Boston Mayor Martin Walsh says the city needs to build 53,000 units of housing over the next two decades to accommodate a growing population and prevent low- and middle-income residents from being squeezed out of the market.

Part of the mayor's plan calls on the city's colleges and universities to build more dormitories, to free up off-campus apartments and save students from living in substandard rental units.

Walsh is calling on $21 billion in private and public construction to boost the city's housing stock by 20 percent and make room for a population expected to jump to more than 700,000 by 2030.

Part of the plan calls for loosening zoning restrictions and providing incentives for building taller buildings. The plan also calls for encouraging development around public transportation hubs.