The Department of Buildings will hold a public hearing at 3 p.m. Fri., March 6, in the department’s third-floor conference room, at 280 Broadway, regarding a new, formal, 30-day public challenge period for new projects and major changes to new projects. The changes are scheduled to become effective Mon., March 9, presumably after Buildings Commissioner Robert D. LiMandri spends the weekend looking over the testimony from the Friday hearing.