The driveway base coat has been laid at the Concord, Mass., barn conversion, as has the brick walkway, and landscaper Roger Cook raised the grade near the front door to accommodate a ramp, should one become necessary. Meanwhile, Cook and host Kevin O'Connor select plants for the yard. And inside, contractor Tom Silva and carpenter Norm Abram build a base cabinet for the pantry, while tile contractor Joe Ferrante encounters problems in the bathroom. On “Ask This Old House,” Cook repairs a drip-irrigation system for a California-desert homeowner while Ferrante and plumbing-heating expert Richard Trethewey fix a suburban-Boston homeowner's leaky bathtub.