Work winds down at the Concord, Mass., cottage as host Kevin O'Connor reviews exterior details with architect Holly Cratsley. Inside, granite kitchen countertops are installed, as are stain-resistant carpeting, custom windows (with stained glass) and closet systems. Meanwhile, O'Connor seals stair treads with polyurethane while carpenter Norm Abrams visits a polyurethane factory in Flora, Ill. On “Ask This Old House”: contractor Tom Silva shows a Sudbury, Mass., homeowner how to snake wire through an exterior wall; and landscaper Roger Cook shows O'Connor how to plant a magnolia tree.