Developer Monadnock Construction and architecture firm Architects worked inch-by-inch to meet such requirements as a wheelchair-accessible bathroom within the small space.

Forty per cent of the units have rents set by affordable-housing programs topping out at around $1,500 a month, but market-rate ones can cost between $2,650 and $3,150.

About 20 people have applied for eight market-rate units so far, while more than 60,000 have entered a lottery for the affordable ones.

Mayor Bill de Blasio’s housing plan says Carmel Place and other projects show ‘developers can build compact units that are livable, safe, healthy’ options for small households.