Major structural work is performed on the Carlisle, Mass., farmstead project: 40-foot beams to support the barn deck are installed, as are I-joist floor panels and a SIPS wall system. But arborist Matt Foti has bad news about two trees on the property, and that's not the only bad news. On “Ask This Old House,” projects include a window box and backyard resodding. Also: “What Is It?”