The Housing Supply Expansion Act modifies prevailing wage requirements that apply to federally funded affordable housing construction projects. The bill changes how the Department of Labor determines and applies prevailing wage rates by allowing wage determinations based on broader geographic areas like metropolitan statistical areas rather than just individual civil subdivisions, and by updating survey methods to improve data collection and business participation. The legislation creates a Davis-Bacon Modernization Working Group composed of government officials and industry representatives that must submit recommendations within one year on whether residential wage classifications could apply to taller affordable housing buildings, whether prevailing wage requirements could be waived for certain projects, and whether the Bureau of Labor Statistics could determine prevailing wages using existing data instead of voluntary business surveys. These changes affect developers, construction workers, and organizations involved in federally assisted housing programs, with the goal of reducing construction costs to expand affordable housing supply. The bill includes no new federal funding but aims to streamline existing wage determination processes.