A class-action lawsuit against manufacturers of hardboard is still in its early stages (Eight-Penny News, 3/96). Plaintiffs claim that the material has inherent limitations as siding, while manufacturers respond that most problems stem from faulty installation or maintenance. On closer scrutiny, both sides may turn out to have legitimate points. While hardboard is particularly vulnerable to moisture, builders or homeowners can make matters better — or worse. Understanding hardboard. Hardboard is made of wood pulp: fibers, bundles of fibers, and fiber fragments produced by blasting wood chips apart with a steam-pressure vessel, or grinding the chips between giant steel plates. In a hardboard plant, the fibers are formed into boards under high heat and pressure. In "wet-process" hardboard manufacture, a slurry of wet pulp is pressed and heated to squeeze out water