Detectorist Bob Phillips discovers a cannonball at the job site that may be a souvenir from the war of 1812. Norm shows Kevin the progress on the framing of the old Greek Revival house and the new connecting ell. Tom introduces Kevin to two carpentry students that are part of the This Old House 25th Anniversary apprenticeship program. Then Tom explains how he's built up all ten posts on the short side of the barn by using scarf joints to make the connections. Kevin travels to New Haven, Connecticut, to visit the Yale Building Project, a graduate class that requires Ivy League architecture students to learn by doing as they design and build a stylish urban home in a low-income neighborhood. Back at our project, Norm meets structural insulated panel expert Frank Baker to see another application for the SIPS technology - it's a fast way to install an insulated structural floor.