and walls, a delicate joint in any building. When the flashing opened up, even inconspicuously, water penetrated, then threaded through interstices, and issued far from the point of entry as distressing leaks. There were seventeen such areas when we first moved in. Not unlikely, but damaged flashing was more surely responsible.
Some leakage still occurs, and now a concerted effort is under way to rework all flashing.
To do this and yet maintain the neatness of the exterior will be a challenge. A Frank Lloyd Wright Country House , pp.