Overview: The basement of This Old House's Charlestown project continues to be transformed into two bedrooms for the rental unit. To ensure the space remains warm and damp-free, close-cell foam is sprayed against the exterior walls. Upstairs, in the Beliveaus' living room, host Steve Thomas meets with plaster restorer Rory Brennan to learn about the process of saving the old horsehair plaster and vintage ornamental details.