Kevin arrives to find Tom solving a major problem with the house - the exterior walls are bowing out from the weight of the roof over 160 years. In the basement, Richard shows Kevin the result of two weeks of hand digging and a week of rough plumbing. On the third floor, Norm shows Kevin how the roof has been under-structured since it was originally built. Tom joins to get the first of two massive LVLs tucked into the pockets in the brick sidewalls and fastened in place. Norm revisits the townhouse TOH renovated in Charlestown 14 years ago. Back at the project house, Tom shows Kevin how he's going to open up the back wall for the new bump out. In the second half of the hour, on ASK THIS OLD HOUSE, Roger heads to Florida to learn about citrus greening, a disease that's killing citrus trees across the state. Tom replaces an old vinyl peel-and-stick floor with ceramic tile. And the guys ask, "What is it?"