A fix for a major problem: exterior walls that are bowing outward. Two weeks of work in the basement, meanwhile, has lowered the floor by several inches; the radiant heat-insulation system is installed; and it's shown how the roof is under-structured. In other events, Norm revisits a Charlestown townhouse featured on the show 14 years ago. In the second half: citrus greening, a disease killing citrus trees in Florida, is discussed. Also: replacing a vinyl peel-and-stick floor with ceramic tile.