There are up to 210,000 basements and cellars across the city that could potentially be converted into legal apartmentsenough to move the needle on the citys housing crisis without pouring a single new building foundation.

But the legalization process is fraught with political and technical pitfalls, which is why a study released Thursday suggests that the de Blasio administration should start with a pilot program to capture the lowest hanging fruit: the roughly 38,000 basements in single-family homes that could be converted without any major changes to city or state law.

“There is a convincing scale to this,” said Sarah Watson, deputy director of the Citizens Housing and Planning Council, which authored the report. “Weve set out the major arguments for conversions and our recommendations about how a pilot program could be structured.”

Read more in Crain’s New York Business.