Först Consulting Group evaluates construction work against the specific published authorities that govern the project’s jurisdiction and date, rather than against opinion. Commonly applied authorities include the International Residential Code (IRC) and International Building Code (IBC) in the edition adopted by the local jurisdiction; the National Electrical Code (NFPA 70 / NEC); the International Plumbing Code (IPC) and International Mechanical Code (IMC); the International Fuel Gas Code (IFGC); manufacturer installation instructions (which the IRC makes enforceable by reference); the NAHB Residential Construction Performance Guidelines; and applicable state statutes and county amendments. In Virginia, work is measured against the Virginia Uniform Statewide Building Code (USBC) and DPOR contractor regulations at 18VAC50-22. Identifying the correct adopted edition matters because code requirements change between cycles.