Work begins on the Carlisle, Mass., farmhouse with a barn-raising (sort of)--- workers jack up the barn so its foundation can be repaired. But first, landscaper Roger Cook clears land for jobsite parking and architect Jeremiah Eck displays a 3-D model of his design. On “Ask This Old House,” Cook mends fences (literally) outside the “This Old House” barn, plumbing-heating expert Richard Trethewey fixes an anti-scald mixing valve on a shower and contractor Tom Silva upgrades an old drill by installing a “keyless” chuck.