Building Philosophy The Apple Corps Guide to the Well-Built House by Jim Locke; Houghton-Mifflin Co., Boston, Mass.; 267 pages; $9.95, paperback. At other times I found Locke to be literally in error and even maddeningly unsupportive of his own convictions. For instance, he describes concrete as "porous," when if properly mixed and cured, the stuff is almost watertight. He faults "construction films" (e.g., Tyvek) for being "heavy" when a 10-foot roll can easily be carried with one hand. And what does he mean when he says extruded polystyrene insulating board costs "$600 per square inch of thickness?" Locke says the Apple Corps uses crossbridging between joists to "increase the solidity of the structure"—seeming unaware that tests have shown that bridging or blocking contribute little