A new study put out in a report by Citizens Housing and Planning Council shows there are up to 210,000 basements and cellars across the city that could potentially be converted into legal apartments—enough to move the needle on the city’s housing crisis without pouring a single new building foundation. According to Sarah Watson Watson, deputy director of the organization,”there is a convincing scale to this, we’ve set out the major arguments for conversions and our recommendations about how a pilot program could be structured.”